Introduction and Thank You!
07-05-2010, 08:38 PM
#1
Rennlist Member
Thread Starter
Introduction and Thank You!
Hi everyone,
My name is Craig and I live in St Louis, MO. At the end of the workday and on weekends, I am a car guy and do a fair amount of my own wrenching. Last fall I completed a restoration on a 1985 944/2 NA that I owned since birth. Great fun and great outcome. As that project neared completion, I decided to leverage all that 944 knowledge and purchase the Porsche I always wanted: a 928.
It didn't take very long to find a great car. Shortly after Christmas, I purchased Jim Morton's Black/Cashmere 1993 928 GTS 5 sp and had the vehicle Fedexed to St Louis. Bill Ball did the PPI and he confirmed what I already suspected: the car was in excellent condition and had a long history of being loved by each of its owners.
Since taking possession of the car, I've done a few minor things: fixed the door stops, added skid plates, installed a short shifter, replaced the front spoiler and a few of the plastic pieces in the fender wells. In doing so, I got to do business with Roger, Carl (and even had a painless transaction with Mason).
Last week however, the A/C compressor clutch seized in 95F weather. That it happened as I was pulling into my driveway was a small miracle. In the 50 feet from street to garage, the A/C clutch and drive belt melted.
Jumping on Rennlist, I could tell this was going to be much more of an adventure. After consulting Roger, I had a new compressor, two expansion valves, drier and o-rings in the mail. In the meantime, I flushed out the entire system. This weekend I reassembled the lines, the expansion valves,the drier and added ester oil. In addition, I relocated the low pressure Schrader valve so that anyone can reach it, not just guys with small, fireproof hands.
With the system vacuumed for 3 hours and observed for leaks overnight, I jumped the low pressure switch and added a few cans of R12. Started the car - warm air. Also there were no changes in low or high side pressure. After a few minutes I confirmed that the clutch on the new compressor was not engaging. When jumpered to the 12v post, the clutch worked fine. I then measured 0.3 volts at the clutch control wire.
Back to Rennlist. It took 5 minutes to find several threads about A/C clutch failures that also took out the clutch control relay buried in the A/C control unit. Armed with a set of step by step instructions, I was able to remove the control panel, disassemble it, find the relay, unsolder it and run external wires to a heavy duty Radio Shack relay. I reassembled the whole thing this afternoon and voila, the A/C compressor was behaving well.
I added a bit more R12 late this afternoon and went for a test drive.
External Temp = 95F
Temp at center vent: 68F
High/low side pressures @ 1500 RPM: roughly 240/40
I'll recheck it in a few days and perhaps adjust the charge (which might be a bit high).
So that's the end of my story for today. I'm sure there will be many more opportunities to interact with all of you in the future. After all, these were high strung vehicles from the get-go. And now it is 17 years later.
At some point, maybe I will be able to contribute useful knowledge to the group. In the meantime, I'm very pleased with this great car and appreciate the collective knowledge of this group.
Best regards,
CraigL
My name is Craig and I live in St Louis, MO. At the end of the workday and on weekends, I am a car guy and do a fair amount of my own wrenching. Last fall I completed a restoration on a 1985 944/2 NA that I owned since birth. Great fun and great outcome. As that project neared completion, I decided to leverage all that 944 knowledge and purchase the Porsche I always wanted: a 928.
It didn't take very long to find a great car. Shortly after Christmas, I purchased Jim Morton's Black/Cashmere 1993 928 GTS 5 sp and had the vehicle Fedexed to St Louis. Bill Ball did the PPI and he confirmed what I already suspected: the car was in excellent condition and had a long history of being loved by each of its owners.
Since taking possession of the car, I've done a few minor things: fixed the door stops, added skid plates, installed a short shifter, replaced the front spoiler and a few of the plastic pieces in the fender wells. In doing so, I got to do business with Roger, Carl (and even had a painless transaction with Mason).
Last week however, the A/C compressor clutch seized in 95F weather. That it happened as I was pulling into my driveway was a small miracle. In the 50 feet from street to garage, the A/C clutch and drive belt melted.
Jumping on Rennlist, I could tell this was going to be much more of an adventure. After consulting Roger, I had a new compressor, two expansion valves, drier and o-rings in the mail. In the meantime, I flushed out the entire system. This weekend I reassembled the lines, the expansion valves,the drier and added ester oil. In addition, I relocated the low pressure Schrader valve so that anyone can reach it, not just guys with small, fireproof hands.
With the system vacuumed for 3 hours and observed for leaks overnight, I jumped the low pressure switch and added a few cans of R12. Started the car - warm air. Also there were no changes in low or high side pressure. After a few minutes I confirmed that the clutch on the new compressor was not engaging. When jumpered to the 12v post, the clutch worked fine. I then measured 0.3 volts at the clutch control wire.
Back to Rennlist. It took 5 minutes to find several threads about A/C clutch failures that also took out the clutch control relay buried in the A/C control unit. Armed with a set of step by step instructions, I was able to remove the control panel, disassemble it, find the relay, unsolder it and run external wires to a heavy duty Radio Shack relay. I reassembled the whole thing this afternoon and voila, the A/C compressor was behaving well.
I added a bit more R12 late this afternoon and went for a test drive.
External Temp = 95F
Temp at center vent: 68F
High/low side pressures @ 1500 RPM: roughly 240/40
I'll recheck it in a few days and perhaps adjust the charge (which might be a bit high).
So that's the end of my story for today. I'm sure there will be many more opportunities to interact with all of you in the future. After all, these were high strung vehicles from the get-go. And now it is 17 years later.
At some point, maybe I will be able to contribute useful knowledge to the group. In the meantime, I'm very pleased with this great car and appreciate the collective knowledge of this group.
Best regards,
CraigL
07-05-2010, 09:14 PM
#3
Rennlist Member
Welcome Craig. You got a peach of a car. The 928 may be high strung, but to paraphrase a purported to remark about 1930's era Bugatti's "Two weeks of the pain are worth two hours of the driving." I have only owned my '90 S4 for a little over a year and am still amazed at just how capable a car the 928 is.
I hope you will bring the car down to the NW Arkansas area some time so I can drool next to it.
Mike
I hope you will bring the car down to the NW Arkansas area some time so I can drool next to it.
Mike
07-05-2010, 09:15 PM
#4
Team Owner
that center vent temp is pretty hi you should be seeing 35 degrees or less.
I would do a vacuum check of the pods as it sounds like one or more may have a hole in it if this happens then the heater control valve will not stay closed and warm air will be mixed with the cooled air
go to www.928gt.com and print off Wally tips for the HVAC system diagnosis its on page 2 under tips and links
I would do a vacuum check of the pods as it sounds like one or more may have a hole in it if this happens then the heater control valve will not stay closed and warm air will be mixed with the cooled air
go to www.928gt.com and print off Wally tips for the HVAC system diagnosis its on page 2 under tips and links
07-05-2010, 11:03 PM
#5
Under the Lift
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Craig:
Glad you checked in here. I hope you are enjoying all the goodies Jim put on that car (Ferrari brakes, big rotors, color matched leather covered Recaro SRDs, hot cams, unique airbag steering wheel).
Too bad about the compressor and the headunit relay. Nearly all of us have had the same adventure due to the age of these cars. Sounds like you are very up to the challenge of the 928 idiosyncrasies.
68F from the vents at 95 ambient is pitiful. This system should be able to generate a 55-60F differential versus outside temp. Initially I was startled to read you put in a couple of cans of R12, but then I remember this car is a Euro delivery 92 even though titled as a 93. So, I gather it was R12 to begin with and not R134a as a common 93MY would be, right? You flushed and replaced the expansion valves because the compressor, not the clutch per se, seized. So, you COULD have reverted to R12 from 134a regardless. Anyway, a couple of cans of R12 is not enough. The proper charge is 1150gm. Most R12 cans are 12 oz or 340gm. So, you need a little more than 3 cans. Theoretically, the freeze switch will cycle the compressor off at an evaporator temp of 32F and on again at 40F, but my car puts on 26-34F air at the center vent with an ambient temp of 88F. Bone chilling! Yours should at least get into the low 40s at 95F ambient unless the car is very heat-soaked. You could have an issue with the heater valve, as Stan (MrMerlin) mentioned, or the mixing door motor, particularly if the rear AC is a LOT colder. However, if turning on the rear AC causes the front AC to get warmer, a low charge is more likely the issue.
Enjoy!
Glad you checked in here. I hope you are enjoying all the goodies Jim put on that car (Ferrari brakes, big rotors, color matched leather covered Recaro SRDs, hot cams, unique airbag steering wheel).
Too bad about the compressor and the headunit relay. Nearly all of us have had the same adventure due to the age of these cars. Sounds like you are very up to the challenge of the 928 idiosyncrasies.
68F from the vents at 95 ambient is pitiful. This system should be able to generate a 55-60F differential versus outside temp. Initially I was startled to read you put in a couple of cans of R12, but then I remember this car is a Euro delivery 92 even though titled as a 93. So, I gather it was R12 to begin with and not R134a as a common 93MY would be, right? You flushed and replaced the expansion valves because the compressor, not the clutch per se, seized. So, you COULD have reverted to R12 from 134a regardless. Anyway, a couple of cans of R12 is not enough. The proper charge is 1150gm. Most R12 cans are 12 oz or 340gm. So, you need a little more than 3 cans. Theoretically, the freeze switch will cycle the compressor off at an evaporator temp of 32F and on again at 40F, but my car puts on 26-34F air at the center vent with an ambient temp of 88F. Bone chilling! Yours should at least get into the low 40s at 95F ambient unless the car is very heat-soaked. You could have an issue with the heater valve, as Stan (MrMerlin) mentioned, or the mixing door motor, particularly if the rear AC is a LOT colder. However, if turning on the rear AC causes the front AC to get warmer, a low charge is more likely the issue.
Enjoy!
07-05-2010, 11:36 PM
#6
Rennlist Member
Hi Craig,
Welcome to the club, these are great cars.
Bill kinda said everything, I went through my a/c system this year and now it does blow very cold, I"ve seen less than 30F at the center vent with an outside 90F, I went for a short drive last Thursday, it was only when I got back that I realized how cold my right arm was.
Post some pics when you can.
Welcome to the club, these are great cars.
Bill kinda said everything, I went through my a/c system this year and now it does blow very cold, I"ve seen less than 30F at the center vent with an outside 90F, I went for a short drive last Thursday, it was only when I got back that I realized how cold my right arm was.
Post some pics when you can.
07-06-2010, 12:45 AM
#7
Team Owner
Bill thats a great idea i hadnt thought about a low charge .
The diagnosis I gave comes right off of the car i am working on now as i was also getting 60 deg temps from the center vent.
after a pod check i found 2 leakers that had previously tested good this kept the vacuum low and thus the heater control valve would never close as it should , with the pods repaired and the system still slightly low on freon I am getting 30 degrees at the vent with OAT at 85
The diagnosis I gave comes right off of the car i am working on now as i was also getting 60 deg temps from the center vent.
after a pod check i found 2 leakers that had previously tested good this kept the vacuum low and thus the heater control valve would never close as it should , with the pods repaired and the system still slightly low on freon I am getting 30 degrees at the vent with OAT at 85
