Cooling fan relay and fuse block melted. Need help.

[billtherealtor]

First you guys will have to forgive me becuase I do not know much about cars. So I am typing from what my friend tried to fix my car last night and we are lost.
I noticed that my car would get hot while sitting in traffic but fine on the roads. About last summer time So I checked the relays and found r20 (engine cooling) #3 to be melted and the fuse block is melted as well. We thought maybe a bad relay and replaced it. After doing a cam swap the problem has now come back and just destroys the relay in a few hours. I have checked the wiring harness the go to both fans and they look fine. We ran power using a power probe and they both work on low speed but when jumping the relay in R20 location it goes up 26 volts and stops the power prob. and only one fan works on high speed. I ordered a new fan motor which is on its way but I am thinking something maybe under the fuse block is bad or there is a bad wire somewhere.

I found online Painless Performance LSx Dual Fan Relay Kits thinking maybe I can bypass the whole thing but dont know if that will work since the fans work on dual speed. Or maybe just aftermarket cooling fans all together. I am open to any ideas and I hope you I didnt confuse anyone since I am trying to understand how all this works. Thank you in advance for any help.

[Greg@PacePerformance]

We had a customer send back an LS3 controller harness and the fan relay and socket looked just like yours. I was thinking the customer used too large of a fan that was drawing too many amps, but after seeing yours look exactly the same with stock fans I'm not sure now.

Sorry I don't have an answer for you, but I have seen that happen before.

[billtherealtor]

We had a customer send back an LS3 controller harness and the fan relay and socket looked just like yours. I was thinking the customer used too large of a fan that was drawing too many amps, but after seeing yours look exactly the same with stock fans I'm not sure now.

Sorry I don't have an answer for you, but I have seen that happen before.

Thanks Greg I guess I am going to start by replacing the fan motor. I found a used fuse block on ebay as well.

[Greg@PacePerformance]

My next guess is that terminal is not crimped very well and is creating tons of heat from the resistance.

[THE Adam V]

If only one fan was running there you go. The module is commanding both fans on but only 1 works. Therefore causing that fan to work twice as hard. The increasing temps from the cam swap probably made things even worse. Replace fan assembly and fuse box and go from there. There's not much more to go wrong

[STL_G8GT]

From Alldata...

The engine cooling fan system consists of 2 electrical cooling fans and 3 fan relays. The relays are arranged in a series parallel (S/P) configuration that allows the engine control module (ECM) to operate both fans together at low or high speeds, depending on cooling requirements. The cooling fans and fan relays receive battery positive voltage from the underhood fuse block. The ground path is provided at G104.

During low speed operation, the ECM supplies the ground path for the low speed fan 1 relay through the fan 1 relay or low speed control circuit. This energizes the low speed fan relay coil, closes the relay contacts, and supplies battery positive voltage from the FAN 1 fuse through the cooling fan motor supply voltage circuit to the right cooling fan. The ground path for the right cooling fan is through the cooling fan 2 relay and the left cooling fan. The result is a series circuit with both fans running at low speed.

During high speed operation the ECM supplies the ground path for the fan 1 relay through the fan 1 relay low speed control circuit. The ECM supplies a ground path for the high speed fan 3 relay and the fan 2 relay through the fan 2 relay or high speed control circuit. This energizes the fan 2 relay coil, closes the relay contacts, and provides a ground path for the right cooling fan. At the same time, the fan 3 relay coil is energized closing the relay contacts, and provides battery positive voltage from the FAN 2 fuse on the cooling fan motor supply voltage circuit, to the left cooling fan. During high speed fan operation, both engine cooling fans have their own ground path. The result is a parallel circuit with both fans running at high speed.

Fan schematic.pdf

[STL_G8GT]

Bill, it makes sense that only one fan works on high speed, since that fan still has a complete circuit to ground independent of the other fan. At low speeds, both fans are in series and each runs half as fast. When in high speed mode, each has its own ground path and they operate independently at full speed.

I'm not sure what you mean when you say it stops the probe? Or even exactly what you mean when you say probe... do you mean jumper?

Basically what happens is the car says ok we need low fans, and relay #1 fires up and sends power to both fans in one chain, and they share the power (run at half speed basically). When the car says we need full speed fans, there is a relay (#2) that gets a signal from the ecm for high speed, and now fan one you have your own ground path and leaves fan #2 to figure out its own ground path. Luckily, at the same time, the fan #3 relay gets it's own "trigger" or "go" signal from the ecm, and gives fan #2 its own dedicated ground. Both fans run at full speed.

Your issue is that both run at low speeds, but then only one will run at full speed. That makes me think that the fan motors are ok, since the signal goes through each motor when in low speed. Of course fan #2 won't fire at full speed, because your relay #3 is completely wonkers. I saw that the terminal #87 is the one that's burned up - and that terminal is the one that is on the fan side of that relay... which makes me think the problem is originating AFTER the relay.

Then again, remember that relay #2 and #3 are connected... and if relay #2 doesn't do it's job, but relay #3 does, you have a direct shot from relay #1 through the fan, through relay #2 to 12v coming out of relay #3 - which could be bad...

I would remove relay #2, and figure out what car condition would command high speed fans (maybe A/C on?) - and make sure then that pin 85 on the plug for relay #2 switches to 0 resistance to ground. This indicates that the ECM is commanding high speed fans and that the signal from the ECM is correct. Once you know that relay #2 is getting signal, then you need to make sure it's good... put a new one in there. I know you said that the fan came on high speed, but I can't tell if you were ever able to get the car to do it, or if it was only when you "probed" it, whatever that means.

Now that you're sure that relay #2 is doing it's job, and the ecm is commanding that relay to come on under a high speed fan need situation, you've isolated the issue to relay #3, the fuse box, the wiring, or the fan. Chances are the relay isn't bad, you've changed it a few times now I think. From a wiring standpoint, you have checked the wires yourself... and if you say they're good, well... That leaves the fuse box or the fan. If the fans ran on low speed, I would be inclined to think they're fine. Finally, the fuse box - short down in there or like greg said a poorly connected terminal could be your problem.

In no way am I promising that this will be the fix to your issue, but it's the way that I would tackle it.

Lastly- anytime I see neons, etc, on a car, I immediately think wiring nightmare. This is NOT an indictment on you in any way, but if this came back as connected in some way to rewiring or modified wiring under the hood, I wouldn't be surprised.

[billtherealtor]

Thank you for all the info and help. This is the reason I am glad that there is still these forums around and people willing to provide their help. I am meeting with a friend today to run more test and take out the whole cooling fan assemble and also checking all the wires. I already have a new fan motor here and I was able to find a use Fuse block for $115 that should be here on Tuesday or Wednesday. I will make sure I post what we find in case this ever happens to anyone else.

[STL_G8GT]

Thank you for all the info and help. This is the reason I am glad that there is still these forums around and people willing to provide their help. I am meeting with a friend today to run more test and take out the whole cooling fan assemble and also checking all the wires. I already have a new fan motor here and I was able to find a use Fuse block for $115 that should be here on Tuesday or Wednesday. I will make sure I post what we find in case this ever happens to anyone else.

No sweat, good luck!

[avalonandl]

A fan motor whose bearings are shot will draw more current. I think you are on the right track replacing the fan motor. I had to replace fuses on my GTO.

Avalon