C3 A/C / ventilation system - troubleshoot vacuum
Years ago, the great running A/C in my 1977 started leaking and quit working shortly after.
As (here in Germany) I could not find anyone to replace the compressor front/shaft seal (which appeared to be the "simple" culprit), I had to have the R4-compressor replaced (which was not the original one, so not much grief). While at it, I also had the drier bottle replaced at the same time.
Unfortunately R12 was already banned and I got the recommendation to re-fill with R413A, which had the benifit to retain the seals, which would have been necessary to be replaced in case of a change to R143A.
I was not overwhelmed with the cooling properties of the R413 in comparison to the old R12, but at least I got cool air back.
Then, a little while ago, the heater core started leaking and had to be replaced.
With that repair done, the heating was nice, but I did not get much cool air anymore.
It took until recently that I started to look for the problem and a solution...
I noticed (fairly easy if it had not been necessary to take apart half to the dash to get there) that the control cable from the temp-lever was not in contact with the "bypass valve vacuum switch" on top of the outlet of the heater core housing with the lever fully left="full cool".
I found this "screwing device" in line with the control cable, by which the length of the cable can be adjusted/fine-tuned, and I turned it until the switch was depressed with temp-lever in the "full cool"-position and until the lever started to move right. I assume that's the optimum cable length.
Result: I got my cool air back, as that switch stops hot water getting circled through the heater core and the vented air being cooled by the A/C instead.
That is the case when I have the A/C in its "max"-position, but when I shift the lever to the "A/C norm", the cool air dies down quickly...
There is a nice youtube-vid where a guy shows the replacement of vacuum lines in his 69 Corvette (https://www.youtube.com/watch?v=lqwHMvfeBSQ) and explaining how the vacuum operated vent doors should work.
With his explanations I was already able to check my car's "exterior air vent"-door at the plenum/wiper compartment. It is open (one can see the squirrel cage when looking behind that mesh screen in the wiper compartment, verifying the "open"-position) and/but it remains open with the car running and at whatever position of the vent lever. That guy says that at the "A/C max"-position this door should close together with the one in the passenger footwell opening to allow for a closed loop: passenger footwell->plenum->squirrel cage->interior of the car and back to start.
As both valves are operated on one and the same vacuum-source, I guess I should probably check next, if the pass footwell door opens at the "A/C max"-position... If yes, then the exterior air vent-door must be "stuck somehow", if not I have a leak somewhere in there...
But generally I was asking myself is: is there some troubleshoot-procedure that I can follow, or how shall I start with my investigations?
Thanks for your help and guidance.
Greetings from Germany
Oliver
As (here in Germany) I could not find anyone to replace the compressor front/shaft seal (which appeared to be the "simple" culprit), I had to have the R4-compressor replaced (which was not the original one, so not much grief). While at it, I also had the drier bottle replaced at the same time.
Unfortunately R12 was already banned and I got the recommendation to re-fill with R413A, which had the benifit to retain the seals, which would have been necessary to be replaced in case of a change to R143A.
I was not overwhelmed with the cooling properties of the R413 in comparison to the old R12, but at least I got cool air back.
Then, a little while ago, the heater core started leaking and had to be replaced.
With that repair done, the heating was nice, but I did not get much cool air anymore.
It took until recently that I started to look for the problem and a solution...
I noticed (fairly easy if it had not been necessary to take apart half to the dash to get there) that the control cable from the temp-lever was not in contact with the "bypass valve vacuum switch" on top of the outlet of the heater core housing with the lever fully left="full cool".
I found this "screwing device" in line with the control cable, by which the length of the cable can be adjusted/fine-tuned, and I turned it until the switch was depressed with temp-lever in the "full cool"-position and until the lever started to move right. I assume that's the optimum cable length.
Result: I got my cool air back, as that switch stops hot water getting circled through the heater core and the vented air being cooled by the A/C instead.
That is the case when I have the A/C in its "max"-position, but when I shift the lever to the "A/C norm", the cool air dies down quickly...
There is a nice youtube-vid where a guy shows the replacement of vacuum lines in his 69 Corvette (https://www.youtube.com/watch?v=lqwHMvfeBSQ) and explaining how the vacuum operated vent doors should work.
With his explanations I was already able to check my car's "exterior air vent"-door at the plenum/wiper compartment. It is open (one can see the squirrel cage when looking behind that mesh screen in the wiper compartment, verifying the "open"-position) and/but it remains open with the car running and at whatever position of the vent lever. That guy says that at the "A/C max"-position this door should close together with the one in the passenger footwell opening to allow for a closed loop: passenger footwell->plenum->squirrel cage->interior of the car and back to start.
As both valves are operated on one and the same vacuum-source, I guess I should probably check next, if the pass footwell door opens at the "A/C max"-position... If yes, then the exterior air vent-door must be "stuck somehow", if not I have a leak somewhere in there...
But generally I was asking myself is: is there some troubleshoot-procedure that I can follow, or how shall I start with my investigations?
Thanks for your help and guidance.
Greetings from Germany
Oliver