1998 Dodge Caravan HVAC

VMACKELL

MEMBER
1998 DODGE CARAVAN
6 CYL
2WD
AUTOMATIC
259,000 MILES

My ac wont turn on when you push the ac button, relay does not activate, I can activate the relay manually and when held activated the ac will start the compressor and cool the car,
Have run the calibration/diagnostic test and after reseting the initial error it passes
When I run the cooldown test it obviusly fails as the ac does not start and the ac and recirc light flash.
My question, is the HVAC control module bad, or is there some other way of reseting the unit?
I already donated and all I was told was to run the diagnostic test.
Vincet

1 Reply

CARADIODOC

MECHANIC
33,879 POSTS

The cool-down test only calibrates the in-dash temperature sensor. The AC will still run if this test fails which it usually did on '96 and '97 vans. It's not uncommon for those vans to take 20 or more attempts to pass the test. By '98, I think they had the bugs worked out and the test would pass easier.

Most people don't know how to bypass a relay. Since you do, have a second person watch in the sight glass on the receiver / drier to see if there are any bubbles present when the compressor is running. Bubbles mean the system is low on charge. The relay should turn on if you jump the wires in the connector to the low-pressure-cutout switch. Even though it's low on charge, it still might cool ok.

If it's not low on charge, try swapping the relay with another one on the unlikely chance the relay's coil is open. I would more likely suspect a defective HVAC computer.

Caradiodoc