Hi everyone! I’ve read as much as possible about the Delanair MK2 that is installed on my late 86 4.2 Sovereign, but I didn’t understand where to start to diagnose what is the problem that leads to the behaviour specified in the title of the thread.
In order: during the overhaul I commissioned after purchasing the car, the professional changed the parts required for r134 conversion and charged the system. According to him, after the charge the car produced icy air and he was quite satisfied of the work.
The day after I came to the shop to check the state of the work, he wanted to show the miracle but the car produced no fresh air, rather a very hot one! I left the shop with the promise that he would check again the system, particularly checking for leaks and for vacuum-related problems. The same evening he called me telling that the system was discharged and recharged again and the loss of gas he found was not noticeable, so he excluded any major leaks. Furthermore, he told me that the system started to work again.
I retired the car last Friday, with 37 °C here in northern Italy; I put the right knob in auto mode but after a minute or so an extremely hot air started to come from all the vents.
This is what I can state:
The mechanical part is somehow working, the system switches from lateral vents to central vents and both
the blowers go to maximum speed, stop, go to low speed if the knob is put on LOW, so I suppose that they work
the heater valve is open for sure, I don’t know if the amplifier tries to close it, for what I understand this happens only when maximum cold is required
when I bought the car last October, I drove it home by night and the temperature was quite low: my impression was that in heating mode the system worked well, the interior was not overheated
I didn’t made the drop on idle test, now I’m at he beach with my son but tomorrow I will do the test in order to understand if the AC clutch engages.
Now, I would like to understand more about the correct diagnosis procedure in order to identify the problem and know better my car. In this phase my goal is to check as much as possible dismounting as less as possible. Please, correct me if I am wrong in the upcoming checklist.
First of all, I would start to check the left knob (a potentiometer?) to check the resistance values, and the same for the temperature sensor on the right; someone suggested to simulate an extremely high atmosphere with a lighter, makes sense?
Then I would check the heater valve; the professional told me it was ok and that could be a vacuum line problem, but I want to be sure that is functioning properly. Is there a procedure to check the functionality without dismounting? If I’m not wrong several parts of the system depend on vacuum, so if some flaps are moving can I assume that at least the vacuum reservoir is working?
I understand that if the system fails it gies into DEF mode, but is this the case? Hot air all the time but in AUTO mode air from all the vents and changing.
About the AC compressor, I tried to check the temperature on the intakes but all the area was so damn hot that I didn’t understand nothing, I just burned my left hand like a chicken
Finally I understand that the core of the system is the amplifier, is there a procedure to test it, like checking the signal that engages the AC clutch?
I excluded fuses because fuse-dependent components seem to function (right?).
Thanks in advance to everyone!