Hi Everyone,
I know this may have been covered numerous times, but I am struggling to understand why the system wont run continuously. My A/C will work on defrost but only occasionally works on low, auto, high. I have studied the diagrams and need help. I have Freon because it's cold from the defrost vents. Although low is a possibility. Would that prevent normal operation? I have checked vacuum, it is good. Both fans motors function, and the system will operate normally on occasion, as I said. Usually I turn on the system and nothing happens. It is the Delanair MarkII system.
Any suggestions would be great.
Thank you all.
Cheers,
Brent
Martinez, Ca

 

I suspect the amplifier is on the blink....only because it is the most common culprit. But the fault could be elsewhere. Diagnosing the system is tricky....especially if the amplifier itself is not positively know to be 'good'.

When you select 'auto' and dial in maximum cooling on the temp control, do you hear a faint humming sound behind the dash? You should. That's the servo trying to change the flap settings in response to commands from the amplifier.

If no humming the servo is dead.....or isn't being commanded by the amplifier due to an upstream problem...possibly the amplifier.

Have you checked all four system fuses, by the way?

You can divorce the servo from the servo from the amplifier in run it (the servo) thru the full hot-to-cold range using jump wires. This way you can tell if everything downstream of the servo is ok.....and then focus the servo and everything upstream of it

Try to find the "Delanair Mk II Training Manual". Google it. They pop up every so often. Very very useful guide.

Cheers
DD

 

Thanks Doug,
I do have the training manual. It is informative and a challenge to decipher.
I think I have multiple problems. The car sat for a few years and has undergone a recent restoration and upgrade of many parts. I suspect the amp is the culprit as on occasion it will select new temps by the servo. I found no hot water getting in to the matrix despite a new heater valve. This then must be the amp, servo, or another vacuum check valve, stuck. So the temp switch never gets heat, so the system won't energize. Shorting across the temp switch proves that. I wish there was a replacement amplifier. I could rig a double pole switch to select temps, but where to put such ugly thing. I sent a message to JagSpares in Aust. I asked if they have or had schematics on their no longer available amp.
In the mean time I will try to clean up right side linkage and vacuum valves in hopes of getting the hot water to flow. I am using Evans waterless coolant, by the way. So nice to eliminate corrosion from my new system.
Thanks again for your suggestions and response.
Brent