Help all.

I have had the eatc in my truck for a while. When my eatc is on auto it will blow out the vents for a few minutes then switch to defrosters and back to vents and defrosters and so on and so forth. I ran a diagnostic and didn't get any codes. Can anyone help me resolve this problem. Please help.

 

Small vacuum leak.


If you stop on the gas does it switch to defroster?

 

No it does it at random.

 

It still blows AC it just blows it out the defrosters and then vents yadda yadda yadda

 

When the system loses vacuum it defaults to the defroster.

I think you have a leak or lose hose. I'm not sure if the EATC can do this tho.

 

Vacuum leak where? Any other ideas I don't hear any hissing from a leak under the hood. Anyone please.

 

A vacuum reservoir used for the HVAC stuff under the air box in the fender. It has a one way check valve to keep vacuum when you accelerate. The reservoir can get damaged from road debris as well as the lines to it.

Pull the res out and check everything connected to it.

 

If the reservoir you are referring to is that black plastic ball. I checked it and found no damage and no apparent leaks during engine operation. Also I checked the lines coming out of that ball and the check valve on the upper line and found no damage or leaks during engine operation there as well. This has been an issue since I installed the EATC just miserable during summer. Any other ideas?

 

Have you checked the vacuum harness for the EATC?


My last resort is to swap the vacuum controls back to the stocker and see if the problem is still there. It will rule out the EATC valve block.

 

the green hoses in back of EATC unit look fine. Could it be a sensor?

 

if I just re-attach the original manual ***** will it work? Is that what you are talking about? How do I do that after re-wiring everything for eatc. I would like to keep eatc. I just need it to work right.

 

I was suggesting changing the vacuum portion only for testing.

You would need to set the eatc and the ****.

If it works like that, your EATC maybe bad. IF its still flaky then your issue is somewhere else.

 

Oh ok so put only the vacuum lines to the old ***** and leave the rest on eatc for testing?

 

Yeah, see if it works like that. Its not a fix but it may work like that.

 

Well looks like you were right about the acceleration thing. Funny that I never noticed that was the cause before. Anyway on the way to work today I watched when it happened and it happened every time I accelerated either from a stop or from low speed say 15 to say 45 and stayed on defroster till I had let off of the gas. Gotta remove the EATC this weekend and see if I can find a leak on vacuum harnes in dash. Quick question though. The little vent on the right of the dash. I wired it but never ran the hose all the way down to the flipper box cause I didn't have enough hose and can't find more. Is that a possible cause and is that necessary to have that hose ported into that box?

 

Thats the inside air temp sensor right? If you want the eatc to keep the temp selected i think you need that hose hooked up.

The defroster is a loss of vacuum issue. Start at one end and work back to the other.

 

Ok I will troubleshoot the vacuum issue this weekend after I go fishing saturday:) Any ideas on where I can get some more of that white tubing for that sensor? I have tried e-bay, auto shops, parts stores with no solution.

 

Rockauto used to carry the sensor with the tube but I don't see it listed anymore.

I only checked on a 2000 maybe they have it listed in another year.


Beyond that figure out the diameter and find a hose that will work. Try http://www.mcmaster.com/ under duct hose.

 

Ok so I just got done troubleshooting the whole thing. Here's the deal, all vacuum lines and reservoir are good. HOWEVER when I plugged the manual/stock vacuum in and took it for a test drive it worked fine. Does this pretty much mean that my valve block and/or eatc box are bad. I took it apart and the valve block looked fine and no wires were bad or anything. Need help.