Last time I drove the truck any distance (In September) I had A/C, with the E-Fan (POS Taurus fan) hi-speed connected I did not. Just to ensure I had proper cooling for when A/C was in use I spliced into the A/C clutch relay, Pin 87.

Now that winter has taken over I started the ol rust bucket up again. Noticed on Def I had foggy door glass, so I checked out the clutch this weekend. It's not operating when the A/C or Def is selected. I still have the low and hi pressure circuits to check, but it only reached 16 today and I gave up after testing the Relay to Clutch and removing any E-fan wiring.

I can't find enough info in the service manual, to tell me if the hi/lo pressure switches play a role in the A/C sense circuit.

Anyone know? Any way to test the PCM other than at the stealership?


TIA.

Brian

 

Dude, it has nothing to do with the pcm, the evap core is probably bad and you have no r134a in the system anymore.

 

It's possible. But working with out an issue for two years, wouldn't there have been intermittent operation at some point?

I'll check the low pressure switch in the morning I think we do for a warm up to almost 20. Found some testing points to check. No refridgerant, no continuity, open circuit no relay trigger.

I feel a trip to MI, MN or IL coming up if I'm out of refridgerant since WI won't sell it to me.

 

You can put a jumper on the low side switch (momentarily)and see if the compressor starts.

 

yeah, found that. Should also see continuity across the switch if there is refridgerant present.

Was reading more in the service manual. Says that at temps below 30f the clutch will not operate since the low side switch will be open. I'm not losing my mind, the 98's (the rest of the 2nd gens) did run the A/C when defrost was on, or does it just draw in outside air?

 

You are right, the compressor will cycle when the heat/defrost is on. It helps with condensation on the windshield and keeps the system oiled(so to speak).

 

Ok, compressor works when low side pressure plug is jumped. I'm getting nothing across the switch contacts. But then I'm not getting anything across the switch on the Van that works. Is there a defrost Over-ride circuit that I'm not finding?

Back to the service manual.

thanks.

 

With your vent control set to defrost, the compressor SHOULD cycle. Can you check your pressures?

 

I'll check HF and see if they carry the Low side gauge in WI..otherwise I'll wait till next month and take it to a shop and have it checked.

Not a huge deal...once I start getting some heat (which sucks, but it's too stinking cold to go back flush the core, will end up with ice all over my dw) it will keep the windshield and side windows clear, and even during WI summers I don't often use the A/C, but the wife becomes down right pissy.

Wish I could find more info on how A/C circuit functions with the Defrost. Since the low side switch opens at temps below 30f what is the override when in Defrost mode? Any codes? BTW...the 3 on key trick does nothing, nor does holding down the trip reset. Any other tricks besides the readers?

 

I wasn't aware the switch even cared about temp. I haven't ever seen mention of that anywhere..... but, there it is, right in the FSM. neat, learn something new every day.

I think it is a function of what ambient temp does to pressure though...... it is probably working exactly as it should.