1994 4.0 HVAC problems

(A.J. Simpson) #1

I am in full springtime and the heater & AC are not working.

  1. With the key in the ACC accessory position and the fan set to the off position there is a constant rhythmic blowing every few seconds. This happens regardless of the position of the temp selector switch.
  2. This constant rhythmic blowing only occurs if the Fan Selector Switch is set to the off position.
  3. Unless the car is turned on and and at a sufficient operating temperature the Temperature Selector Knob is kind of irrelevant.
  4. With the car warmed and temp selector set to 85 calling for high heat the system is only producing uke warm air.
  5. With the car warmed and temp selector set to 65 calling for AC, at best the system is producing ambient temperature air.
  6. With the car turned on the voltage gauge shows a spike in voltage draw at every blowing interval with the fan selector set to the off position. If the lights are turned on they too will dim at every current draw interval

I don’t know where to start

(Gourgen) #2

it sounds like your blower control has failed which is part of the blower on xjs’s.

(Kirbert - author of the Book, former owner of an '83 XJ-S H.E.) #3


(A.J. Simpson) #4

Thanks for the starting point. I’ll report back after I dig into it.

I tried to post a video of the problem but there doesn’t seem to be any provision for doing so.

(A.J. Simpson) #5

After checking that all of fuses associated with the AC system were operable I switched out the relay on the fender wall. Removing the relay stopped the clicking that was trying to get the compressor to engage but satanic breathing that occurs every 5-10 inside the cabin never went away.

I pulled the climate control module from under the dash on the right side of the tunnel DAC10838 and swapped it for another CCM that I got from my 94 XJ40 parts car and the compressor stopped clicking and demon inside the cabin was exorcised.

The new symptoms from swapping out the CCM are the right side passenger face blower all but non existent and the system is producing hot air in regardless of temp setting.

This is the CCM that I pulled out of the car

This is the CCM that I swapped into the car from the XJ40

I don’t know how to test any of these CCM’s but it does seem as though there is a problem with the (AFAIK) original.

Where can I go to have it repaired?

(A.J. Simpson) #6

It seems the XJ40 CCM didn’t show up for some reason

(Kirbert - author of the Book, former owner of an '83 XJ-S H.E.) #7

First report I can recall of an issue with that CCM. I hope someone here can offer some help getting it fixed. Please keep us informed.