Dumb A/C Troublshooting Question

greglepore · 05-28-2003, 03:11 AM

I have an 85 Targa that hadn't been driven much in the last 2 yrs. Didn't check the A/C at purchase (car was a deal and I didn't really care). Now that a repaint is just about done, I'm putting the car back together. Happened to check the A/C the other day and nothing happens when I turn on the fan to any position. Fuse checks ok. I presume there is low freon pressure-would the pressure switch just disable the compressor or the whole circuit? What would be the troubleshooting tree from there? Relay first, or does relay only affect compressor clutch?

APKhaos · 05-28-2003, 04:58 AM

Is the trunk-mounted condenser fan coming on when the fan switch is in any of the on positions? It should, even with ignition ON but engine not running. If not, its possible the the AC relay is suspect.

Joeaksa · 05-28-2003, 05:07 AM

If you send me your private email address I will send you a copy of a "Up Fixing der Porsche" article that came out years ago about the 911 A/C system.

JoeA

greglepore · 05-28-2003, 11:02 AM

Joe-sent you a pm. Thanks. The fan doesn't run with the engine running or the switch in the on position. Jumping power to the fused side of the a/c fuse runs the fan.

greglepore · 05-29-2003, 08:07 AM

Well, did troubleshooting today, and no luck. Relay in smuggler box tests fine, but there's no a/c power to it. Fan runs when putting 12v direcly. Couldn'd find power at the connector under the floorboard on either side under any condition. Fused side of fuse has 12v. I have to wonder if pressure switch cuts power to entire circuit. Couldn't readily find it to jump.

ruf-porsche · ruf-porsche's Garage

The temperature switch on the console also control power to the compressor clutch and condensor fan. See if you have power at the Temp. switch when you turn on the A/C fan switch. For maximum cooling the temp switch should be turn fully clockwise.

Decolliber · 05-29-2003, 10:21 AM

My a/c stopped working a few weeks ago and it was corroded fuse. The fuse looked ok (not broken) but the ends were corroded enough to prevent a connection. Cleaned them with sand paper and the a/c worked fine.
I have also had the front a/c relay fail, but my recollection is that the relay just operates the front condensor fan, so a/c will still work but you get less cooling?
In case you missed all the previous threads on this, make sure you put a 7 amp fuse in the front condensor fan power line.

A slightly different question. Do we have to worry about the supply of R12 running out? If so, can I stock up? How? My a/c needs a recharge every one or two years.

Decolliber · 05-29-2003, 10:24 AM

One trouble shooting tip I recall from Bentley: turn on the ignition and then turn on the a/c switch on the console. You should hear a "click" from the engine compartment. This tells you ... (I dont have Bentley here with me at work).

ruf-porsche · ruf-porsche's Garage

Quote:

Originally posted by Decolliber

A slightly different question. Do we have to worry about the supply of R12 running out? If so, can I stock up? How? My a/c needs a recharge every one or two years.

Kinda too late to stockup on R12. You need to be certified in order to buy the stuff these days. Shoulda stock up on R12 when it was on sale for 2 cans for $.99 at Pep boy (wink wink) many moons ago. The supply of R12 will never run out as long as people are willing to pay for it.

Now would be a good time to stock up on R134a. You don't need to be certified to buy it right now.

ruf-porsche · ruf-porsche's Garage

Quote:

Originally posted by greglepore
Jumping power to the fused side of the a/c fuse runs the fan.

You could have a bad connection at the fuse. Check the fuse and the terminals.

greglepore · 05-30-2003, 05:35 AM

Actually, that was wrong, but thanks. It runs something under there (headlight washer pump?) but not the fan.

ruf-porsche · ruf-porsche's Garage

Quote:

Originally posted by greglepore
Actually, that was wrong, but thanks. It runs something under there (headlight washer pump?) but not the fan.

The thing under the headlight washer pump is the FAN for the CONDENSOR which is a part of the a/c system.

It seems to me that the FAN for the EVAPORATOR (the thing that blow cold air into the interior) is not working.

Could be the blower/ AC switch on the console or the evaporator resistor unit is bad. You mention that there was no power going to the relay in the smuggler box. Contact 30 should always be hot. Contact 87 should only be hot if the ignition switch is on (running position, not accessory position).

If contact 30 is not hot, than you have a break in the wire from the fuse box to the relay.

greglepore · 05-30-2003, 11:19 AM

Ok, I'll try that tomorrow, will run a new lead directly from the fused side of the circuit to 30. What I suspect may be happening is that the power to 30 is fed thru the pressure switch (the jpg of the upfixin article has a diagram, but I couldn't read the one graciously emailed to me) and that a lack of system pressure cut the entire circuit. Pure speculation, but I'll check continutiy on wire to 30, then try a direct jumper. Thanks for your help.

ruf-porsche · ruf-porsche's Garage

Low freon pressure will prevent the clutch for the compressor from engaging, but the fan for the evaporator should run.

Without the compressor running, you will know you have an ac problem when all you get is hot air.

greglepore · 05-31-2003, 05:17 AM

RUF-Found it! Its a PO issue. He had H4's installed by a local (famous) dealership and they did a relay as part of the install. The stock headlight fuses are now unconnected, and they added a factory add on fuse panel (not sure why-4 fuse). I assumed these were just h/l's, but the a/c main is moved to that block as well! Found it by chance checking continuity from the #30 wire to all fuses. Fuse was blown, a/c now works. Have no idea what is hooked to a/c fuse-I'll have to check the wire code and post later. Anyway, thanks for all your help!

BTW, I picked up a copy of Motor at my mechanic's. Had an excellent article on DIN wiring codes. I didn't realize that the relay numbers are standardized, and having the codes is very helpful. I'd make a copy available, but don't have the capability-I suspect the info is on the web somewhere.

Wil Ferch · 05-31-2003, 05:49 AM

That's smart ( famous dealership?)...putting multiple loads on the headlight circuit... fer-chrissakes.Headlight circuit should not be shared. Jees...where are these people's heads anyway??

---Wil Ferch

ruf-porsche · ruf-porsche's Garage

Hey Greglepore

Glad to hear that the A/C is working. Does it blow cold air? Surprise that the freon hasn't leak out without use for two years. Normally the seal dry out if you don't run the compressor occassionally.

EDIT:
Oh by the way, don't connect the evaporator motor relay with the fuse for the condensor motor. The two combine draw too much current to evetually cause a problem. I read somewhere on the net that the two should be separated. If I find the thread I'll post it.

greglepore · 05-31-2003, 01:12 PM

Wil-Maybe I wasn't terribly clear. The add on panel holds four fuses, none shared. I just assumed (jerk that I am) that it was hi/low right/left. Nah.

Ruf-I'm shocked. It blows cold air-now, it was only 80 and humid here today, but I'll get measurements with the stock setup once it gets hot (is it ever here in the East?) then additional measurments with the Procooler installed. I'll keep the same refrigerant for consistency's sake, but am probably eventually changing over to Freeze 12 or similar, although my a/c guy, who does a lot of oddball street rod systems but no P-cars, swears I'll be content with 134a. Doubt that.

BTW, removed the bowtie and wow, what a difference. Will drill the second hole eventually. I have a stock center vent that was made surplus when I updated the dash and needed to purchase a later vent, and I'll duct to that.

ruf-porsche · ruf-porsche's Garage

Quote:

Originally posted by ruf-porsche
Hey Greglepore

Glad to hear that the A/C is working. Does it blow cold air? Surprise that the freon hasn't leak out without use for two years. Normally the seal dry out if you don't run the compressor occassionally.

EDIT:
Oh by the way, don't connect the evaporator motor relay with the fuse for the condensor motor. The two combine draw too much current to evetually cause a problem. I read somewhere on the net that the two should be separated. If I find the thread I'll post it.

From the technical section
you can view the entire articel at

http://www.pelicanparts.com/techarticles/mult_AC_faq/Mult_AC_faq.htm

A word about Fuses, circuit breakers and relays!!

For several years, the factory made the same mistake on every car with a/c. When they wired the fuse board on the '76 to about '79, they wired the Evaporator. circuit together with the Front Condenser. Fan circuit. So that all the elec. load was through ONE fuse. Well since those ceramic fuses can hardly handle 20 amps. the load of 30 or 35 amps. was way too much for them. The connectors turn blue, get loose and will actually melt. Check your car and if the second fuse from the back of the fuse board is distorted see if the red/white wire is connected with the red/yellow wire. If it is, separate them and connect one of them to the next fuse which should be empty. A very good substitute for these fuses or any fuse that seems to be overloaded (that is , gets hot ) is a circuit breaker. A c.b. can be wired with a tighter connection, won't blow at the slightest provocation, and will reset itself automatically.

Most all of these a/c's will have a Relay somewhere in the circuit mainly to protect the delicate switches from the high loads of the motors. Most over looked is the Factory relay located in the heater box next to the Evaporator.

greglepore · 06-02-2003, 05:18 PM

Well, now that you mention it, the red/white and red/yellow have been seperated. The car did have a condensor motor replacement recently (the PO was meticulous about having the "famous dealer" keep the car up mechanically, the pile of receipts is almost humerous) but that is why I bought the car even though it needed cosmetics in a major way. Suspect they seperated the fuses when they did the condensor motor.

Thanks again for your insight.