Electric fan wires getting hot!

[JMD]

Hey all,
I have a Old Air Products dual electric fan and shroud setup on my ‘68 k10. The fans are manufactured by SPAL and I believe they pull 65 amps each. Everything worked perfectly, but I was unhappy with having the relays and fuses bolted to the core support in plain sight. I decided to extend the wires so I could mount everything inside the cab.
The wires, fuses and relays are now getting EXTREMELY hot, so obviously something is wrong. The fuses don’t blow, but instead, they just start to melt and turn brown. The relays are too warm to touch as well after just a couple minutes of run time.
Because the leads coming from the fans are 12ga and only 18” long, I guess I’ll have to mount the relays and fuses right next to the battery, right? Or can I extend those leads with some 10ga or 8ga wire?

[HO455]

It sounds like you are experiencing a low voltage situation. This could be from the wiring being too small for the amp draw and the distance ran. Or it could be from a bad connection(s).
I would check for bad connections first. You can check for bad connections with a voltmeter. If you put one lead of the meter on the positive post of the battery and the other lead on the 12 volt positive lead at one of the fans the reading will show how much voltage is being dropped by the circuit to the fan. If you put one lead on the 12 volt negative lead on a fan and the other lead on the negative post of the battery it will show how much voltage is being dropped by the ground side of the circuit. And then repeat the tests for the other fan.
Both of these readings should be very near zero volts. The fans need to be running when you conduct these tests.
Can you describe, or post a schematic, of exactly how you wired the fans?

[JMD]

Thanks for the reply, I'll get my volt meter out and see what I find. I do have a few unnecessary butt connectors in some wires, so I'll solder those connections instead. I also have the fans grounding to the front cross member, which I realized I had removed, painted, and reinstalled at the same time I lengthened the fan wires. I think part of the problem may be that the fans aren't grounded properly anymore.

Here's a schematic of how the fans are wired.

[HO455]

Checking the ground side is a good idea. You may want to run a heavy ground cable from the main frame ground point to where the fans are grounded. That part of the circuit wiring needs to match the size of the wiring supplying 12 volt positive to the relays. One thing you might also consider is moving the fuses to the wires supplying the 12 volt positive power to the relays. From the drawing the wiring to the relays and the relays are not protected if something should short out on that part of the circuit.
Keep us posted on what you find.

[LS short box]

Some what off topic but I got ask. If the two Spal fans draw 65 amps each unless you have a big amp alternator of at least 130 amps wouldn't the fans drain your battery if the fans ran for an extended period of time like on a long road trip?

[Richard]

If the fans indeed do draw 65a each imo 12g wire is a little light to just one fan. Two fans no way. Also the standard automotive cube relays are typically rated for only 30a. Even the heavy duty ones are only 40a.

[Andy4639]

So you physically moved the relays into the cab right? It sounds like you have to much wire that isn't big enough to handle the load. The relays should really be out by the fans and battery. The main load wire that runs from the battery to the relay and then to the fans should be as short as possible. The trigger wire doesn't matter because it doesn't see as many amps. The amp draw is pretty good on these fans. The shorter the wiring the better. You could make some covers for the relays and hide them inside the core support are under the battery tray. You have several places to do this.

[gmc684x4]

A 65 amp load would need 6 awg or 4 awg wire to move 65 amps
12 awg is good for 20 amps
Too small wire voltage drop
Poor grounds have an effect as well
Do you have a clip on ameter to check actual loads ?

Drastically undersizing the wire can lead up to an electrical fire hazzard

Fans will be on more when stopped at a light parked etc motor gets cooled by air movenent when driving on the highway flowing through the rad

Think of hydralics the reduction in pipe size will increase pressure needed to work ( higher amps) which drops voltage lower

[gmc684x4]

Looking at your dwg each fan should be wired with at leaat 10 awg

[JMD]

So I did the test that “HO455” suggested and I got a 7.5v drop...That seems excessive to say the least.
Maybe the 65 amps per fan is inaccurate. I can’t find any information about the draw from my fans specifically, I just based that number off of a similar 16” SPAL fan.
But come to think of it, a 65 amp draw doesn’t make much sense considering the kit provided 2 standard automotive relays rated for 40amps, and the fuses provided with the kit were both 30s.
I do have a high output alternator rated for 110 amps.

I bought a bunch of 10ga wire to replace the existing 12ga, and I plan to solder all the connections this time.

Or do you think I should just wad the relays and fuses up under the battery tray? That would significantly reduce the wire lengths, but I’m worried about moisture. The truck isn’t supposed to see rain or wet roads, but...$hit happens.

[JMD]

Also, from my understanding since the fans are hard wired from the factory with 12 gauge wire, simply adding on a bigger wire won’t make any difference. The transition from 10 gauge to 12 gauge will always be a pinch point that will cause a voltage drop as well as heat buildup. Is that a correct assumption?

[HO455]

7.5 volts is definitely too much.
If it helps your decision I have had relays for my head lights and fuel pump under the hood of my daily driver Burban for 20k miles with no problems (photo #1) and the PO mounted the compressor control relay to the frame crossmember just behind the fuel tank. (Lord knows how long ago it was but I carry a spare just in case).(Photo #2 blue arrow) But it never rains here in Portland.
I did put a drip cover under the hood to help keep the wiring there dry. (Photo #3)

[HO455]

Originally Posted by JMD

Also, from my understanding since the fans are hard wired from the factory with 12 gauge wire, simply adding on a bigger wire won’t make any difference. The transition from 10 gauge to 12 gauge will always be a pinch point that will cause a voltage drop as well as heat buildup. Is that a correct assumption?

A properly made solder connection should not cause a voltage drop nor will it get hot.

[LS short box]

Twin 16" fans? They will move a ton of air. I've always used Spal 16" single fans on my LS swaps. No AC though. A typical 16" Spal draws about 35 amps on start up and then once its spinning its less. Don't how much less but the start always draws the most amps. Relays "good" ones like Hella are water resistant. The cheap auto store relays not so much. The two Hella relays on my LS swapped Jeep TJ (fuel and fan) have been under the hood for 12 years thru rain and snow with zero failures.
Good luck finding the solution and keep us in the loop.

[Andy4639]

Well as I stated the relays should be as close to the battery and fans as you can get them. My 6.0 LS has head lights, fans and other relays all under the hood and no problems. I haven't had the first one to fail! Tomorrow that will change I'm sure. My headlights are 10+ years old. Ls is 6 years +.

As you stated wad them up and put them under the battery.

[Richard]

Originally Posted by JMD

Also, from my understanding since the fans are hard wired from the factory with 12 gauge wire, simply adding on a bigger wire won’t make any difference. The transition from 10 gauge to 12 gauge will always be a pinch point that will cause a voltage drop as well as heat buildup. Is that a correct assumption?

Not really. A short piece of wire that is to small can act like a fuse if to small. A fuse is basically just a small piece of wire designed to melt at a certain amperage. Running bigger wire to compensate for voltage drop in a longer run is commonly done in AC and DC circuits. What was said earlier about wire size and amps is correct. Though in DC circuits it is common to see smaller gauge fine stranded wire ran than required for AC circuits. Also if 30a fuses were provided with the fans, they do not draw more than that. 10g is fine.

[JMD]

UPDATE:
I spent last weekend stripping all the old wiring out and relocating the relays and fuses right next to the battery. Since the fans and relays all came with 12ga wires I kept them intact and only used 10ga wires to go from the battery to the relays (About 1' of wire total) The fans are fed by about 3' of 12ga wire and are grounded to the front crossmember. All connections are soldered except for the ground and power wires on the fans, which have plugs so they can be easily removed.

In other words, I cut about 30' of wire out of the circuit hoping to cut down on voltage drop.

It didn't work. I ran one fan last night for about 5 minutes and the wires were too hot to touch. The relay was also hot enough that the plastic housing was starting to deform. I haven't been able to put a volt meter on anything to see what the voltage drop is, but I'm guessing nothing has changed.

So what now?

[HO455]

Can you post some pictures?

[Richard]

Originally Posted by JMD

UPDATE:
I spent last weekend stripping all the old wiring out and relocating the relays and fuses right next to the battery. Since the fans and relays all came with 12ga wires I kept them intact and only used 10ga wires to go from the battery to the relays (About 1' of wire total) The fans are fed by about 3' of 12ga wire and are grounded to the front crossmember. All connections are soldered except for the ground and power wires on the fans, which have plugs so they can be easily removed.

In other words, I cut about 30' of wire out of the circuit hoping to cut down on voltage drop.

It didn't work. I ran one fan last night for about 5 minutes and the wires were too hot to touch. The relay was also hot enough that the plastic housing was starting to deform. I haven't been able to put a volt meter on anything to see what the voltage drop is, but I'm guessing nothing has changed.

So what now?

Maybe cheap relays? Running 10g would not have hurt anything. You stated that fan ground is to chassis. Check battery grounds to body, chassis and engine. Was the engine running while testing fan? If not the voltage from battery may have dropped after a time causing a higher current draw. Battery is mainly for starting vehicle. Vehicle is powered by the alternator once it is running.

[franken]

If the wiring and relay are getting too hot, there's too much current flowing through them. It's that simple.
Is the motor also hot? Motors do get pretty warm so it could be hard to say if it's too hot. I'd get specific info on the fan motors and their current rating.
On the 7.5V reading, I'd guess the OP is measuring voltage across the fan, not just the wire.

[gmc684x4]

Disconect power to the relay for fan turn relay on check with a good ohm meter for resistance across the power to fan contact reading should be much less an 1 ohm example 0.2 ohm would a good reading

The relays could have been beaten up to much already

[LS short box]

If I had this problem and after trying the fixes that you have I would take the fans off along with the wiring and relays. Then find a electric shop the that can bench test it and give advice on the fix. They can measure amp draw and resistance accurately. We happen to have a great shop that rebuilds starters and such which could trouble shoot this in about 10 minutes.