I have an 87 and the heat is on full.
The clips on the servos are all good, the heater valve is brand new.
I followed the Service manual and checked all 3 sensors all 3 register the correct Resistance.
I have replaced the main controls with a known good one.

Nothing is fixing this? Does anyone have any suggestion on how or what I need to test next?

Thanks

 

The is a procedure HVAC-01 @
http://www.clarks-garage.com/
that may help you
Keith

 

Yes followed and as stated the clip is good, the heater valve is good and the control unit is changed.
All 3 of the items stated in Clarks garage, and per the service manual all 3 sensors have been tested as well.

 

I've noticed on somethings, not necessarily my car, but even though electrical things check out fine, doesn't always mean that they are working correctly. Just an idea.

 

Have you checked the HVAC vaccum lines

 

Have you verified the HCV is actually working? For example, when starting the car cold, you should see it close in the first few seconds of start-up, and it shouldn't open until the engine has warmed up.

 

I know it's good because it's brand new and tested, but NO it doesn't close because it has no vacuum. The service manual doesn't show or say how to test the vacuum motors or what triggers them. I was hoping someone on here might know how to test or where to look on what turns them on.

Thanks

 

There is some information on heater malfunction @
http://www.clarks-garage.com/
Good luck

 

Are you sure vacuum is getting to the CC head?

 

Heater control valve linkage (under the bonnet) can snag on the vacuum line.

Mike

 

If you knew the HCV wasn't closing, why didn't you just say so? What's all this other irrelevant stuff?

 

How is knowing what has been checked irrelevent?

The HCV is brand new, not closing means no vacuum, since the service manual doesn't explain what triggers the vacuum servo I had hoped someone on the board might know something that might be able to help me. So why not explain what I have checked in hopes someone has a decent answer. I am sorry my question is irrelevant.

 

I think all Mark s trying to say is the question should have been " I have a brand new HCV and it is still not closing, I am assuming no vacuium , can anyone help ? "

Might have been a a better place to start is all ....

 

On my 1987 944 NA there is a vacuum line inside the engine compartment connected to check valve on the brake booster. It runs across the back of the engine on the firewall to a rubber tee. One of the tee outputs connects to the HVAC vacuum canister on top of the fire wall under the black plastic cowl on the passengers side
The 2nd tee output runs down the fire wall to a rubber elbow and thru the the firewall into the HVAC assembly. There is a 2nd vacuum line in the same location which runs from the fire wall to the heater control valve on the back of the engine block. The two fire wall vacuum lines are just above the heater hoses where they run thru the firewall to the HVAC assembly. I disconnected the the small check valve at the brake booster leaving the check valve connected to the HVAC vacuum line. I connected a hand operated vacuum pump/gage to the check valve and pumped vacuum on the HVAC system it holds vacuum. If you could try this you might find a vacuum leak.
Hope this helps
Keith

 

Unfortunately there is no info on the operation of the heat/ac control unit. I suspect many have the same problem. When the ac and heat control valve are working properly you will hear the solenoid that controls the heat valve clicking occasionally. I suspect you have a faulty control unit, even if you replaced it. You can however bypass the solenoid that controls the hv running vacuum to it always. Doing this also eliminates heat needed for defrost. I did this during the summer and had no problems.