AC Compressor help!

[reegler]

Did a quick search for my problem and couldn't find anything.

On my 93 1.6L mx3, I just replaced my AC compressor and I thought it was going to fix my AC problem but then I realized that the clutch wasn't engaging so I checked the lead coming from the compressor and there was no voltage when the AC button is on or off. So then it must be the relay or so I thought. But the four leads going into the relay where the compressor was are all connected to ground essentially except for when the AC button is depressed in which case one is not (this lead is connected to another relay) and this is bugging the crap out of me. I might just go to the dealership and get new relays because I just can't figure out what is wrong.

Any ideas? I'm sorry it's not really clear what the problem is....

[umcamara]

Relays don't often wear out. I'd check the Body Electrical Troubleshooting manual in the online manual. It gives a step-by-step procedure for diagnosing problems. It's for a '95, but will probably relate very well.

[SuperK]

check at the relays in the corner of the engine compartment, make sure the ground is connected...

... then follow the wire, make sure it's connected to the AC compressor, to the fan, then to the fuse box.

[umcamara]

No!! Listen to me!

[reegler]

The relays are fine, I tested them out. The voltages going into the first relay (closest to the windshield) are strange. In fact, there are no voltages at all which could explain why it doesn't work when plugged in. The second relay works fine when I press the AC button, it turns the condenser fan on and breaks the ground connection going back to the first relay. I don't understand how the compressor clutch is suppose to get power. I also don't know what the voltages are suppose to be coming out of the power block (the three wires near the two relays, two blue and one black). Before I push the AC button, the voltages are all 12-13V (B+) and when I push the button, two drop to 1.5-3V.

I bought this car two years ago and the two relays are aftermarket (the mazda dealership said so) so those could be the issue if they're not correct.

[reegler]

Ok, So I went back out and followed the wires around and realized I didn't even have a fuse in AD FAN slot. But as soon as I put the fuse in (battery connected, ignition off, acc off) it blew. So then I took out the FAN relay (the six lead relay with diodes) and it didn't blow again. Like I said before, the fuse is aftermarket and came with the car so I'm not even sure if it's right or is working correctly. Something in the relay must be shorting out the 12v line coming from the fuse. So I might just find a junkyard near me and try to find that relay. Or it's the wiring.... who knows.... I'm so confused

[reegler]

I figured it out. It turns out there was a diode in the 6 lead relay that was shorting out the 12v fused line to ground thus why the fuse blew when that relay was attached. Whipped out my soldering gun and detached the diode and everything works wonderfully now! Thanks!

[umcamara]

That diode was probably there for a reason...

[reegler]

If it were the original relay from mazda then I would say the same thing but since it's aftermarket I'm more skeptical.

[umcamara]

Maybe the diode was bad and was allowing current feedback in the direction that it was there to prevent.
You could try soldering in a known good diode of the same spec, or find the mazda relay at an autowrecker.