[rapsag]

I have a custom built car (Chevy 350 drive train) with an auxiliary fan 130 watts at the front of the radiator. It is just set up with a manual toggle switch at the dash and powered by a 14 gauge lead from a hot terminal under the dash. There is a 25 amp fuse in the line. No relay. When I flip on the switch, the wire and fuse will gradually get hotter and hotter until almost untouchable. I always have switched it off at that point (usually don't need the cool fan for long anyhow), but have never let the fuse blow, which I am sure it would do. The toggle itself does not get as hot in comparison to the fuse and wire leading to it so I think it can handle the heat. The fuse in on the battery side of the switch which I assume is correct.

So what may be the problem? Poor ground from the fan? I know that having a relay is desirable but would that change the problem? Need a heavier gauge hot wire? Hot wire directly from the battery? Any advice appreciated.
rap

[docvette]

Originally Posted by rapsag

I have a custom built car (Chevy 350 drive train) with an auxiliary fan 130 watts at the front of the radiator. It is just set up with a manual toggle switch at the dash and powered by a 14 gauge lead from a hot terminal under the dash. There is a 25 amp fuse in the line. No relay. When I flip on the switch, the wire and fuse will gradually get hotter and hotter until almost untouchable. I always have switched it off at that point (usually don't need the cool fan for long anyhow), but have never let the fuse blow, which I am sure it would do. The toggle itself does not get as hot in comparison to the fuse and wire leading to it so I think it can handle the heat. The fuse in on the battery side of the switch which I assume is correct.

So what may be the problem? Poor ground from the fan? I know that having a relay is desirable but would that change the problem? Need a heavier gauge hot wire? Hot wire directly from the battery? Any advice appreciated.
rap

Doc here,

Your courting a fire in the making..

!4 gauge wire is way under rated for the draw your fan (s) are pulling..for starters.

The switch is most likely under rated as well..most "off the shelf" switches are rated at about 5 amps continuous contact ratings..

You need to install a relay, and 10 gauge wire.

A Fan may "Spike" many times it's rated value under certain conditions. Start up for one..That current that is required for the fan to overcome gravity..Rotor lock is another (a plastic bag sucked up off the roadway) , It can cause multiples of it's regular draw..Obstructions to the air flow..the possibilities are endless..

• Coil power to your switch now.
• Coil ground to a good bonded hard ground.
• 10 gauge wire from a Proper fuse link Directly from the battery or solenoid to the normally open contact on the relay.
• 10 gauge wire to the fan motor from the relay center wiper.
• 10 gauge wire to a good hard ground from the motor.

This will end your heating issues, it will deliver more power to the fan motor, be properly fuse linked, and your car will be less likely to catch on fire.

Doc

[rapsag]

I was not correct on the fuse set up. There is a fuse on the battery side of the switch which is 25 amp. I also then found a 25 amp fuse on the output side of the switch, and it is this fuse and the switch that heats up. I assume because it is on the output side. I checked the ground and found it grounded to chasis through the radiator frame (also not good?).

Doc, thanks for the prompt reply, and I will do just as you suggest. Please explain:
"Coil power to switch now."
"Coil ground to a good bonded hard ground"
Are you referring to the Relay Coil?

Also, I am not sure of the gauge of the original fan wires, but they don't look like 10 gauge. Will a soldered splice with 10 gauge as close as possible to the fan be OK? (I can't get to the fan itself, as it is in never, never land in front of the radiator and behind the grill).

And also, the battery ground cable is bolted to the block, would that place fit your description of a 'bonded' hard ground?

Lastly, will I still be able to power the relay with direct twelve volts (always on) so I can use the fan to cool down after engine is shut down. Don't want to use a thermostat.

Your answer will as always be appreciated, and I will be able to get busy with the above answers, (sorry for so many questions).
rap

[rapsag]

Got a relay, 30 amp. (no hang up tab was available). There are 4 terminals.
Correct me if I am wrong:

1:Terminals #85 and #86 are the coil terminals and polarity is not an issue?
Should I put a smaller fuse in the battery side lead to the coil?
2: Terminal #30 is the power in tab (battery side) and must be fuse linked
with say 25 amp fuselink.
3: Terminal 87 (which is turned 90 degrees from the other 3) is the power out
to the fan.
10 gauge wire on the high amp side. And is 14 gauge ok on the low amp side as I have some available. I plan to place the relay in the engine compartment as close as possible to the fan, so as to shorten the high amp wire length. Then will run the low amp switch wires from the dash. All will be routed away from the exhaust areas (no problem)

Am ready to fly upon your approval or correction of the above.
Yes I am compulsive, but it pays. rap

[docvette]

Originally Posted by rapsag

I was not correct on the fuse set up. There is a fuse on the battery side of the switch which is 25 amp. I also then found a 25 amp fuse on the output side of the switch, and it is this fuse and the switch that heats up. I assume because it is on the output side.

Fuses will not stand up to the spike issues of a motor, that open as soon as the current exceeds the rating of the draw..even a slo~blow will open up..Always use a fuse link..They MUST heat up and "Burn" for some time before they will open..a Fuse can leave you without a fan and in an overheat in traffic..

I checked the ground and found it grounded to chassis through the radiator frame (also not good?).

Good Grounding for your car:

Run a properly gauged Ground cable from the battery to any handy bolt at or near the starter, From that same bolt get a Battery cable at the parts store, that has two 3/8 ring terminals on each end and attach it there and to the Frame.

Next get some 10 gauge wire and ring terminals and run that from your bolt on the block to the Firewall, and another to the Alternator bracket or mount bolt.

Next get some Wire Braid, (Radio Shack) and install braid from the radiator support to the frame, Fenderwells to frame , hood to firewall, Doors to door posts, gas flap to body, tailgate / Trunk to body.

At each point the wire is grounded, Burnish ALL the paint and grease off to bare metal. Use a proper star-washer and lock. Use sheetmetal or Tech screws where no screws are available.

It sounds like a lot of work, but after you assemble all the parts, it's only a few hours to do..and you'll end up with a system that will work reliably for many years to come..and can eliminate that from your troubleshooting list.

Doc, thanks for the prompt reply, and I will do just as you suggest. Please explain:

"Coil power to switch now." <--This will be to the switch from the fan as it stands now..to the relay coil.

"Coil ground to a good bonded hard ground" <---the other side of the relay coil to a known good ground/body part, burnished surface and a star-washer.

Are you referring to the Relay Coil?<---Yes

Also, I am not sure of the gauge of the original fan wires, but they don't look like 10 gauge. Will a soldered splice with 10 gauge as close as possible to the fan be OK? (I can't get to the fan itself, as it is in never, never land in front of the radiator and behind the grill).

I would cut as close to the motor as possible, install ring terminals and a 2 terminal terminal strip..to the radiator support..10 gauge out from there.

And also, the battery ground cable is bolted to the block, would that place fit your description of a 'bonded' hard ground?

Read "Good Grounding" above ....

Lastly, will I still be able to power the relay with direct twelve volts (always on) so I can use the fan to cool down after engine is shut down. Don't want to use a thermostat.

Yes, just wire it as above...Power to the relay from the switch, and hard ground to the battery or body.

Your answer will as always be appreciated, and I will be able to get busy with the above answers, (sorry for so many questions).
rap

No problem!

Doc

[docvette]

Originally Posted by rapsag

Got a relay, 30 amp. (no hang up tab was available). There are 4 terminals.
Correct me if I am wrong:

1:Terminals #85 and #86 are the coil terminals and polarity is not an issue?

Should I put a smaller fuse in the battery side lead to the coil?

Just substitute "temp sender for "Ground" in your case..Polarity is NOT an issue..and the fused side of the coil, need only be, 1 amp..

2: Terminal #30 is the power in tab (battery side) and must be fuse linked
with say 25 amp fuse-link.

This will be the FAN side..Always leave the the center wiper as the chosen device, not power..that way things can't short to the normally closed contact..like tools..

3: Terminal 87 (which is turned 90 degrees from the other 3) is the power out
to the fan.

No this will be the linked power..

10 gauge wire on the high amp side.

On the FAN circuit both sides of the CONTACTS are high draw.....

And is 14 gauge OK on the low amp side as I have some available.

14 Ga on the CONTROL circuit side, there is no "Low draw" on the relay contacts both sides will draw about 30 amps.. (relay coil only, will draw about 1 amp...)

I plan to place the relay in the engine compartment as close as possible to the fan, so as to shorten the high amp wire length. Then will run the low amp switch wires from the dash. All will be routed away from the exhaust areas (no problem)

BOTH sides of the relay contacts will be high draw sides..battery and fan..so both sides must then be 10 gauge (at least to the point of the fan wires you need to cut and put on a terminal strip)

The LOW draw side will be the CONTROL wire side, (the coil)

Am ready to fly upon your approval or correction of the above.
Yes I am compulsive, but it pays. rap

Make those small corrections and use the diagram above and you'll be fine..

Doc

[rapsag]

Thanks, will do. This relay does not have the center lug (normally closed).
Will report results just for the record.
rap

[rapsag]

Finished this pm. What a difference a little wire will make. Relay is under hood up front and only got as warm as the other non- engine things. Wires stayed cool. Happy camper. And thanks Doc!
rap

[docvette]

Doc here,

KEWL!!

Pun intended!

Thanks for posting back your success! Good to see Positive results..

So now your A FAN of Relays huh?? (OK, enough puns.. )

Happy Crusin'

Doc

[rapsag]

Just thought I would RELAY the results.

[docvette]

Doc here,

Absolutely SHOCKING!

Doc

[rapsag]

That's enough! You're GROUNDED.

[docvette]

Doc here,

I feel like my CONTACT in this thread has been cut SHORT... And headed in a NEGATIVE Direction..However..I do understand your RESISTANCE to my Puns...

Doc

[rapsag]

Doc,
Thanks for the HOT LEAD on wiring. It gets a little CRIMPED under my hood. But I was a good SOLDER and did not complain.
rap