donnieknoxville

I've owned my car for approx 10 year now and finally had a shop in town get my A/C working 2 months ago. System had pressure and they added new 134a, etc. Everything worked great for about 6 weeks.

Earlier this week I noticed that the A/C blower fan wasn't pushing any air through the vents when I started the car. After about 1/2 mile of driving, A/C just started working on its own. Same thing occured for the next several days until recently when I can't get the fan to come on at all.

Any thoughts???

Fuses look good but could this be a relay, fan, resistor, temp sensor, etc.? How would I test electical to rule out various components?

Thanks,

Don

jwilson95

Definitely the Porsche AC gremlins....

rusnak

Start the AC with the engine running, and see if the clutch clicks on. You'll see the center section spinning. Either that, or click the clutch on and try to turn it by hand w engine off.

If the clutch works, then it could be the relay or circuit going to the blower. My '84 still has the resistor pack from the 'SC, so I'd suspect that. I don't know about '87. Funny thing though, mine started doing the same thing. All I've had time to do so far was check the alternator output.

tomphot

Please note - it is advised that the A/C should never be run with the rear deck open - when checking the clutch - if you can keep the deck mostly closed and peek in - that would be the thing to do.

Ed Hughes

It would appear that it is terminal. The diagnosis is that it has to come out.

donnieknoxville

The center section of the compressor does not turn with the engine running but I'm not getting any electrical current to the compressor anyway (tested with V-meter).

The front blower motor is shot - frozen up completely - so that needs to be replaced.

The bi-metalic switch appears to run a current through a resistor coil that looks like a spring and then at some point (temp or current related), an electromagnetic field pulls an arm down to close the circuit. No idea how to test this - any thoughts.

Anyone know how to get the electrical cover off of the evaporator (aside from removing the one screw).

I swapped the red relays from other positions on the fuse panel (same part #) and no change. Cant get the air to blow into the passenger compartment.

I know the DME is involved in the electrical diagram - any chance its the culprit?

Don

theiceman

if your refridgerant has leaked back out of the hole they didn't fix when they recharged ( probably in your evapirator ) , the clutch will not engage due to low system pressure .....

also if your fan isn't working your evaporator will freeze releasing the clutch . see if it works when you first turn the car on , if it does your evaporator is freezing....

g-50cab

You guys are trying to make this more complicated than it really is - he's talking about the fan in the front smuggler's box. my guess is it's either the fan switch on the console - or the fan motor - (but first check fuses and connections (there is a plastic connector that should be on top of the fan assembly). Check those first before messing with anything else

theiceman

g-50 check his second post ....

whalebird

It's OK to run the A/C with the deck open. It helps to have a fan blowing up thru the condensor. For diagnosis, don't worry about air flow over the condensor until you have the cluch engaging. I would put a set of gauges on it. I know this seems non productive, but an unsuspecting technician can easily throw the pressures off when converting miles of a/c lines over to 134.
Check all of the fuses - twist them in their sockets. Look for overheated fuse terminals on the fuse block. A failing blower will overload the circuit and damage the relay/wiring/fuse panel.
I would have to agree with g50cab in that this is such a simple a/c system that diagnosis is a piece of cake for an experianced Porsche tech.
Good luck

g-50cab

Doh - yes you have many issues - could just be a compressor - could be a combo compressor that's burned up your temp switch. Either way you are looking at an expense. At this point I would look at one of the all encompassing kits from rennaire or griffiths.

The evaporator comes out with the screws/bolts around the perimeter AND there are two screws that extract air out of the passenger footwell - don't forget those or you will never get the little bugger out. The top of the evaporator is held on with clips that are around the perimeter - and are virtually impossible to get back on with the evaporator secured in the smugglers box. (and if you can you need to go to medical school and be a surgeon)

g-50cab

oh - and one more thing - unless you have replaced all your 22 year old hoses (and it's shocking how many feet of hoses there are in these small cars) then you are wasting your time charging the system - they will leak.

donnieknoxville

Many thanks to all those who commented. I learned a lot more about the system than I expected.

The first thing I did was check the fuses (and by checking, I mean visually inspected) - then I started unbolting everything. Once I knew where everthing was, I pulled out my trusty electical diagram to start checking resitance and volts. Since the resistor (bi-metallic switch) was on the top of the list, I started there. No current. So I moved to the front condenser blower motor. No current. Then I want to the evaporator blower motor. Again, no current. So I went back to the fuse board and looked again - fuse good.

I then did what I should have done the first time, I went to wiggle the fuse, and unlike the others, it wiggled slightly. When I removed it I discovered that the metal strip was still intact but that the plastic fuse had melted a little, shrinking slightly in lengeth and causing the top contact to fall just short of making contact with the metal bus bar. Replaced with new fuse and everything was fixed. I then spent another hour putting everythign back together. In the process though, I discovered that my front condenser blower motor was frozen solid. So - I'm going to order a new one of those.

Thanks again,

Don

UberXY

If your pressure is low, the clutch won't engage because the low pressure switch will prevent the clutch wire from delivering current. This is a good thing.

If your pressure is low, try to figure out where the leak is. The easiest place to start is to check the six o-rings on the compressor - once on each hose, and four under the compressor manifold. You can get a complete o-ring kit at Autozone for about $8.00.

I just replaced a Denso compressor that was leaking from the seal on the front of the mainshaft - worked fine one day, did not work the next. No repair possible, so I put in a reman unit. Easy work, and while I was there I replaced the six o-rings.

Sounds like you got the blower motors covered.

rusnak

Since the OP solved his problem, I thought I'd post a few thoughts on mine.

My front condenser fan is working, and the ac compressor is working. I'm ruling out the #2 fuse. There is power to the grn/wht wire at the ac blower switch on the center console, and at all 3 contacts on the bi-metallic switch.

The problem is that the evaporator fan does not blow, and there is no power at the red/wht connector at the fan connector. So, I need to pull the center console switch, test the red/wht wire and the others in series with the switch on. At this point, I'm thinking it may be the ac blower switch or the AC relay, which I have not checked.

It's just too bloody hot outside to work for more than 15 mins at a time, and I'm really busy at the office anyhow.