What's wrong with my AC?

Yesterday I turned on the AC and within a couple of seconds it blew the fuse. So I replaced it with an el-cheapo fuse this morning. This afternoon, I turned the AC on Bi-level and it seemed to work fine (just not very cold air). I had it like this for maybe 10 minutes, then switched over to the Normal setting. About a minute later, my AC starts blowing a lot less air (but still blowing some). I looked down at my gauges, and saw my battery gauge falling into the red area. I immediately shut off the AC, and I returned to a normal 14 volts. Tried turning the AC on again, and I got the same results. I haven't tried it with the heater yet though.

Any ideas on what might be the problem?

'90 XJ 4.0 w/ AW4 tranny


Thanks

I´d make sure the fuse I used as a replacement isn´t any bigger than stock (think it´s 25 amp). Then unplug (single connector/wire runs to the front of compressor) the clutch, on the compressor, try a QUICK test, see if the voltage drops again when you turn on the A/C (just for a moment). If your still geting low voltage, I´d try the blower on low and high, if the resistor for the blower motor is shorting, the speed probably won´t change with the setting, until you get to high. I think high fan, bypasses the resistor.
Probably either the clutch, blower motor or blower motor resistor. Possibly in the wiring. Got to be careful, don´t want to smoke the wiring or your alternator. 25 amps is pretty hefty current.
If your 90 is the same as my 88, the blower fuse and the fuse for the compressor clutch are the same fuse.
Seem to remember, years ago, a wire in the blower motor resistor burnt through and was shorting across a couple of different poles on the resistor, caused the fuse to blow. Have heard of compressor clutches shorting out. I´ve been lucky with the blower motors so far, but any motor is subject to overheat and short a winding.
Not a solution, just a few places to look.

This wouldn't have anything to do with the fan override switch you put in would it? If you did do it.

8700xjs

8700XJS said:

This wouldn't have anything to do with the fan override switch you put in would it? If you did do it.

8700xjs

Click to expand...

Nope, the fan is wired to a relay I put in, and the relay to the switch. There is no longer any relation between these two.

The AC was working until the other day, and the aux fan still works great.

I inspected my el-cheapo Bronco brand fuse, and it was a 25 amper, just like it should be. The only thing is, the plastic surrounding the prongs is melted!!! Rather than blowing the fuse, it just melted some of the plastic. Talk about a POS!! I put in a quality, USA made fuse, and it blows as soon as the AC is turned on.

I think I am pretty lucky nothing caught on fire. I guess you get what you pay for, but STAY AWAY FROM CHEAP FUSES!!

I just unplugged the AC fan clutch control switch, and it no longer blows fuses, but of course doesn't blow cool air. Is this the culprit? I have a new switch, but I don't think I can change it without draining the R12, is this correct?

The best approach, is what I call divide and find. I can´t picture the A/C fan clutch control switch, you mentioned. My approach would be to figure out, if it´s the magnetic clutch (pully and clutch on the front of the compressor) or the inside fan and/or wiring.
You can isolate the clutch, at the single wire plug, very near the compressor, or just remove the A/C relay (four relay block on left front inner fender, usually the front relay, but not always). If the fuse holds, this will tell you, it´s probably the magnetic clutch or the wiring after the relay.

There are two places that you need to check. One is the blower switch connector and the other is the resistor pack connector. My blower switch fried, smoke and all, and this is what I had to fix. Took me a while but everythings working again.





This is the blower moter switch on the A/C Panel.




And this is the connector that hooks to the resistor pack. I had to cut back the wiring and add new wiring until I found a striped out XJ and luckly it had the connectors still in it that I needed. I have since then spliced the new connectors in.
Hope this helps in getting you started..... :firedevil:

As 8mud stated 25 amps will smoke your wiring faster than you can blink. I got lucky and turned the A/C to the off position and it stopped smoking. Oh and BTW I had a "Good" fuse in there and it didn't blow on me. I have since changed it out, :yelclap:

Alex