Any suggestions on this FUSE blowing issue?

1999 Tacoma 3.4L

Recently bought. NO history. No apparent freon leaks.

AC fuse blows every time I press the AC button. This is with the fan blowing. FUSE also blows with the compressor unplugged suggesting there is a short somewhere.

I bought a short circuit finder and hooked it up to the AC FUSE. I have continuity between the AC button, FUSE and compressor plug connector when the AC button is off.

When I press the button, I lose all continuity. Even with the short finder attached at the AC FUSE, when the AC button is pressed, there is nothing. Makes me wonder something is going on between switch and FUSE?

The switch is brand new.

I've visually looked at all the wires and they all appear good.

I'm totally confused.

Ideas?

 

You need a wiring diagram along with a multimeter or short finder to effectively find the short. There's a relay involved and other parts, so it makes it hard to make sense of your short finder results. The AC compressor motor probably has a low resistance, so it could show up as a short, but once it's running and turning it draws less current.

 

Using a wire and a fuse holder, energize the AC clutch with battery power via your inline fuse. If it blows that fuse, you know there is a short in the clutch, if not start working upstream. I have the 99 electrical diagram and can look at that when I get back at a computer and give you some more ideas

 

That would be great.

Just so I'm clear on your suggestion, run a wire from the AC FUSE positive to the compressor, with an inline fuse between the AC FUSE positive and the compressor? See if that activates the compressor?

 

I have a short finder and a multimeter.

Also, since the FUSE is still blowing after unplugging the compressor, wouldn't that lead us to believe it's not the AC clutch? By all means I'll try your idea, but I thought that was the purpose of removing the AC plug?

 

10-4 missed that detail. Yeah start working your way back, last page of this file has the entire A/C circuit:

http://chung.dangkiem.com/VR-Tools/TSKT/VIN_TOYOTA/TACOMA/Wiring%20Diagrams/Overall%20Wiring%20Diagram.pdf

 

Thanks for the diagram. Is it best to work back from clutch or from AC switch?

 

I would divide and conquer… split things up in the middle and then see what you find, checking for short to ground as you go

 

If the fuse blows only when the A/C switch is on- I would disconnect the a/c amplifier, then try it. If it doesn’t blow, look downstream of ac amplifier ( and try engaging the clutch using a test lead plus fuse as I said above, but inject the current at the ac amplifier terminal/connector (with the amplifier removed)).
Note you could also have a bad amplifier, hard to troubleshoot that without a replacement module on hand.

 

Just my $0.02

Reviewing drawing #33, and provided that one of the devices have shorted and not the wiring itself, there are only 3 devices that have grounds. 1 - the AC Clutch. 2 - The AC Amplifier. And 3 - the switch itself.

OP mentioned that there is a New Switch in service. Was the switch replaced before or after the fuse started blowing?

 

Good stuff with your observations.

The AC never worked. Never dove deep enough into to know the symptoms.

My son bought the truck and he said the AC didn't work. Now, 6 months later and living in Phoenix, we need it running. LOL

The switch in the truck was broke. The front crack and you could see the light bulb inside. I'm pretty sure the compressor never came on.

I bought a cheapy off the internet last week for like $12. Fits great. As an LED instead of a bulb. Obviously not OEM. With the headlights on, the backlight to the switch comes on, but the main GREEN light won't come on when you press it. The fuse blows. Even with a new fuse, when you push the button, you don't see the GREEN light come on for split sec....

I read on Amazon the reviews. Mixed. Several said the switch didn't work even though it falls into the parameters of the Gen 1. I'm wondering if this switch is faulty?? I'm thinking about buying an OEM which is way more expensive, but could the switch be the problem?

Like I mentioned before, with the compressor unplugged and the AC switch off, my short finder gives a tone at the AC fuse, the AC switch and at the compressor plug. That would tell me without pressing the button, I have full continuity throughout. But again, when the switch is pressed, the fuse blows and I have no tone anywhere with the short finder....

 

Best to find the problem before buying the parts.

I'm just armchair troubleshooting. But something isn't right here. You should not have continuity with the switch OFF else the AC would be ON all the time.

I would run with @MikeWH sugestion by checking the clutch with a jumper wire (and a fuse). 2nd, unplug the amplifier and turn the switch ON.

 

@Jimmyh

@caribe makaira

 

I appreciate any suggestions. I agree not to throw parts at it, but knowing the switch face was broke, exposing the bulb, for $15, I figured I'd replace it....

Regarding the jumper cable, I will try that tomorrow and report back.

The continuity thing is backwards! I don't understand it. That's why I was wondering this cheap switch is faulty? But what really makes this situation odd, is when the button is pressed and the continuity is stops throughout, the fuse blows....

I need to find where the amplifier is. I have the dash and control panel disassembled now.

 

Since the switch wiring does have a ground, possible that the switch could be wired incorrectly or faulty. It is still preferred to isolate the problem before buying parts.

The weird continuity problem could indicate the possibility of a bad amplifier. Once again "The proof is in the pudding"

The clutch is well know for causing this problem on any vehicle. And is the easiest to eliminate with a jumper wire.

 

Yes, agreed. The clutch seems to be the culprit for many, but how does that fall into this equation if all my continuity tests are done with the clutch/compressor unplugged?

 

Depending on how you ran the tests, and from the information provided, your just telling me that you have a "closed circuit" but not a FAULT. The amplifier could be telling the compressor to START?

Your testing to much of the circuit at one time to provide any usable information.

 

Interesting...Ok. I will do the jump test tomorrow.

I'm assuming I just cram the jumper wire into the plug hole on the compressor? Would I run the positive with the fuse off the battery or the positive side of the AC fuse that's blowing?

 

Preferably - unplug the clutch, run a jumper from the (-) terminal of the clutch to ground. Run a (+) form the battery (with a fuse) to the (+) terminal of the clutch and just touch it.

 

Ok I will try that. When I unplugged the clutch, I noticed a nut and wire next to it. I assume that's the ground on the compressor? I didn't mess with it since it's in an area I can hardly access. If that's the ground, can I just leave it be and simply touch the positive? Or actually jump that nut to another ground source - Assuming it's a ground.