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Old 05-17-2007, 07:02 AM
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Electric Speedometer Senders

Be warned this is a long post. My question once I get to it will actually have several parts. I have the Wings Gauges by Stewart Warner with the electric speedometer. The speedometer was working fine than it quit, so I assumed the sending unit (pulse generator) went out (the rest of the gauges are still working and the speedometer even goes to zero when I start the car, so it's not a power issue). I started looking for a replacement and being the cheapskate I am, I was not happy to see the replacement sending unit was $100. So I decided to dig a little deeper. The SW sending unit has 3 wires (12 volt supply, ground, and wire to speedometer) and it's listed as a 8 pulse per revolution. I've seen some other sending units (Dakota Digital) that are the 8 pulse per rev, but they only have two wires. Then I've seen some sending units (Autometer) that have the 3 wires like mine but they're listed as 16 pulse per revolution. My SW Wings Speedometer has the dip switches on the back that I can use to calibrate the speedometer. In the instructions it states the sender generates 8 pulses/rev and the normal calibration is 8000 pulses per mile. Also in the instructions the have a speedometer programming chart that shows different dip switch settings for different pulses per mile. One setting shows the 16000 pulses per mile which I would assume would work for a 16 pulse per revolution sender. Now finally to my question. Will a two wire 8 pulse/rev sender work or do I need the 3 wire sender. If I need the 3 wire sender can I get the cheaper 16 pulse/rev sender and just change the dip switches on the speedometer. I know the easy answer is just get the SW sender and be done, but as I stated I'm cheap and I'm always looking at why things work like they do and how I can do the same thing but in a different way. Thanks again for any help and I apologize for the length of the post.

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Old 05-17-2007, 07:07 AM
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I'm pretty sure the 16 pulse per rev one would work as long as the output voltage was the same, i.e. 5 volts or 12 volts or??

Have you called Dakota?
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Old 05-17-2007, 08:09 AM
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I haven't called Dakota yet. I guess my other question is how does the 2 wire sender work, does it generate a voltage to send to the speedometer? On the 3 wire sender it has 12 volts coming in and then it sends a pulse to the speedometer. I was curious as to reason some senders are 2 wire and some are 3 wire and does the speedometer really care as long as it sees a pulse.
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Old 05-17-2007, 08:51 AM
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Does your speedometer have a manual calibration feature?

With my autometer, I can push a button. Drive exactly one mile and push the button again and it is calibrated. If you can do this, seems like the pulses per revolution wouldn't matter as long as the sending unit would wire up to your speedometer correctly.
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Old 05-17-2007, 08:58 AM
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My Stewart Warner Wings Speedometer is pre-2006 and has the dip switches on the back of the case. I can change the settings to change the pulses but I didn't know if it was as simple as that.
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Old 05-17-2007, 09:45 AM
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The three wire most likely supplies a voltage on the 3rd wire for a pulse, whereas the 2 wire is most likley just a switch closure to ground.

I would stick to the three wire version
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Old 05-17-2007, 06:04 PM
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Doc here,

A Pulse generator Transducer works from a signal generated by either an opto Isolator or a magnetic switch mounted around a rotatory magnet or Make/Brake light source.

An opto Isolator requires POWER, GROUND , and SIGNAL to operate..(Three wire) The Magnetic switch only requires signal in / Signal out..no power is needed to operate the electronic Isolator. (2 wire)

Last time I looked through the transducer book, IIRC, they came in two flavors..GM (All) and the rest of the world..But this may also be manufacturer specific..Check your guide for that data.

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Old 05-17-2007, 06:20 PM
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Thanks for the reply. I should have stated this is on a 700r4 in a street rod pickup. Like I said my 3 wire 8 pulse unit died. A friend of mine had a 2 wire 8 pulse unit that he got with either his Dakota digital gauges or the cruise control unit. I decided to try it out, it works, but it doesn't start right at first when I start driving and then all of a sudden the speedometer jumps up to 40 mph and then it looks like it registers pretty close, but it's not right either. So I know it's not right and guess I'll have to try another fix. Like I said in my first post, I really hate to spend $100 just on a sender, but it might be my best option.
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Old 05-19-2007, 10:34 AM
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Problem solved. I found on the Stewart Warner Speedometer there are two terminals that you can hook the wire from the sender to, one marked AUX and the other marked SIG. With the 3 wire sender I used the AUX terminal, per the instructions from SW. When I first hooked up the 2 wire sender I used the AUX terminal, the speedometer would work but only when you went faster than 30-40 mph, so I knew something wasn't right. I decided to hook the wire up to the SIG terminal to see what would happen and now everything works correctly. Best of all it didn't cost me anything except a favor to my buddy that had the extra sender. Also I can buy a 25-30 dollar sender instead of the 100 dollar sender if I have trouble again. I like it when things work out like that. Thanks to everyone for their help.
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Old 05-20-2007, 02:10 AM
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Doc here,

KEWL! Glad to hear it's fixed!

Now, to pay back that favor to your bud... hopefully it won't be a backup on an engine pull at 2 AM in the morning..

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Old 05-08-2010, 02:53 PM
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Quote:
Originally Posted by oldcarguy36
Problem solved. I found on the Stewart Warner Speedometer there are two terminals that you can hook the wire from the sender to, one marked AUX and the other marked SIG. With the 3 wire sender I used the AUX terminal, per the instructions from SW. When I first hooked up the 2 wire sender I used the AUX terminal, the speedometer would work but only when you went faster than 30-40 mph, so I knew something wasn't right. I decided to hook the wire up to the SIG terminal to see what would happen and now everything works correctly. Best of all it didn't cost me anything except a favor to my buddy that had the extra sender. Also I can buy a 25-30 dollar sender instead of the 100 dollar sender if I have trouble again. I like it when things work out like that. Thanks to everyone for their help.

what wire did you hook up to the SIG post. I have the same problem hooked the gray wire to SIG post and black wire the the NEG post Speedo works but is jumpy at first?
James
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