Eatc ??

[MADRODER]

So I've spent a good chunk of my morning researching MM.net looking for fix for the Marauders heating / cooling issues, I know the HVAC system defaults to DEF / FLOOR when there's a problem. I do not hear the door opening and closing when I switch to different zones so is it the EATC ring issue as many here say it is ?? and it will get warm eventually ( 10-15 mins when temps outside are 32 F ) Here's what I've done so far....

Ran the self -check.......no codes
Checked for vac leaks.......cant hear anything

[MyO4Rawdur]

The o rings are such a simple repair that id just do that anyway. Ill see if I can find the thread

[RF Overlord]

The usual symptom of bad EATC o-rings is normal operation until the gas pedal is depressed to go up a hill (for instance) which causes the system to switch to defrost-only, then back to the initial setting once you let up on the gas.

When the throttle is depressed, manifold vacuum is reduced and the vacuum reservoir (black box on top of the driver's wheel well) takes over. If the o-rings are bad, there's only enough vacuum in reserve to hold the various doors at the desired settings for a short time. When the throttle is released, manifold vacuum returns and the HVAC once again operates normally.

If yours is stuck on defrost only, then either the EATC head unit is bad, or you have no vacuum at all going to it. There's a check valve in the line that has been known to go bad...I believe it's in the engine bay just before the line goes through the firewall. Or try removing the EATC head unit and seeing if you have vacuum at the harness connector port with the black hose.

[fastblackmerc]

So I've spent a good chunk of my morning researching MM.net looking for fix for the Marauders heating / cooling issues, I know the HVAC system defaults to DEF / FLOOR when there's a problem. I do not hear the door opening and closing when I switch to different zones so is it the EATC ring issue as many here say it is ?? and it will get warm eventually ( 10-15 mins when temps outside are 32 F ) Here's what I've done so far....

Ran the self -check.......no codes
Checked for vac leaks.......cant hear anything

The most common symptom of bad o-rings is the air always comes out the defrost vents. If the o-rings are bad you wont hear a vacuum leak.

Since you don't hear any doors opening or closing there most likely bad o-rings in the EATC.

I can replace the o-rings for you. PM me.