86 NA 944, When the blower is on it will only blow hot air even though the potentiometer is set to cold?

 

Couple of things. Make sure the vacuum line from the heater control valve on the backside of the engine is connected at both the firewall, and at the valve itself. it is hard to see the firewall end, but there is a 90 degree connector that should be plugged into the firewall.

Next is a small plastic clip on the side of the heater control unit itself that likes to break. It is found down in the drivers footwell. It is about a $2 clip.

 

Speaking of heaters, mine was working fine until I decelerated from a fast rate of speed and then it went cold? I'm thinking that the engine rpm (waterpump-waterflow...) may have finally causes the heater control valve to quit working? Ideas?

 

Make sure you coolant is topped off and there isn't an airbubble in the system. Then check all your vacuum line connections.

 

I have the same problem on my 89 N/A. Only my fan also wouldn't stop blowing.I found that a small vacuume valve was hanging off one end of a vacuume hose with it's tip stuck in the other hose. I took it out and connected the hoses to each other. It didn't make anytihng better so I jsut took out my fan relay so it doesn't blow the hot air all over.

 

Vacuum doesn't have anything to do with fan speed. Check your fan switch resistors.

 

does the compressor affects the hot air too? compressor together with filters? any ideas?

 

A/C compressor? No it does not affect the heating system.