1993 T&C Van - A/C wiring question - annoying problem

Hi. If you have any ideas or experience in the 1993 T&C A/C
I would sure like to read reply. It will help me keep cool.

I am having an annoying intermittent problem with the A/C system.
Sometimes I will set activate the A/C button on the
dash but the A/C compressor will not come on for about 2 minutes,
or even longer. Usually the radiator fan does not come on either.
After a while the A/C turns on and the cabin gets real cold.
A/C charge is OK, low side 25 PSI, high side 175 PSI.
I am pretty sure it is not low R-134a because the pressures seem
just about right and when the A/C turns on it gets delightfully
cold. Must be something electrical.
Since the radiator fan doesn't start when the compressor is off
I am assuming the problem is either the computer or one of the
sensors sending bad readings. I assume the compressor clutch is OK.
I first want to test the sensors and/or wiring before I blame
the computer.

So HOW DO I TEST THE SENSORS?
Anybody got a good wiring diagram I can use?
All I can find are two sensors.

One is attached to the high-side distribution block mounted on the
firewall. I'm assuming that is the high pressure cutoff.
What should the normal resistance be? low or high?
Is there any way I can hot-wire it to see if that's the problem.

The other sensor is attached to the hose near the lower front
by the radiator. It is attached near the accumulator/dryer.
Here too, what should the normal resistance be? low or high?
Is there any way I can hot-wire it to see if that's the problem.
If I remove these sensors, will there be a R134-a leak, or are these
attached to Schrader valves to prevent total loss of R134-a?

Any thoughts in hot-wiring the compressor? Good or Bad.

Finally - I think I need to add some A/C oil. All I can find is
'ester oil'. I don't know what is in the system now, maybe ester and
maybe PAG. Is ester oil compatible with PAG? What are the drawbacks
if the current oil is PAG and I add ester? Opinions please.

HELP - It is getting hot here in Georgia.
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Those pressures seem a little low. Check your sight glass (under the jack).
Does the compressor cycle alot? It should cycle very little. My 93 when it
was spot on would run more like 240-270 high and 35-55 low FWIW.
Larry

 

I've got a 1993 Dodge Grand Caravan and my compressor has always cycled
often. Even after being charged. I asked an A/C person if this was normal
and he said some compressors were designed to do this. If this is not right
or normal, is there a switch or relay that I should replace ?

Thanks,
Nick