Finally figured out why my a/c wasn't working... short in the ECU... anybody got a lead on the best place to pick up a used one? There don't seem to be any in the local salvage yards...

Short in the ECU? The ECU is actually covered by a 96 month, 80,000 mile federal emissions control warranty (as are the cats) so you may be able to get it replaced under that coverage.

Brent

How did you determine that the ECU is the cause? Applying direct power to the b/y wire at the ECU terminal and the a/c came on?

Did you bypass each of the safety switches first to see if one of the them was the culprit?

I don't mean to be a dick, but I've never had an ECU be the cause of the a/c not working.

An a/c thermal control amp, high pressure switch, low pressure switch, head unit and even a bad compressor ground have all been culprits. But an ECU would be the first.

If it is, then pm me for sure, and I'll see what one would cost with the XOC discount at work.

My Toyota mechanic said that the wiring coming out of the triple-pressure switch had corroded and grounded together, causing a short in the ECU... supposedly I've now lost a ground that goes to the relay or something like that... now that everything's been repaired (except for the ECU), I'm gonna try and get the ECU replaced under the warranty (thanks Brent)... any other suggestions? I don't know what to do, but I don't see why I should be out of pocket $700 because of some crappy Nissan wiring...

Um.... take it to a Nissan mechanic?

You can't cut out the whole post to make it look like my Toyota guys a moron... he knew what was going on, and told me it was my ECU... FOR FREE... I don't get that kind of service at any Nissan dealers around here... actually, the only Nissan dealer I've spoken to so far said that even if it's not due to water damage (which it's not), and they see that there's been water in my truck, they'll void the warranty and charge me full price for a new computer...

:rolleyes: I didn't mean to make it look like your mechanic was an idiot. I was just pointing out that if you don't know what to do, maybe you could try going to a Nissan mechanic. That's all. I shoulda deleted the "said" part in that quote -- my bad.

I already know what a Nissan mechanic will do... he'll charge me about $200 to tell me my ECU is screwed up and then another $1000 to replace it... thanks, but no thanks...

Or not help at all.

Hey Allen... I'd like to talk to you to see what you think... I'm just really stumped and would like someone else's input on this, specifically someone who does this type of work daily... can I give ya a call?

Sure, you have my #? I'll pm you.

You forgot to put the number in your PM... ... working too hard?

Sorry dude, both my phones are dead. As soon as my cell charges, I'll call you tomorrow/today (whenever you read this). Good luck on your tests!

Ok... pulled the ECU... it had mud in it... glad the only problem is the ac... figured out the problem is indeed in the ECU... my question is, instead of having to replace the entire unit, could I just take this to someone who builds PC boards and replace a resistor or a chip or something? I didn't see any burned spots on the board or anything... could it be that simple?

It's nearly impossible to repair an ECU without a schematic for it. Without one, it needs to be reverse engineered first, which takes a crapload of time.

That was going to be my second question... any way to get hold of a schematic?

It's not in the service manual.
Just get the new ECU, they're really not repairable other than trying to wash 'em out or something.

I'm taking it to the shop tomorrow... the only problem with getting the new ECU is cash... right now I'm broker than broke (2 job changes in a month killed me), but it's still 100 degrees out here...

Since the ECU is already toast, you can turn on your A/C compressor by grounding the ECU pin that is now dead.

That's actually what I've been doing, pretty much... but now I'm trying to get the truck ready to sell, and that's not gonna work anymore...