Air Conditioning troubleshooting
 

Good morning, with summer fast approaching I have been working to get the A/C stystem up and running. Working through everything I noticed the heater return line from the heater core was getting as hot as the feed line. Replaced the water valve thinking this was the issue. Currently still does the same thing? Has good vacume with the A/C system is on? Is this correct? With the A/C system off the vacume stops. First roadblock of many to come.

Re: Air Conditioning troubleshooting
 

The valve is the most likely suspect. Vacuum should close the valve with the AC on. If just a little hot water leaks past, it will cause the heater core to fight the AC. Swapping the valve out is an easy fix.

Re: Air Conditioning troubleshooting
 

That's the thing, I swapped out the valve with a new one with same results. Tomorrow heading after the vacuum system to check for a small leak or possible restriction.

Re: Air Conditioning troubleshooting
 

Mine did the same thing, even with a new hot water valve. I ended up splicing a gate valve into the hose to completely stop the flow of hot water. With the valve closed, the hose stays cool.

Re: Air Conditioning troubleshooting
 

Replaced all A/C vacuum lines, found come crud inside lines, but still have the same issue. Also found out inside passenger kick pad valve won't open alone. If I assist it will hold open until shutdown or change to outside air. Plenum valve works great?

Re: Air Conditioning troubleshooting
 

Check the vacum head on back of the controller. There are several diferant ones. You may have the wrong one on it. Best thing is do as stated above. Put you a manual cut off valve in line with the vacum valve. This way you have no heat coming into the truck cab. Mine works great. :chevy:

Re: Air Conditioning troubleshooting
 

I wanted to replace the vacuum control switch but this seems to be a needle in the hay stack? Anyone have an idea who has this part? Got this pic from an older post.

Re: Air Conditioning troubleshooting
 

Try removing the vacuum hose, and if that works then you probably have the wrong water valve. WAG.