[barth7]

My AC was cooling fine and then all of a suden, right before going to the Porsche 250, it decides to die on me. I think it's a relay somewhere, but not sure. Here are the symptoms:



- The light on the AC switch on the dash illuminates

- The secondary fan kicks in and it blows harder

- There seems to be no drag on the engine, so I assume the compressor is not engaging

- The air does not cool down at all when going from vent to AC

- Usually, you can hear a relay, maybe in the dash, kicking in when keeping the temp in the car - it's not engaging



How can I check the relay under the hood? What else should I try? Thnaks!



-Bart



P.S. The P250 was pretty good - at least it didn't get rained out.

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[MAryland968]

Bart,



I would check to make sure you have enough freon. Unplug the low pressure cut out switch from under the hood near the drier on the drivers side of the car. Use a piece of wire and jumper the plug that you pulled off the switch. Start the car and turn the A/C on - if it starts to cool, you know that you are low on freon. If the car is a '93 or newer, you can get a recharge can of R-143 from an auto parts store and refill your freon level.



Phil

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[968 Cab]

Start with simple things – you can do a few things before getting under the car:



1. Open the engine hood and at the front of the car at the DS, locate the AC receiver dryer – it should he an alum color cylinder about 2.75” round and 7” tall mounted on the DS fender. There is a small glass “window” – about ¼” round. Clean it off with a cloth and start up the car, turn on the AC. If you see bubbles/froth/foam, you are short of R134 (used in your 94 – 92 cars use R12 which is NLA) and need a top up / recharge. If you cannot see any fluid flow, then the compressor is not working. Go to step 2



2. check the fuse box – Fuse #29 – 7.5A. Replace and it if blows, you have a short or failed compressor clutch that might be pulling too much current. If it’s OK then proceed to step 3



3. Relay G19 – get someone to turn ignition switch to pos#2 – panel lights on, but engine NOT running. Stand near the DS by the fuse box and with the cover off, you can have your assistant push the AC button on and off. You should hear the AC compressor clutch CLICK on and off – quite loud. If you can hear that, your compressor clutch and relay should be fine. If NO sound, go to step 4



4. Pull relay G19 out of the fuse box. If you have a spare or another 944/968 around, just do a swap and see if that works. Sometimes, you can gently “tap” the relay to free up sticking contacts – a “failed” relay is rare - more likely, the relay contacts are corroded from arcing – you can carefully open these up and with a narrow strip of 400 grit sandpaper you can clean them off and get it working again.



5. If all that checks out, get the car up on jackstands and get underneath to check to make sure the Power Wire to the AC compressor clutch has not fallen off, chaffed, etc. That is not uncommon.



If all that checks out and the AC still does not work, check out the section on AC in Clarks’ Garage for servicing. Do a Search on the technical section of these forums and the Rennlist forums. There’s a lot about servicing your own AC – it’s actually pretty simple stuff – but you have to maintain cleanliness if you open up the system and follow procedures to recharge the system if it is low. Still easy to do and possible for DIY.



Good luck!

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[barth7]

Thanks Cab, that looks like an excellent guide. I'll do those today, I hope.

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[pors968]

Check Heater control valve(HCV) above Oil filter is closing/opening when A/C is on and off. you can check this visually. I'm interested to know what was wrong. please post the findings.

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[968 Cab]

[quote name='pors968' date='Jul 31 2006, 09:23 AM']Check Heater control valve(HCV) above Oil filter is closing/opening when A/C is on and off. you can check this visually. I'm interested to know what was wrong. please post the findings.

[right][post="24820"]<{POST_SNAPBACK}>[/post][/right][/quote]



The plastic OEM Heater Control Valve is prone to failure as it is so close to the hot exhaust. The one in my car split along the glue seam one day! But instead of replacing with the Porsche OEM unit (I had a spare), go buy the equivelent part from Audi that is metal.



The HCV seldom gets "stuck" open to end up with a blast furnace. What does fail are the plastic clips for the heater flaps inside the cabin. Uncontrolled hot air from the heater means that the dreaded heater control "plastic clip" broke off! A temporary limp home solution is to shut down all the Air Con and deflect all the heat to the defroster to try to keep cool.



There is a Nov 2000 article in Excellence (pg 135) that describes the re&re repair procedure. These are dealer only parts – you need 2 clips and 2 retainers - a total of $3.75!



P/N - plastic clip 944-572-314-00

P/N - metal retainer 944-572-217-00



They are shown as #14 & 15 in PET illustration # 813-00 and they look like this:

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[barth7]

I know about the HCV issue. Some people reccommend staying with the plastic Porsche part and replacing it every XXXXX miles. That's probably what I will do.



Dumb question here, but is that not the low pressure line right there at the drier? I think it is just low of freon because everything electrical seems to be okay (fuse OK & relay responds as it should). I bought a can a R134a, but the fitting doesn't attach to mine. Maybe that is the high pressure one there.



Haven't downloaded the manual yet, but I will search for some info. Thanks for any help.



-Bart

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[968 Cab]

[quote name='barth7' date='Aug 1 2006, 06:37 PM']I know about the HCV issue.  Some people reccommend staying with the plastic Porsche part and replacing it every XXXXX miles.  That's probably what I will do. 



Dumb question here, but is that not the low pressure line right there at the drier?  I think it is just low of freon because everything electrical seems to be okay (fuse OK & relay responds as it should).  I bought a can a R134a, but the fitting doesn't attach to mine.  Maybe that is the high pressure one there.



Haven't downloaded the manual yet, but I will search for some info.  Thanks for any help.



-Bart

[right][post="24889"]<{POST_SNAPBACK}>[/post][/right][/quote]



Did you see bubbles in the AC sight glass on the receiver dryer? You should see some clear fluid moving when you hit the AC switch to "on". If there are bubbles / foam that is a good sign - just low on R134. If it looks completely DRY, that probably means a bad AC line or compressor and that is more work, buy you can DIY. If there is clear fluid flow and no foam/bubbles, then there is another problem somewhere - don't put any more R134 into the system if there is a good charge.



That is the HIGH PRESSURE fitting on the top!!! The Low Pressure Fill valve is right on the compressor, under the car!! (yep, what a great place for that....) you have to get under the car (jackstands please), remove the belly pan, grope around in the dark, clean off the grease and gunk on the fitting BEFORE you attach and try to fill! I just love getting under a car with a running engine and whirling things all around.... fitting that R134 valve on the fitting and then holding the can upside down as close as you dare get your hand etc to that moving belt!!!



Anyway, get the manual / Clark's Garage has a good write up, and BE CAREFUL!! Good idea to wear some goggles / glasses to protect your eyes when you are doing a fill too. The can gets pretty cold too as the R134 goes gaseous state during the fill process, so be forewarned.



Whatever you do, be careful and get someone to help start the car, turn on the AC, keep an eye on the sight glass on the receiver dryer (don't overfill the R134 as the AC will be less effective if overfilled).

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[barth7]

Aw hell, that's what I was afraid of. I've, obviously, never done much AC work. I couldn't tell squat from my sight glass, really. I do have the can with gage, so I was gonna check that before I put any in.



Thanks again, cab.



-Bart

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[rhudeboye]

Having the same prob. Im on vacation now but will follow the steps above to try an solve my AC prob. Just wanted to drop in and thank everyone for their help. Its HOT over here on the East Coast!

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[orphanowner]

[quote name='968 Cab' date='Aug 1 2006, 10:08 PM']Did you see bubbles in the AC sight glass on the receiver dryer?  You should see some clear fluid moving when you hit the AC switch to "on".  If there are bubbles / foam that is a good sign - just low on R134.  If it looks completely DRY, that probably means a bad AC line or compressor and that is more work, buy you can DIY.  If there is clear fluid flow and no foam/bubbles, then there is another problem somewhere - don't put any more R134 into the system if there is a good charge.  [right][post="24897"]<{POST_SNAPBACK}>[/post][/right][/quote]



Great troubleshooting guide except for one thing. my 1994 968 doesn't have a sight glass in the dryer. This may have been a 134 thing, as the bubble method is less accurate on 134 or some kind of running production change. The dryer on my car is original. Let's hear a count, how many 134 cars have a sight glass?



On the cars that have a sight glass, 968 cab did you right!

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[barth7]

Aha! I think mine doesn't have a sight glass, either. It has a allen head set screw in the top of the drier, I think. If it is a sight glass is is terribly hard to see anything.

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[sasilverbullet]

Most sight glasses are gunked up and need to be cleaned off. Personally I've never seen a drier without a sight glass.



Shine a BRIGHT light on top of the thing and wipe with a rag w/wd-40 sprayed on it and wipe,wipe,wipe and it should show up...



But, I've been wrong before! <img src="/forum/images/smilies/968/sad.gif" class="smilie" alt="" />

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[flash]

mine is a 94 with code 718 (making it really a 93)



it is a 134 car and has a sight glass

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[968 Cab]

[quote name='sasilverbullet' date='Aug 2 2006, 09:27 AM']Most sight glasses are gunked up and need to be cleaned off.  Personally I've never seen a drier without a sight glass.



Shine a BRIGHT light on top of the thing and wipe with a rag w/wd-40 sprayed on it and wipe,wipe,wipe and it should show up...



But, I've been wrong before!  <img src="/forum/images/smilies/968/sad.gif" class="smilie" alt="" />

[right][post="24909"]<{POST_SNAPBACK}>[/post][/right][/quote]





If seen a few replacement RD units without a sight glass, but they are rare / cheap replacement units. Just about every OEM of any make I've encoutered had them.



If all fails, drop by any auto AC shop on a "slow day" - best are the smaller non-chain shops and if you catch the owner in a good mood, they will even do a simple leak test for you at modest or no charge. What you don't want to do is put refrigerent of any sort into the system if there is a leak or if it is already full. The simple way to tell is via the sight glass.

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[orphanowner]

[quote name='968 Cab' date='Aug 2 2006, 10:24 AM']If seen a few replacement RD units without a sight glass, but they are rare / cheap replacement units.  Just about every OEM of any make I've encoutered had them. 

[right][post="24912"]<{POST_SNAPBACK}>[/post][/right][/quote]



Right...here is a pic from my 1994 968 (2/94 production) that absolutely has not had the drier replaced. My Jetta also has a O.E. 134 drier without a sight glass.

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[mitch968]

My '92 was converted to 134 at some point. I also do not have a sight glass.

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[flash]

bummer - wonder why they did that?

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[968 Cab]

Looks like you have to go get a shop to check if there is a charge or leak in the system. Just another way to make owners go to the dealer for service work!?!?!!!



I had an independent AC shop check my son's 944NA for AC leaks, and they did not charge! They used a shot of nitrogen into the system to look for leaks - we found a bad HP line off the compressor.



In the end, I installed a new line, rebuilt compressor and went to a R12a hydrocarbon refrigerant - all for under $400. The R12a worked so well that I've now done 3 more 944/951/968 with it. Best of all, no need to evacuate the system "pull a vacuum" as the R12a is compatible with R12, R134, esther oils etc and R12a tolerates water (the apparent reason for pulling the vacuum in the first place). I've had no problems at all over 2 years now and the systems all blow COLD, even parked over the winter for 6 months.

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[Ryan]

Correct me if I am wrong here, but if you are low enough to trip the low pressure swith on the system, the compressor in not going to run. How are you going to see any activity through the sight glass if the system is not working???



I had the system in my 944S quit on me and I hooked up a can of 134a to the low end with the car running and the A/C switch on. At first the compessor would not come on, but after the can of gas brought the pressure up to the point of bypassing the switch, it kicked on and sucked the can dry. System worked after that.

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