Help with electric fans
 

I have a 4.8 installed with dual electric fans, the PCM was programmed to turn the fans at different temperatures. Here is my problem, every time the fan #1 turn on, it burn the fuse it has a 30 amp fuse, when fan #2 turns on, the same happens. So I start looking for info to make sure the relays were wired properly, I think they were, I follow Brendan info. The relay that I have had the 87 wired into the 30 amp fuse and the 30 into the + cooling fan, so I switch them just like Brendan has them, the relay 30 going into the 30 amp and the relay 87 going into the + cooling fan. Why will it keep burning the fuses, I use a test light and with the engine off, key on, I test the relay #30 and I got light, since is coming from the fuse, then I test the 86 and I got light, I test the 85 and I got light, I tought 85 was supposed to be ground from PCM, does any one knows what is going on. I was supposed to take my truck to a parade but I guess that is cancel until I find out the problem. By the way I never notice the problem because I dont use the truck that much, and when I use it is always on the highway. Thanks for your help

30 = fused power.
87 = to fan.
85 = 12v for relay coil.
86 = pcm to ground.
If you are trying to run both fans off 1 relay, that relay may be fried.

If 86 is hot and the pcm is not calling for fans, there's a problem...

Another thing to look at is making sure you get a full 12V to the fans when running. Electric motors actually draw more current if the supply voltage is low. So make sure you have the right gauge wire, good solid clean connections, good ground path and that you wired the supply into the right spot.

You could also have a short somewhere. Maybe the relay is fried or one of the fans is shorted. Try unplugging the fan and replacing it with a light bulb. If that blows the fuse when the PCM turns it on then start rewiring things.

look out for 87A as well. thats hot with relay off.

I thought I fixed the problem this morning, but I was wrong. Before the engine swap I had a ford 390 engine inthe truck and I was running the fans using a Dakota Digital, but I was using a 40 amp breaker, so this morning I wire the fans using the same 40 amps brakers, I am running two relays, one for each fan. The first fan turn on at the set temperature, so had about 2 1/2 to drive 100 miles to be in a parade with my truck, thinking the fans were good, I left, no problems in the highway, when I was in the parade since we were moving slow, the temperature went up, and the fan #1 went on, so temperature drop, but when the temperature went up again, this time the fan #1 did not turn on, so temperature keep climbing and fan #2 turn on, so temperature drop again, but when the temperature start going up again, this time none of the fans turn on, and temperature climbing, so I had to leave the parade to cool the engine. What seems to be the problem, is it normal for the relays and breaker to get hot, and if they get hot, do they still work. Another question, when the PCM is not sending the signal to turn the fans on, what is 86 doing, is it +

Thanks for all your help

what kind of fans do you have? Some "big" OEM fans will have a big current in-rush higher that operating amperage.

Isn't that the way is should be? With 12V on the other side of the coil relay you have 12V sitting there waiting for the ground to turn on the relay?

The fans I have are from a chevy tahoe, dont remeber if it is a 02 or 04 chevy, but are from a chevy SUV. So you have 12v in the 86, when the PCM opens it sends the ground and activate the relay, so the wiring is fine, but then, how come sometimes the fans go on, and sometimes they dont.
Thanks

Correct. It should be hot on an LS1 swap since the PCM pulls 85 to ground activating the relay.

Did you make your own relay plug? You may have a loose female spade. I had this problem on my old setup with a relay controlling my coils. The wire was barely in the spade connector after I had pulled the plug off a few times. The car would run only run intermittently.

Thanks for all the info. No, I did not make my own plugs. On Sunday afternoon I add power to the relay and the 85 wire I ground it and the fan turn on, so they do work, I just need to make sure I wired them correctly. Question, do the breakers stop working when they hot and they reset again when they cool, or they only stop when they see an overload.

Thanks again

Do you have manually resetting circuit breakers instead of fuses? If so, then yes, they'll pop if they get too hot. That is how they pop to begin with (same with fuses).

the breakers are those self resetting breaker (40 amps) that you can get from any auto parts store, and I check when I when this happens and they were hot. Will it be better to use a 40 amp fuse instead of the breakers, or do I need to go to a 50 amp, I dont know what kind of fuse these truck with electric fans came with.

Thanks

If the truck fans are anything like the Mark VIII or Taurus fans then they pull a boat load of amps, especially at startup. For instance, it's reported that the Mark VIII fan can pull 100 amps at startup with a continuous draw of 42 amps.

If you are tripping the breaker, then the breaker could be undersized for the draw. A fuse would not help here either as it would pop. I've searched for a few minutes and did not run across anything that discusses the stock Tahoe e-fan amperage draw. You could always increase the breaker to 50 amps, but I generally do not recommend simply increasing a fail safe break point without understanding what is causing it to trip.

yep..
 

my bad....4 some reason, I was thinking the test was with the key off...Gettin' too old.. CRS is setting in!:nod:

As suggested..
 

find the problem.
Stacking a bigger fuse in will eventually out run the wire size, then the wires will become your fuse...

Not sure about the truck fans, but F bodies use a 40 amp maxi fuse on the constant side.of the relays to the fans, I would think the trucks would be similar.