Circuit Breakers

[OverlandMan]

I know one of the circuit breakers is for the cooling fans. What is the other one? And which breaker is which? I looked through my tech service manual and either its not in there or I'm overlooking it somewhere...

The breaker on the right (in the pic below) has no positive (+) 12V or continuity regardless of key on or off. Where is the feed for this circuit coming from? The breaker on the left has 12V (+) on both sides continuously.

I removed the Fanzilla assembly so that is why the fan and fan-fail relays are missing.

* Ignore the crappy hack-job speaker wire in the pic. It will come out eventually.

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[DMC5180]

The left breaker is Cooling Fan (Radiator). It is the +12V feed to the Fan relay. It should be live on both sides with key on. Breakers are just pass thru devices.

The right Breaker Is the Cabin blower fan. It should also be +12V (both sides) with the key ON. It appears the Bottom brown wire has gotten hot ( dark insulation). Check it for corrosion.

[dmc6960]

The left breaker is Cooling Fan (Radiator). It is the +12V feed to the Fan relay. It should be live on both sides with key on. Breakers are just pass thru devices.

The right Breaker Is the Cabin blower fan. It should also be +12V (both sides) with the key ON. It appears the Bottom brown wire has gotten hot ( dark insulation). Check it for corrosion.

Look closer Dennis, I think its the opposite. If you look closely at the right breaker, you'll notice that there is only one in and one out (cooling fan). The left breaker has the multiple (blower/starter mod). The cooling fan one also does NOT use brown wires. One is black with an orange stripe (the one you think got a little toasty). The right breaker (cooling fan) will only have power with the cooling fan relay activated (which is removed in the pic, power goes from the relay, to the breaker, then back to the fain fail socket). The left breaker (blower motor) will have 12V at all times.

Considering these breakers can be interswapped, its easy to misplace them, and one should never be relying on what its "supposed" to be but rather what it really is. These particular breakers MAY have already been replaced at one point, the terminals appeared to be "nutted" on to the breaker threads. If I recall correctly the stock breakers had the terminals riveted on, with no threaded terminal.

[WelmoedJ]

The values of the circuit breakers are:
25A for the 4 wire breaker (interior fan)
40A for the 2 wire breaker (radiator fans)

Contrary to what has been said in another reply, you better not swap them as 25A is too weak for the radiator fans (they draw some 30Amps while working).

[Bitsyncmaster]

25A for the 4 wire breaker (interior fan)


Blower breaker should be a 30 amp. I measured the blower current on speed #4 and it runs 23 amps. (from memory).

[dmc6960]

Contrary to what has been said in another reply, you better not swap them as 25A is too weak for the radiator fans (they draw some 30Amps while working).

No I agree with this, never swap the breaker's function. However do not rely on someone else's picture to identify which one is which for your own setup, the breakers are PHYSICALLY interchangeable in the holders.

[OverlandMan]

It appears the Bottom brown wire has gotten hot ( dark insulation).
Yep - the Fanzilla partially melted.


The right breaker (cooling fan) will only have power with the cooling fan relay activated (which is removed in the pic, power goes from the relay, to the breaker, then back to the fain fail socket). The left breaker (blower motor) will have 12V at all times.


That makes a little more sense then. The actual constant 12V (+) then coming from the battery feeds directly to the relay. The breaker sits between the fan relay and fan-fail relay. Correct? I'm referencing this schematic:

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These particular breakers MAY have already been replaced at one point, the terminals appeared to be "nutted" on to the breaker threads. If I recall correctly the stock breakers had the terminals riveted on, with no threaded terminal.

You are correct. I found a receipt in the glove box dated last year (from PO) that indicates the cooling fan circuit breaker was replaced. Looks to me like both have been replaced.

What would be the issue with replacing the cooling fan circuit breaker with an ATC fuse? 40A according to WelmoedJ.

At some point down the road I'm going to purchase one of Dave's solid-state solutions for both the fan and fan-fail relays. But for the time being, I was planning on running the fans load on one 40A relay with a manual switch as the trigger (So I can at least drive the car to go get some gas :)).

[dmc6960]

That makes a little more sense then. The actual constant 12V (+) then coming from the battery feeds directly to the relay. The breaker sits between the fan relay and fan-fail relay. Correct?

Yes, that is absolutely correct. The fact that your car was previously running fanzilla means that nobody mucked with the wires for the setup, a good thing from a future-improvement standpoint.

Don't do a manual switch for the fans, just trigger it with ignition. Better to have them run all the time than to accidentally forget to turn them on.

[OverlandMan]

Yes, that is absolutely correct. The fact that your car was previously running fanzilla means that nobody mucked with the wires for the setup, a good thing from a future-improvement standpoint.

Don't do a manual switch for the fans, just trigger it with ignition. Better to have them run all the time than to accidentally forget to turn them on.

Yea I thought about that too but didn't want the load of the fans drawing on the battery while starting the engine. I guess I could find a timer or some type of delay... but seeing as my goal is to run Dave's solution, I didn't want to spend a bunch of $$$ & time on a temp solution.

Aside from the switch, do you see an issue swapping the breaker for a fuse (same amp rating of course)?

[dmc6960]

What would be the issue with replacing the cooling fan circuit breaker with an ATC fuse? 40A according to WelmoedJ.

No I wouldn't personally do this. The fans serve a critical enough function that you want the breaker's ability to reset. If something relatively benign blows the fuse, your screwed. If something relatively benign blows the breaker, it'll fix itself.

INDIVIDUALLY fusing the fans on the other hand had its merits, as a single bad fan can overrun the wiring to itself, but still possibly not draw enough power to blow the breaker before damaging the wiring. Also has the possibility for the failure of one to fail the other as well since they run off of a common breaker.

[OverlandMan]

No I wouldn't personally do this. The fans serve a critical enough function that you want the breaker's ability to reset. If something relatively benign blows the fuse, your screwed. If something relatively benign blows the breaker, it'll fix itself.

INDIVIDUALLY fusing the fans on the other hand had its merits, as a single bad fan can overrun the wiring to itself, but still possibly not draw enough power to blow the breaker before damaging the wiring. Also has the possibility for the failure of one to fail the other as well since they run off of a common breaker.

Ah - good point. Fusing both separately might be the way to go until I get my permanent solution. Thanks for the info.

[Chris4099]

One other thing to mention is your relays are original. They were very poor and under rated, so it would be a good idea to purchase a relay upgrade kit to replace them. The kits out there also include new circuit breakers so if yours are also weak and trip too soon, the replacements should fix that.