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Topic Review (Newest First)
08-21-2006 05:02 PM
docvette
Quote:
Originally Posted by oldguy829
Sorry Doc, just can't check this off the list. I'm missing something basic I think. On the bench all is fine. Installed in the car - way off. I had the entire bezel on the bench, hooked up to a car battery, sender in water, etc. When I installed it I even used the same wire from the unit to the sender (with the extra resistors soldered in line). When I start the car, cold, it reads 180 degrees and pegs in a couple of minutes. Why would it change in the car?
My first thought was poor ground, but I've beat that idea to death.
Doc here,

I would tend to concur on the bad ground..

Try (if you haven't already) running a ground wire from the tank to the gauge to the sender body and see if the situation doesn't go back to the way it tested on the bench..

Doc
08-21-2006 08:33 AM
oldguy829
6v 12 v help

Sorry Doc, just can't check this off the list. I'm missing something basic I think. On the bench all is fine. Installed in the car - way off. I had the entire bezel on the bench, hooked up to a car battery, sender in water, etc. When I installed it I even used the same wire from the unit to the sender (with the extra resistors soldered in line). When I start the car, cold, it reads 180 degrees and pegs in a couple of minutes. Why would it change in the car?
My first thought was poor ground, but I've beat that idea to death.
08-11-2006 05:54 PM
docvette
Quote:
Originally Posted by oldguy829
Well Doc. With your kind and generous assistance, I would like to continue my education. I am making progress with the temp gauge, here is where I am.

1. On the bench, I have used a variety of Ohms resistors to plot the curve of my temp gauge.


Quote:
2. Using a pot of water that I can both control and record the temp of the water, I have tracked the ohms resistance present in 3 different sending units through a variety of temperatures from 100 to 212.

(all 3 had the approximate high and low values of my gauge, but varied in the linear curve)
Linearity errors are to be expected..the best you can do, is work the resistance Around the "Center" or "Working" part of the gauge, and know that the ends have some + / - errors...(or replace it for a better linearity gauge.)

Quote:
3. (This is where I previously hit the wall ) When I hook up a sender to the gauge and the heat the water, the gauge does not respond properly.

For example, at 50 ohms resistance the gauge reads about 130 degrees. But when the water reaches about 145 degrees (where the sending unit has a reading of about 50 ohms)

The gauge starts to climb until it reads about 190. With the water temp above 145 degrees, it just pegs the gauge.
You DO have a good ground to the sender unit body , CORRECT? (required..)
Quote:

Last night (out of frustration mostly) I added ohms resistors to the sending unit wire. It worked! With a resistor, any resistor, in the line - the gauge would give me a stable reading that was in line with the bench test guidelines.
This was where I was headed if you could not match units..you just went on a step farther and solved it.

Quote:
I finally settled on 7 Ohms as the necessary resistor for one of the sending units. So my question is... What gives??
First, the 7 ohms you read, may not be 7 ohms Et and Al..you must add the resistance of the sender AND the resistance of the gauge circuit to get a total reading..which may just "Happen to be in the proper range you require for close to accurate readings..

The old sender over time may have changed value from mechanical wear, and not you have added that what was missing...
Quote:

Why does the resistor in the line stabilize the feedback from the sender?
Did the original 41 sending unit have something that is missing from modern units to accomplish this?
Simply because you are changing the value of the circuit around the sender/gauge, by the addition of resistance..The Same would apply , say, with a light bulb, by adding resistance to the filament , you can come up with different combinations of bright and dim..

Quote:
Now for step 4. To permanently install a 7 ohm resistor in the sender line.
This leads to my next question. I didn't have a 7 ohm resistor, but in experimenting came upon another mystery.

When I wire 2 - 10 ohm resistors end to end, it creates 20 ohms of resistance. When I wire 2 of them together side by side, it creates 5 ohms of resistance?

When I wired a 10 and a 22 side by side, I got 7 ohms of resistance?

Can you explain this?
Yes, I can..But I'd have to do a chapter on series, parallel, and series/Parallel resistances here, And this post is a major read as it is.. , best not to confuse more than one thing at a time ..

It would be better for you to do an online search for basic electronic theory, under Resistance , and it's properties..OR: get a basic electrical / Electronic book and read that chapter..

In Short, in certain configurations, resistances (series, parallel, series/parallel) become Additive, Divisible, or remain the same and wattage (usable current ) Doubles..or any three like resistances to ground will 1/2 the voltage..and so on..You find all your answers in that chapter..A good read should you be interested..

Quote:
I will be looking for a thermal shielded 7 ohm resistor today, but if I can't find one a 10 and a 20 wired side by side may be close enough. any problem with that scenario?

Thanks again Doc.
OK, since this post you have added more..so I'll add what I was going to tell you in the first postings a while ago..

If you can't Find the exact value Resistance you need to perform within the range you desire..figure the "RANGE" of resistance it operates within..For Instance, 0 to 100 ohms..and you need a 17 ohm resistor..you can try, 15 or 20, but if not close enough..go this way:

Find a "Linear Taper" Variable potentiometer , (A Volume control pot..) , within the range you require..In this case probably 0 to 500 ohms is as close as you'll find at the local rat shack..

Using Half the pot..Center wiper to the gauge, and either end tap to the sender..(this will effectively 1/2 the value of the pot..if it's 500 ohms, one end to center will be approx 250 ohms .. and so on..) Install on the sender line..power up the gauge and "Adjust" the "Volume Control" for the most accurate reading..Once satisfied..Glue the shaft at that point..and get a large shrink tubing to fit over the pot, shrink it down and tie wrap it out of the way..

The only thing you need to be aware of is the wattage of the pot as opposed to the resistor..If you are running a 1 watt resistor , you must use a 1 watt pot or higher..else you will let out the factory installed smoke ..and it won't function.

If all else fails for you, and I doubt it will, your on the right track..let me know, I can design a circuit for you that uses an op amp to control the gauge..but it will require some circuit card building and the Chip and some added electronic components to fabricate it..

Doc
08-11-2006 04:15 PM
larryblack Solder the resistors together and to the wires. Use a wire to the gauge so you can mount the resistors where you have room. They should not get hot but place them where they are not against something that might melt just to be safe.

Get some "SHRINK WRAP" from where you got your resistors. They should know what it is. If not Rad Shack has some or any local electrical parts house.

Shrink wrap is a tube you cut to slide over your resistors. Make sure it covers all exposed wire too. Use a heat gun or hair dryer and heat it. It will "shrink" down in size insulating the exposed wires and connections.

If you solder the wire to the gauge, you can put some shrink wrap over the connection to help keep corrosion from forming. Shrink wrap will present a much cleaner look than tape.

You asked about series and parallel resistors. There is a formula for determining total resistance. In series you just add them like you did and you get total resistance.

In parallel you have more than one current path. This actually reduces the total resistance of the circuit. The formula basically has you multiply the resistor values and divide that value by the sum of the resistor values. Any time you parallel any resistor with the same value you 1/2 it. If you have 3-10 ohm reisitors in parallel you have 10 divided by 3 or 3.33.

All gauges are not linear or move a specific amount with a specific change in what you are measuring. If you look at some temp gauges they change 50* in the first 1/4 arc and then move 50* in the next 3/4 of the arc. This is why there is sssssooooo many senders out there.

I applaude your tenacity to get your factory gauge working. I also see why Doc has such a stellar reputation for helping.
08-11-2006 02:31 PM
oldguy829
6v - 12 v help

Doc, can only find 1s 10s 50s in the 10 watt shielded resistors.
I wired 2 10s together (5 ohms resistance) and a 1 tagged on the end (series) and it reads 6 on the meter. It is within 10 degrees of actual and reads a touch high (which is better than low) so I think I am set.
any no-nos before I make this a permanent installation? don
08-11-2006 07:14 AM
oldguy829
6v to 12 v help

Well Doc. With your kind and generous assistance, I would like to continue my education. I am making progress with the temp gauge, here is where I am.
1. On the bench, I have used a variety of Ohms resistors to plot the curve of my temp gauge.
2. Using a pot of water that I can both control and record the temp of the water, I have tracked the ohms resistance present in 3 different sending units through a variety of temperatures from 100 to 212.
(all 3 had the approximate high and low values of my gauge, but varied in the linear curve)
3. (This is where I previously hit the wall ) When I hook up a sender to the gauge and the heat the water, the gauge does not respond properly. For example, at 50 ohms resistance the gauge reads about 130 degrees. But when the water reaches about 145 degrees (where the sending unit has a reading of about 50 ohms) The gauge starts to climb unitl it reads about 190. With the water temp above 145 degrees, it just pegs the gauge.
Last night (out of frustration mostly) I added ohms resistors to the sending unit wire. It worked! With a resistor, any resistor, in the line - the gauge would give me a stable reading that was in line with the bench test guidelines. I finally settled on 7 Ohms as the neccesary resistor for one of the sending units. So my question is... What gives??
Why does the resistor in the line stabilize the feedback from the sender?
Did the original 41 sending unit have something that is missing from modern units to accomplish this?
Now for step 4. To permanently install a 7 ohm resistor in the sender line.
This leads to my next question. I didn't have a 7 ohm resistor, but in experimenting came upon another mystery. When I wire 2 - 10 ohm resistors end to end, it creates 20 ohms of resistance. When I wire 2 of them together side by side, it creates 5 ohms of resistance? When I wired a 10 and a 22 side by side, I got 7 ohms of resistance? Can you explain this? I will be looking for a thermal shielded 7 ohm resistor today, but if I can't find one a 10 and a 20 wired side by side may be close enough. any problem with that scenario?
Thanks again Doc.
07-31-2006 05:15 PM
docvette Doc here,

The only thing the WATTAGE of the resistor will effect is it's ability to sink or transfer heat from it to it's surrounding area without burning itself up..you may always go higher on wattage if space is not a problem..

It's the ohmic value you must abide by..

Doc
07-31-2006 03:03 PM
oldguy829
6v to 12 v conversion

Hey Doc, got sidetracked with vacations etc. About the linearity on the temp gauge/sender issue. You recommended 1 watt (or 2 half watt) resistors. I noticed radio shack had some 10 watt resistors that looked nice and stout, with apparently a heat resistant shield, that would apear to be more durable under the hood. What is the effect of using 10 watt, rather than 1 watt, resistors in this application? don
07-06-2006 04:02 AM
docvette Doc Here,

OK, on the first post..

To make it simple..just strip the red wire from the solenoid that goes to some "mid~point " splice and tons of tape where the second red ties in..

In other words all that should be left on the alternator is THE BROWN wire and a Stub of the red wire from the top plug, next to the brow wire ...

NOW, run a 70 amp fuse link directly from the starter solenoid battery cable bolt, then attach a RED 10 gauge wire to it, route that to the alternator, at the bolt or + OUTPUT lug at the back..and cut the wire...

Next take your second red, The Regulator switching, route that from the plug to the area of the + bolt or lug on the back of the alternator cut that there....Strip both wires, and Get a YELLOW ring terminal, CRIMP BOTH wires into it, and bolt it on the + lug bolt...
Leave the Brown wire alone , it is the idiot lamp..

You need only one fuse link for this circuit as your running an equiv, circuit, through the same link using one wire.

OK, On the Sender..It is perfectly acceptable to "Pad" a range for linearity, SO long as the upper scale of temp is not off the map..
I.E..It does not go from 180 to peg...

and the errors are only a few degrees + / - actual, otherwise you might as well not run a gauge at all..just get a lamp..it would be as accurate.. (maybe) Point is..If it is way out of the ballpark..except for one "small range".. you run the risk of engine damage..

If it gives a Good range that you can live with , and are aware of the errors at certain points..get that value resistor..in a 1 watt version ( or 2 1/2 watts twisted and soldered together) and solder it in line on the sender wire. 1/2 watt will probably get a little warm..

Doc
07-05-2006 08:31 PM
oldguy829
12v to 6 v temp sending unit

We are making progress here Doc. Picked up another sending unit that was supposed to match my needed values. Wired it all up on the bench and, damn, it worked. Of course, we now get to talk about "linearity" (sp).
After chasing it up and down the range with my little 2 cup coffe maker and a candy thermometer, I narrowed down the problem. Not sure this is Kosher, but what the hell. I wired a 100 ohm resistor into the sender line and got an accurate reading from about 160 degrees to 180 degrees. At about 195 degrees I had to replace it with a 70 ohm resistor to get the right gauge reading, at 210 I had to drop to a 30 ohm resistor. [the specs on the sender were 450 ohms at cold to 30 ohms at 220, so the sender could be performing properly, just not linear with the gauge, is that right? ]
If you are going to tell me what I think you're going to tell me, speak slowly and use small words like you were talking to a child. skip that, todays kids would probably get it before I do. Just remember, the gauge has been modified once already. don
By the way, I had one of those spiritual moments, Just sitting there looking at a temperature gauge that was working.
07-05-2006 08:07 PM
oldguy829
12v to 6v help

OK Doc. Before I rip it's guts out, let me walk through it once. Never used this "quote" response, so bear with me.

Quote:
Originally Posted by docvette
Doc here,

OK, to Clean all that up, Strip out that wire..(except the brown wire..)

Install a fuse link at the Starter solenoid..70 amp. From there run One 10 gauge wire to the big bolt on the alternator..

From the top plug, locate the red wire there, and cut it long enough to reach the big terminal, and cut it and install a ring terminal, Bolt it to the big terminal.

The brown wire will remain the same.

You need only 1 fuse link this way on the alternator.

Starting with Red1 - this wire comes from the big terminal on the alternator and goes to a terminal block on the firewall (along the way it is connected to Red2). Here I unwrapped a lot of black tape and found a fusible link, hand twisted in line no less, and then it goes to the Battery terminal on the starter solenoid. I am to take this out and replace it with a new 10ga wire directly from the alternator to the solenoid, with a new 70 amp fusible link.
Red2 comes out of the alternator at the push in terminal (next to the brown wire) and after connecting with Red1 goes to the buss. I am to cut it off about 6 inches out and jump it over to the same terminal as Red1.


Next on the wire that brings power to the car..to the fuse buss (panel) , locate that wire (should also be on the solenoid, or single terminal at or near the battery..(It's the wire that when you pull it, the whole car goes dead from power..) Install a 70 amp fuse link there. This will protect the whole system..

I'm guessing you are talking about Red2, but the end away from the alternator. It connects to the buss on one end, and via it's connection with Red1, effectively goes to the battery terminal on the solenoid. this link would be missing when I pull Red1. You want this to be a direct link from the Buss to the battery terminal on the solenoid, with another 70 amp fusible link. Note; The positive Battery cable has a secondary lead (looks like 10 ga.) that is not connected. Would it be appropriate to run Red2 to this lead (directly to the positive battery terminal) with the fusible link? Seems like this is its ultimate destination, or does it need to be at the solenoid so it is connected to red1?
If I'm wrong about Red2 being the right wire, I'm lost. There is a heavy wire from the buss to the other terminal on the solenoid, but I thought that was coming from the ignition to the starter. Not a power wire like you describe. The only other large wire from the buss dissapears behind the engine and I think hooks up to the distruibutor for the ignition circuit. Again, power out, not in.

If I understand so far, then the brown wire for the alternator must be a feedback wire that tells it how many amps to put out? Where does it originate?

That "Wire" that you said was crimped..sounds like the fuse link..but scrap it all and do it as above. It's Cleaner.

Hope your next message doesn't start with " whoa - Stop" LOL.

As far as that gauge..

Try these guys,
Gauge restorations

Tell them you'd like to convert it to a volt gauge and also will need the gauge re~silk screened to match a volt gauge from amp meter..See if it is cost effective, and what they can do for you.

I'll give them a try. You apparently don't believe there is a safe way to use an amp gauge.
Doc
I'm going to send another reply, RE the temp gauge. I need to keep these issues separate. don
07-05-2006 02:34 PM
docvette Doc here,

OK, to Clean all that up, Strip out that wire..(except the brown wire..)

Install a fuse link at the Starter solenoid..70 amp. From there run One 10 gauge wire to the big bolt on the alternator..

From the top plug, locate the red wire there, and cut it long enough to reach the big terminal, and cut it and install a ring terminal, Bolt it to the big terminal.

The brown wire will remain the same.

You need only 1 fuse link this way on the alternator.

Next on the wire that brings power to the car..to the fuse buss (panel) , locate that wire (should also be on the solenoid, or single terminal at or near the battery..(It's the wire that when you pull it, the whole car goes dead from power..) Install a 70 amp fuse link there. This will protect the whole system..

That "Wire" that you said was crimped..sounds like the fuse link..but scrap it all and do it as above. It's Cleaner.



As far as that gauge..

Try these guys,
Gauge restorations

Tell them you'd like to convert it to a volt gauge and also will need the gauge re~silk screened to match a volt gauge from amp meter..See if it is cost effective, and what they can do for you.

Doc
07-05-2006 01:42 PM
oldguy829
12v to 6 v temp sending unit

Here we go again Doc. I just don't know enough to ask an intelligent question.
There are 3 wires coming out of the alternator, as in your diagram. (One off a terminal on the top, the other out of a push in connector along with the brown wire). 2 of them look like 10 ga. power wires (Red). They connect in the middle and it looks like one goes to the battery, via the starter, and the other to the main fuse block. (guessing here cause it goes into a large harness). When I say they are connected in the middle, literally, about 2 feet out of the alternator it looks like the insulation was pulled back and the 2 wires are clampled together with a big staple(?), wrapped in electrical tape, and then both continue on) Guess I misunderstood again. I thought one sent power to recharge the battery and the other to the system based on demand. That's why I was puzzled to see them connected together. (also thought this was an example of parallel wiring - which is still a mystery to me).
So. I will install a 70 amp fusible link in the wire coming off the solenoid. Your diagram showed 2, so I wondered where to put the second, since I don't have the typical horn relay.
Reason I ask which side to put it on, based on my assumptions above - I assumed the lead to the fuse box would not carry as much power as the line to the starter/battery, so it might be safer, but I don't know what the hell I'm talking about. . Yes, I can see how a defunct gauge would shut you down.
I've attached a picture of a gauge. Think I might find a volmeter gauge I could sub in for one this size and shape? Don't know when they went to voltmeters, but from about 55 on they seem to favor round gauges, or idiot lights. I could probably swap out the face plate to make it look OK. I really wanted to avoid some aftermarket gauges hanging off the dash.
thanks again, don
07-05-2006 01:10 AM
docvette
Quote:
Originally Posted by oldguy829
Well Doc. I did all those tests and came up blank, so I pulled it out and went back to the bench. It is definitely the gauge. Funny it didn't do it the first time I ran the resistance tests, but it is doing it now. Maybe that original voltage reducer didn't reduce enough and messed it up.
I'll let you know how I make out in a day or two.
That's pretty rare to find the gauge inaccurate..usually it is operable or not..but good catch..let me know how the new one works out!

Quote:
In the meantime, what about the amp gauge? It works, but is not hooked up. I've heard not to use it, and others who have had no trouble. i don't know of an aftermarket volt meter i could substitute into the pod. Got any thoughts on using the original?
I Don't like them, never did..they are dangerous in my opinion..When you have full battery potential , that is hot 24 / 7, 365....at the dash board and wires carrying it through the firewall..that you can drop a tool on, or catch your watch band..and burn holes in the metal..and maybe injure yourself..PLUS on most..If the shunt burns out in the gauge..your powerless..

Some will tell you "I've used them for 30 years, Never had a problem.." It only takes one time...to go tragically wrong...


Quote:
If so, Since my system is wired in parallel (I assume that's what it is since my two alternator wires are connected in the middle) can I hook the gauge in one side, or do I have to split them to wire it in in series?
I don't understand what you say when you say it is wired two in Parallel? Do you have 2 battery's? Two systems or what? If your referring to 12 volt / 6 volt..you are not feeding both separatly..(at least I would hope not..) If so you are overcharging the 6 volt buss..

The Amp gauge will always install between where the battery bolts to the source (like at the starter, ) and the load, the WHOLE car where the fuse buss wire connects at the starter solenoid....Current will go through the meter on to the car ..to be effective..


Quote:
According to AZ, my alternator was putting out 52 amps under the load test. I assume that is the combined output from both sides? Also hope to add A/C soon, so factor that in.
There should be "No two sides.." THERE SHOULD BE ONLY ONE OUTPUT from the alternator going to the battery terminal at the solenoid...anything else is something different.


Quote:
Also, I can find no fusible links in the system. Your diagram shows one on each leg. Should they be closer to the battery, or closer to the alternator? What amp rating would you recommend?
Fuse links were not installed at the factory until after 1970..so it's not surprising you didn't find any..With your current system, a 70 amp link should be fine..your alternator is probab a factory 63 amp unit. The fuse links will always install at the battery end of the circuit or at the solenoid...ALWAYS INSTALL THEM IN THE ENGINE BAY NOT INSIDE THE CAR...

Quote:
BTW, you mentioned running 2 busses. 12 v and 6 v. Not sure what that means, cause I don't know what a buss is. Everything on the car is 12 v, except the gas and temp gauge.
A buss is a system of wires that joins together at a common fused point..one main power wire in to a brass bar...and several smaller FUSED outputs coming off that bar..a split system is a 6 volt bar and then a 12 volt bar...separate from each other.


Quote:
Doc, is there any way to repay your kindness here?
Yes there is...do your wiring safely, and then, enjoy your rod when your done!!

Doc
07-04-2006 09:54 PM
oldguy829
6v to 12 v help

Well Doc. I did all those tests and came up blank, so I pulled it out and went back to the bench. It is definetly the gauge. Funny it didn't do it the first time I ran the resistance tests, but it is doing it now. Maybe that original voltage reducer didn't reduce enough and messed it up.
fortunately, the car came with a spare in a box of stuff. It's an after market, but pretty close. It has been modified with what looks like some resistors soldered to the field terminals, so of course the values are different, but I can handle that. I'll let you know how I make out in a day or two.

In the meantime, what about the amp gauge? It works, but is not hooked up. I've heard not to use it, and others who have had no trouble. i don't know of an aftermarket volt meter i could substitute into the pod. Got any thoughts on using the original?
If so, Since my system is wired in parallel (I assume that's what it is since my two alternator wires are connected in the middle) can I hook the gauge in one side, or do I have to split them to wire it in in series?
According to AZ, my alternator was putting out 52 amps under the load test. I assume that is the combined output from both sides? Also hope to add A/C soon, so factor that in.
Also, I can find no fusible links in the system. Your diagram shows one on each leg. Should they be closer to the battery, or closer to the alternator? What amp rating would you recommend?
BTW, you mentioned running 2 busses. 12 v and 6 v. Not sure what that means, cause I don't know what a buss is. Everything on the car is 12 v, except the gas and temp gauge.
Doc, is there any way to repay your kindness here?
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