Eatc And Other A/c Mysteries

[cfkull]

I am having terrible problems with the automatic temperature control in my 90 SHO. I have been through 2 blend door actuators (one used, one new), 5 EATC control heads (3 soft button, 2 hard button), two ambient temperature sensors (resistance checked OK on both), two interior temperature sensors (resistance checked OK on both) one engine control computer and a complete under-dash wire harness and I still have the same problem. Self test on the EATC shows bad ambient sensor (-40 deg F), bad interior sensor (with some control heads, but not all of them), bad blend door (even though it has a brand new unit from Ford installed). We have run all of the EATC tests from the factory service manual and everything checks out, but the system still doesn't work and we are still getting the same error codes. We have run out of ideas and I cannot afford the rental car much longer while my only transportation car is all disassembled. Most of the system under the hood has been replaced by a company that does nothing but A/C work, so I am assuming it is OK. Compressor, condenser, both pressure switches, orifice tube all new or rebuilt items. Everything gets cold at the proper place. The problems all seem to be involving the EATC and sensors.

Does anyone have any useful ideas, or know of an A/C expert that I can contact directly?

 

[CerberuS]

Seen you replaced alot of things , but whats the actually issue? whats the eatc code giving you?

 

[jelloslug]

Have you check the alternator? The EATC is sensitive to low voltage situations and will react very erratically if the voltage goes too low.

 

[cfkull]

Error codes are 04 bad ambient sensor, 03 bad interior sensor, 02 bad blend door.

I do know about the alternator / voltage problems causing problems with the EATC, but at the moment we are getting 13.4 volts with the engine running, so I am assuming that is not contributing to my problem.

NEW INFORMATION - The ground to the control head is good, but the black/pink wire to the two sensors is not getting a ground OUT of the control head (or not going to ground through the control head, however you want to look at it.) If you apply an external ground at that wire everything starts to work correctly. At least that is something I can work on.

 

[jruppert]

pm sent