heater coil energized

I have a 90 Dodge caravan with a 3.3liter engine.The a/c was not functioning so I checked the r134a charge{40 psi on the suction side}, so I cleaned the condensor coil and checked the radiator fuild.I then noticed with my temp probe that the air coming from the vent was 35 degrees hotter than ambient.I checked the heater and found that the coil is 165 degrees so the air mix temp is too hot to cool the car.I am a HVAC tech and know little about how to disconnect the heat or if I am missing something.Any help would be appreciated

 

There are no heater coils in auto's that I know. Heat is produced by the hot coolant running into the heater core, which is basically small radiator. It cannot be shut off unless you bypass the coolant lines. If you are getting hot air out the vents, then you might have a blend door or control panel problem.

Feel the AC lines going into the firewall, one should be hot, the other cool and wet. If they are both hot, then you have a problem with the compressor or elsewhere within the engine bay.

 

Awrighty now!!!!........When you say 40 psi on the low side .what was the high side reading?????..........THAT particular system will throw the high side close to 300 psi before the coolant fans kick in.........Once the fans kick and the system stabilizes the readings should be approx 225/45.........But they CAN read that with a charge low enough that the fans don't come on.......
These vehicles are NOTORIOUS for forward evaporator leaks ......
If you find that the blend air door is in fact the problem.........A general hardware store should be able to come up with a manual shut off valve you can install in the heater line............Turn it off in the summer and back on in the winter...........
Don't remember the exact reason ............but we installed a TON of them in Chevettes for just that purpose.......

 

sorry about the terminology...I work on chillers and large ton equiptment.I checked the high side pressure 230 psi and both condensor fans are on(located in back of the radiator right).so my last question would be should the heater core always be hot?And where would I place the ball valve as one response suggested.I live in an area where no one works on mvac,we hvac guys try to do what we can but this one is kicking our butts.

Thanks for the help!! Love the qoute!!

 

Yes, this heater core is always hot. This heater core is within your airbox under the dash. A blend door opens/closes to allow the heat off the core to enter the blower fan assembly, and into your vents.

Seeing this is a 90, your blend door might be vacuumed controlled. Look for any leaking vacuum lines under the dash and/or in the engine bay.