Today was the first day I have put both fans "to the test". 95* degrees today and had the A/C going the whole time.

Background:

• FAL 292 fans, using 2-relay wiring, one relay for each fan - pretty simple. Both relays are wired up the same way as far as the constant power to the fan, with fuse, circuit.
• Fan 1 runs off PCM for temp control - has performed flawlessly since installation (end of October)
• Fan 2 is running off of the A/C compressor clutch circuit

Scenario:
Fan 2 fuse blew sometime on the way home tonight. I noticed the trans temp started climbing to 180*, which is out of the ordinary - it actually reach 195. Irony: after I shut off the A/C, everything cooled back down, except for me.

Question:
Why did the fuse blow? As far as I can tell, there should be no more amp load on the relay 2 fuse than on the relay 1 fuse. What could have caused the amp spike? I only am using a 20A fuse because 30A is too large for a 12AWG wire (I don't want to start any fires, ya know).

Here is the wiring diagram for Fan 2 relay

 

My best guess would be one of 2 things,
First, I noticed that the hot lead through the relay for fan #2 also feeds relay #1. When ever a branch is added to a parallel circuit, current for the entire circuit increases, as resistance in that circuit decreases. You might want to consider splitting those 2 into different power sources.
Second guess would be that maybe since fan #2 has been working harder due to the a/c compressor running more, that it may have either loaded the circuit or shorted internally, causing the fuse to blow.

Those are the first 2 things that jump off of the top of my head...hope it helps.

 

That 20 amp fuse has nothing to do with the AC clutch relay. The wire coming from that ciscuit is somewhat minimal as far as amperage goes.

Check the fan, make sure it isn't burnt up. Have you tried another fuse yet?

The AC condensor generates a pretty significant amount of heat, that's what caused the temps to raise.

 

I thought that he said that fan 2 runs off of the compressor clutch circuit...(kinda tough to see that schem on my screen too...just clicked it, didn't save it)

 

Yup, you need to check out the fan motor. Is there anything that could have locked the blade up and stopped the motor? The wiring looks fine and 20A for a single fan motor should suffice. When the fan is operating is there a good 12 volts at the fuse? I.E. is there significant voltage drop in that circuit?

 

The relay is switched from the AC circuit, but the current required to switch the relay is somewhat minimal. It's not enough to account for anyhting.

You have to look at a relay as 2 different circuits. There's a switching part, and then there's the switched part. Draw a line through the center of the relay and that will show you the 2 different sides of it.

 

20A is WAY more than enough. I agree that you need to check the fan motor.

 

I put another fuse in and I'm sure it will blow tomorrow (if the fan is still working). I was thinking earlier that there must have been a short somewhere. I didn't think about the fan motor, though (doh!)

I'll pull the fans out tomorrow night and check the fan motor. I think I'll also check the wires coming off the fan motor to make sure there hasn't been any type of wire insulation breach.

Guess I'll ride without A/C tomorrow. Oh well, it's only hot coming home.

 

Well, I had time tonight to pull the fans out and check everything. I can not find anything wrong. I cannot find any wiring problems whatsoever.

I put a new fuse in, turned the a/c on high and let it run. Fan2 ran constantly (as expected) and I ran it long enough for Fan1 to cycle twice - No problems that I can see.

Yesterday, I ran the a/c all the way home from work. I would say that the fuse blew after about 45-50 minutes of run time (based on when I noticed the tran temp rising).

I'm no electrician, but would there be a problem with the fan running that long continuously? Now, I know that Fan1 has never run that long without switching off, so I have no base of reference.

I'm going to go about business as usual and see if it blows again.

 

A couple of things to consider...
1. did you use the fuse/holder from FAL...it was faulty and should not be used.
2. is the wire for fan 2 run near any hot parts...as temp rises, resistance goes up and volt drop is more pronounced, and when voltage drops amp quickly go up. So try moving wires and put in loom.
3. Why not use the fan controller from FAL to controll them?
4. include more of the wiring diagram...does the fuse popping cause both fans to stop?
5. of course dbl check all connections to be sure they are tight (for example the spade connectors that connect to the bottom of the relay sometimes are loose from the factory).
Good luck.
Damon
BTW the FAL fan controller also has a connection for a switch to manually turn them on or off (nice feature) and only needs 1 30amp connection.