Fixed: Turning on the AC blows IG1 #2 fuse

I’ve read through all the other AC threads but still looking for help with my 2005 Tacoma which blows the IG1 #2 fuse with the AC button pressed.

Heat works fine and blows on all speeds. So this rules out a blower issue.

What I’ve tried:

1
With the MG CLT relay pulled I blow no fuses. Tried swapping with horn relay and still blows fuse.

2
Unplugged positive wire at the clutch to test voltage, blew fuse since it completed the circuit.

3
Clutch spins freely by hand. Connected clutch to battery positive directly and clutch engaged.

These tests lead me to think the clutch is fine, but the wiring may be the issue. Where do I start in testing the wiring?

Only mods to truck wiring are a Gentex rearview mirror connected in headliner and a backup camera connected to reverse lights. Since the fuse only blows with the MG CLT relay connected, I wouldn’t think these would be an issue.

It seems I should test connections to the AC lock and AC Amplifier. How do I do that?

Anything else this could be?

Thanks for your help and suggestions.

 

I would venture to say that you you have already isolated it to the wiring harness between the MG clutch relay and the clutch coil ( Violet Wire ).

 

I agree.

To be sure it's the clutch circuit.
Unplug the compressor.
Test light from battery + (positive) to the fuse terminal. (feed side to compressor)
I like to use the blown fuse, as it keeps you from having to cram test leads down in the terminals.
Most fuses have bare spots on top to check each side of the fuse.

If the test light lights up, you have a short to ground.
If not......You have more diag to do.

FWIW, here is the locations of EA1 and the pinout.
Something tells me you'll be there next.
You'll be looking for pin 3 (violet) wire.

 

To be clear, nothing else is between the violet wire leaving the relay box and the clutch, right? So I would need to inspect it for fraying or damage? It is of course in a tube of a bunch wires. Anyway to just bypass it?

 

There is a connector, EA1, between the fuse box and the compressor.

 

Yes, I’ve seen that violet cable. Just wondering if their is an easy way to temporarily bypass the EA1 connections from the relay to confirm the fuse doesn’t blow with the AC on?

Could I somehow connect a wire from the MG CLT relay directly down to the clutch to test before cutting the violet wire? Or is their an easy way to pull the violet wire from EA1 to replace it?

 

Well yes you could run a new wire from the MG CLT Relay to the MG Clutch Coil to bypass the connector and OEM Purple Wire. I would do it as a temporary check first before cutting out anything.

 

Thanks for confirming. Just trying to make sure I’m going to do this correctly: I should be able to run a wire directly from the #5 socket terminal with the relay pulled to the clutch. Ignoring #3 since that feeds the violet wire. Do I need to do anything with socket #1 or 2 for this test?

 

Try not to touch pins 2 or 3.
Good luck. Your test is sketchy.


I do have one question.
What the plan for running the new wire?
As in, how do you plan to fix your issue?

At some point, you're going to need to find out where the short is.

 

I don’t have experience with this, so do you have a less sketchy option?

Also, I haven’t replaced any car wires in the past, any suggestions on replacing the violet wire if that confirms as the issue?

 

I mean yeah. You can by-pass it.
But I'd unplug AE1 and see if the fuse still blows.
If not, snip the wire just after the EA1 and just before the compressor connector.
Splice in a new wire.

But what's to say that other wires in the bundle aren't going to rub through at some point?
Something is causing the short.

I'd still like to see what a test light does with the compressor unplugged and test light to terminal 2 of the relay.
Test light to battery +, probe terminal 2 of MGT relay. Compressor UNPLUGGED.

No need to snip wires unless we are 100% sure.

And for others reading. Yes, by-passing is not "right".
But it will work.

 

With compressor and EA1 unplugged, engine won’t start. In ACC mode fuse doesn’t blow.

I did see a piece of metal wire sticking out of the wiring bundle as it runs against the main negative in the relay box. I wrapped a ton of layers an think the fraying was only on the external tape and not penetrating further. The wires are discolored under there, is this from tape or heat possibly?





Once I exposed the violet wire and cleared it from everything I tested and blew my last fuse for the night. So I’ll get back to this testing tomorrow.

I don’t have a test light but have a multimeter. From battery + to relay terminal #2 I get 12.21 volts, .62 ohms in acc, .51 ohms in ACC with ac on.

One thing I discovered is that I left the compressor unplugged and it still blows the fuse. Not sure if that changes anything.

 

With the compressor unplugged, and the EA1 unplugged.
Take your voltage meter and place the red lead to battery +.
Then touch the - lead of the meter to the pin of violet wire of connector.
If it shows more than .5v we have a short to ground.
Be careful, don’t jam the lead too far down into the connector.
That can cause the pin open up and become loose when you plug it back in.
Just enough to touch the wire terminal end.
You can use a needle put in the pin, then touch the needle.
BTW, using a test light saves fuses.
That’s why I suggest using one.

 

When I test the violet pin to battery + I get full 12.2 volts. When I use ohms I get OL. Does this confirm the Violet wire is shorting, needs replacement?

 

If the compressor was unplugged, and you had 12v on the violet wire, yes.
Yes, that indicates a short.

 

Yes, compressor was unplugged for the test! Now to work on rewiring the violet wire.

Thanks for all your help TnShooter and Jimmyh.

 

As I was contemplating my rewire plan I noticed the supply wire to the clutch is orange, not violet. I also see another connector that could be the transfer from violet wire to orange wire. Anything that could be wrong with this connector to cause the short? Any testing possibility with it?





FYI: picked up a test light today!

 

Adding on, looks like it’s a cooler bracket, part number: 88688-04251. Ultimately, if I could isolate the short to this section and replace the whole section I’d be better off or at least it would make it easier to splice in my new wire.

If I can disconnect both ends of the plug how can I test for a short?

Looks like one bolt holds it in place so will attempt to remove that 20 year old bolt next.

Found a photo of it attached to a new compressor.

 

Clip the test light to battery +.
The tough the tip of the test light to the wire. If the light glows. You have a short.
With the test light still touching the wire, start wiggling and tugging on the wire. If the test light goes out. You are close the short. Start looking for bad spots in the wire.

You’ll have to come up with a way to keep the test light touching the wire while you work.

I usually just use a spare piece of wire stuck into then connector. Then an alligator clip on the other end, clip to the test light.

Or you can even wrap the wire around the test light.

 

Dm93 has a good thread on testing here.
https://www.tacomaworld.com/threads/2nd-gen-information-diagnostics.784008/#post-28042153