Quirky A/C Problem
06-03-2010, 01:22 PM
#1
Three Wheelin'
Thread Starter
Quirky A/C Problem
I've owned this car for ~2 months now and while the project list keeps getting shorter, this A/C problem has me stumped and I'm hoping one of you 944 gurus could point me in the right direction.
Things I have done recently/noticed/tried
Using clarks diagram on http://clarks-garage.com/shop-manual/hvac-01.htm
specifically
HVAC Unit Right Side
I sent an email to my father to get his opinion so I'll just c/p the body of that
So, am I on the right track? From my searching it seems that I can just jam something in the heater valve to keep it closed, or, the solution I preferred, just T'ing the heater valve in behind the check valve and cap the nipple on the firewall.
I observed the heater valve today for the first time under these conditions:
-cold start
-A/C on coldest, fan on highest, two switches all the way left
-idle the heater valve is closed, give a little bit of gas and it pulls it shut a little more then just seems to lose all vacuum and the valave opens again. This would correspond to me getting cold A/C at stop lights, but not after I drive away from them.
The A/C blows cold as ice (refilled with R134a a week ago) until you get lightly on the throttle, then you can hear the audible hiss of the A/C in the cabin go away and you get a nice 130 degree blast in the face. Perhaps that hiss is the vacuum leak causing all this hell?
I bought a new heater valve a month ago meaning to replace it when I had the intake manifold off but the package arrived a few days late and I had already buttoned everything up and filled the system with coolant. While I wouldn't like to do that again, if it's my only choice, then hey, more bonding time with the car, right?
The heater valve on the car does look new-ish, the plastic was still white and not that awful shade of yellow/brown death that our overflow tanks seem to love.
Thanks for the insights everyone, hope I didn't get too rambly.
Things I have done recently/noticed/tried
Using clarks diagram on http://clarks-garage.com/shop-manual/hvac-01.htm
specifically
HVAC Unit Right Side
I sent an email to my father to get his opinion so I'll just c/p the body of that
Port # 4 pulls vacuum and has the vacuum reservoir T'd into it, so it should have a constant source of vacuum whenever.
The line is then T'd, one port goes to #2 and one goes to #3. #2 is the fresh air intake flaps, #3 is the heater valve control. Both are solenoids controlled by ***** on the climate control unit, they vary vacuum, they aren't just on/off, to my knowledge.
#2 runs a vacuum line up to the blower motor, I've tested them and there are no leaks to be found there.
#3 or one of the lines from it would seem to be the culprit.
The line is then T'd, one port goes to #2 and one goes to #3. #2 is the fresh air intake flaps, #3 is the heater valve control. Both are solenoids controlled by ***** on the climate control unit, they vary vacuum, they aren't just on/off, to my knowledge.
#2 runs a vacuum line up to the blower motor, I've tested them and there are no leaks to be found there.
#3 or one of the lines from it would seem to be the culprit.
I observed the heater valve today for the first time under these conditions:
-cold start
-A/C on coldest, fan on highest, two switches all the way left
-idle the heater valve is closed, give a little bit of gas and it pulls it shut a little more then just seems to lose all vacuum and the valave opens again. This would correspond to me getting cold A/C at stop lights, but not after I drive away from them.
The A/C blows cold as ice (refilled with R134a a week ago) until you get lightly on the throttle, then you can hear the audible hiss of the A/C in the cabin go away and you get a nice 130 degree blast in the face. Perhaps that hiss is the vacuum leak causing all this hell?
I bought a new heater valve a month ago meaning to replace it when I had the intake manifold off but the package arrived a few days late and I had already buttoned everything up and filled the system with coolant. While I wouldn't like to do that again, if it's my only choice, then hey, more bonding time with the car, right?
The heater valve on the car does look new-ish, the plastic was still white and not that awful shade of yellow/brown death that our overflow tanks seem to love.
Thanks for the insights everyone, hope I didn't get too rambly.
Last edited by Scott H; 06-03-2010 at 01:43 PM. Reason: Guilty conscious made me get a membership :)
06-03-2010, 03:23 PM
#2
Three Wheelin'
Thread Starter
And the lesson for today is: Keep It Simple, Stupid.
Throughout this entire process I assumed that it couldn't be the heater flap because I would ocassionally gets blasts of cold air. Well, I took the access cover off, went to go jiggle the rod a bit to check for play, and then the plastic bit finally gives up the ghost.
1 zip tie later I have cold A/C
I'm still wondering about the function of the heater valve though, is it supposed to open and close a little bit when you work the throttle? I hear an ominous "hiss" when I stick my head into the passengers foot well. This hiss also goes away off idle. I pinched the vacuum intake line at the manifold and the hissing stopped right away, soooo?
Either way, it's 10x better than it was when I started.
Throughout this entire process I assumed that it couldn't be the heater flap because I would ocassionally gets blasts of cold air. Well, I took the access cover off, went to go jiggle the rod a bit to check for play, and then the plastic bit finally gives up the ghost.
1 zip tie later I have cold A/C
I'm still wondering about the function of the heater valve though, is it supposed to open and close a little bit when you work the throttle? I hear an ominous "hiss" when I stick my head into the passengers foot well. This hiss also goes away off idle. I pinched the vacuum intake line at the manifold and the hissing stopped right away, soooo?
Either way, it's 10x better than it was when I started.
06-05-2010, 02:55 PM
#3
Three Wheelin'
Thread Starter
Took the glove box out today to look at the vacuum assembly, no visible cracks, but if I pinch the inlet line the hissing will stop; if I pinch the outlet line to the air flaps it also stops, so I'm assuming that is where the crack is.
Before I go tearing into this anymore trying to chase a ghost, is the A/C supposed to make a hiss that sounds like a vacuum leak when you turn it on? I'll feel like a complete tool if it is...
Update:
The vac line going to the fresh air vent had a nice 1/2" gouge in it where one of the body nuts holding the A/C blower assembly to the body of the car (those little things that slip onto body and are threaded) snagged on the vac line, then when the screw was tightened down it just ripped. Dunno how long it's been like that but it's fixed now. Just have to get the friggin passenger footwell vent back on, which seems impossible unless you have small hands but long fingers.
I also cleaned the blades on the fan (they were black) and all the crap out of the coil that's under the A/C blower, as it had to be at least 80% covered with dirt/mold/stuff, so that should help the A/C flow a little better. I bought the KLA cabin filters a while back and had them in for a while but took them out when I thought I might be having A/C issues. I'll be putting them back in to keep things nice and clean in there.
Can't wait to get buttoned up and enjoy driving the car without looking like I just walked out of a steam room.
Before I go tearing into this anymore trying to chase a ghost, is the A/C supposed to make a hiss that sounds like a vacuum leak when you turn it on? I'll feel like a complete tool if it is...
Update:
The vac line going to the fresh air vent had a nice 1/2" gouge in it where one of the body nuts holding the A/C blower assembly to the body of the car (those little things that slip onto body and are threaded) snagged on the vac line, then when the screw was tightened down it just ripped. Dunno how long it's been like that but it's fixed now. Just have to get the friggin passenger footwell vent back on, which seems impossible unless you have small hands but long fingers.
I also cleaned the blades on the fan (they were black) and all the crap out of the coil that's under the A/C blower, as it had to be at least 80% covered with dirt/mold/stuff, so that should help the A/C flow a little better. I bought the KLA cabin filters a while back and had them in for a while but took them out when I thought I might be having A/C issues. I'll be putting them back in to keep things nice and clean in there.
Can't wait to get buttoned up and enjoy driving the car without looking like I just walked out of a steam room.
Last edited by Scott H; 06-05-2010 at 07:35 PM. Reason: The Porsche Gods shone their light upon me.
06-12-2010, 12:46 AM
#4
Rennlist Member
Scott, where in Orlando do you live?
Bring the car by our shop, we would be glad to help you get everything solved. Personally I don't have much A/C repair experience but the others do, and we have all the tools and A/C machines to track your problem.
Zotz Garage
1781 SR 436
Winter Park, FL 32792
407-678-6789
Bring the car by our shop, we would be glad to help you get everything solved. Personally I don't have much A/C repair experience but the others do, and we have all the tools and A/C machines to track your problem.
Zotz Garage
1781 SR 436
Winter Park, FL 32792
407-678-6789
