Hi,

I'm a newbie to this forum. I'm pretty good with a wrench, I've restored a 1978 Chevy Impala and a 1985 Audi Coupe GT. I am a moderator on VWVortex.com, thecarlounge.net and Fourtitude.com and very active within the online Audi communities. I am the original owner of a 1993 RX-7 R1 (red, faded to pink). She has been a blast and I'm getting ready to repaint her since she's been ptretty great in terms of fun and reliability. The only non-scheduled trips to the dealer were for a bad ECU when she was only 6 months old and for a engine replacement. The car jsut wasn't rinning "right" and frankly I thinkt he dealre coundn't find the problem so they jsut said replace the engien. That was about 12,000 miles ago. She now has about 85,000 miles. Other than those 2 things, it's been nothing other than oil changes, brake pads & tires for the whole 13 years (bought in late fall 1992).

Anyway, on to why I'm posting...the AC had been workikng flowlessly all this time, never even a recharge since new. Last week as I was driving in stop & go traffic in a thunderstorm...the AC when from cold to warm very quickly. When I got home, I started troubleshooting. I discovered that the 15a fuse was blown. I threw in a fuse and checked...COLD AIR! Yeah! But then a minute or so later as I was driving downt he road...it blew again...warm air! Thinking I possibly had a bad fuse (it was old, just sitting around in my spares) I threw in another and just let her idle...it blew too. I SO need AC in southeast Virginia. It's going to be 95-98*F with heat indexes in the 105-110 range today, same tomorrow! So, I've got to get this fixed. I found a wiring diagram for the AC system within a thread here: https://www.rx7club.com/3rd-generation-specific-1993-2002-16/looking-ac-electrical-444250/ To me it looks like the fuse is for the refridgerant pressure switch and AC relay. Right? Any thoughts on what could be causing the fuse to blow? Would being low on R12 cause this? Or are we looking at a bad relay or bad pressure switch? Or am I looking at having to try to track down a short? Hope not, those can be very hard to find... TIA!

 

You're most likely looking at a short somewhere. Low or high freon pressure would trip the pressure sensor, making the AC not operate but having no effect on the fuse.

The first place I'd start is the single wire going to the AC compressor - it's near belts and other moving things that could wear a hole through it. Should be relatively easy to do a look-see on that wire.

Dale

 

/\ yep and the plug to the air pump clutch is on the same circuit. make sure it is not bare and shorted somewhere.

 

You didn't say which fuse--but there are at least two 15A fuses that will prevent AC operation. One is the A/C fuse, the other is the "cigar" fuse which supplies the coil of the A/C relay.

Note that there are more connections on each circuit than shown in the abridged schematic that I posted in the other thread; you will have to refer to other diagrams to locate those. In any event, you can disconnect loads on each circuit until you locate the culprit.

Does the fuse blow immeadiately or does it take a while? And it occurs only when the AC is on, right? OK. A quick or immeadiate blowing fuse usually indicates a short condition known as a "dead" short and is often due to a damaged, pinched or grounded wire. If it takes it a while, more than a few seconds and into minutes, it is more characteristic of an overload which could be due to a failed component such as the clutch magnet. It is possible to have an internal failure (shorted turns) where it still works, but draws exessive current. This is not common, but it does happen. Fortunately, it is easy to check. Just disconnect the compressor wire and see if the fuse still blows...

Good luck!

 

OK, maybe I'm an idiot...but where is the AC compressor? I found the air pump...but the AC compressor? I'll have to check to see how fast it blows the fuse...

 

I second the airpump circuit, I've seen bare shorted wires there cause the AC fuse to blow several times.

 

i had the same issue it turned out that there was a short in the ac compressor causing it to become a ground, poped several fuses while tring to diagnose the problem it wound up frying the harness and blew the ecu.

 

i had the same problem too it was the switch in the compressor that was faulty
needed a new compressor or to remove the switch from a good compressor

 

It's the normal 15a blade fuse, not a cigar style. I'll look for bare wires when I get home. Thanks. Oh, where is the compressor?

 

passenger side under the power steering pump.

 

You meant driver's side?

 

i had the same problem with my car.....I couldnt find any shorts in the wiring either. I literally took everything apart and test with a multimeter to see if anything grounded out that wasnt supose to be. I ended up putting a 20A in the slot and its been fine since. And if it was a dead short then I guess the 20A would of blown also. I think its just the internals of the compressor getting old...cause my car starts to overheat only when I turn on the AC? Go figure.......does any one know why this might be?

 

ummm dave i was talking about j spec cars yea thats it.... nah you are right it is the drivers, and i suk at typing.

 

Bringing this back from the dead. lolThe car was stored for the summer, didnt have time to work on it and I cant live without AC. I found that its the exact same thing with my car, but I actually had to go to a 25a fuse, 20a still popped. So, it seems whatever the issue is, it causes somewhere between a 5-9.9 amp increase in power requirements. I just did it as a test. Qustion for the forum, can the wiring hadle the extra draw without frying? If so, the AC does seem to cool just fine with the larger fuse and the car does NOT overheat.

 

Forgot to add in e-mail notification.

 

I had the same problem and it turned out to be a bad wire between the underhood fuse/relay box and the (front) relay box.

Take out the 15amp fuse and put a male spade in the right female spade of the
fuse holder. Run a new wire (with a new in-line fuse holder) to the front relay box
and splice in to the blue/black wire of the a/c relay.

I'm assuming that the 15amp fuse that keeps blowing is in the fuse box under the hood.

While I was doing the splice in the front relay box, I noticed that someone spliced in another wire in the same vicinity, at some point. So, the wires there must be vulnerable to corrosion or damage.

Hope this helps save some time, troubleshooting.

Jack

 

as a RULE : Never put a higher rated fuse in place of one that blows. Never.

it may fly for awhile but it will def cause more problems than you initaly had.

sounds like the ac clutch is in the process of seizing or possibly the air pump clutch. if it was a dead short it would blow whatever fuse you put in there. does it only blow the 15amp (correct)fuse when you engage the ac? that would lean towards ac clutch. if it just pops try disconnecting the air pump and turning on the ac and see if it blows. a clamp stlye meter would be nice so you could see the amp pull on the clutch power wire

 

It only pops the fuse when the AC is engaged. Problem began when I was driving in the heaviest rainstorm I have ever driven in. Literally I was at idle in 1st and could barely see the tail lights of the car 20 feet in front of me.