Ac Troubleshooting

[RogerDodger]

Went to turn on the ac today and the compressor is not kicking in. The blower comes on for all the different functions. Defrost, AC, Max AC... I have 13+ volts at the drier/receiver but no voltage continuing to the compressor. Any help is appreciated.

[AZMoparboy]

Hi, I just went though a little AC trouble of my own. I would hook up my service manifold gauges and see if you have  enough coolant in the system to activate the pressure switch that you were checking for continuity.  If you have very little to no pressure in the system then the compressor will not turn on via the pressure switch.  The next step would be to find out where the leak is in the system If there is a low coolant problem.

AZMoparboy

[RogerDodger]

Good advice. It was just barely low and a quick shot the compressor kicked in. Still not very cold but I think thats what you get with 45 year old technology. Thanks for the help.

[Pete in NH]

Hi,

The low pressure cut out switch will close with only about 40 pounds of pressure in the system. That is far too little refrigerant to get any real cooling. It sounds like there is likely a leak in the system that needs to be found and repaired. Once that is done you can vacuum down the system and recharge with the factory specified amount of refrigerant if it's a stock system and R-12. If  the system is stock and has been converted to R-134A you would charge 70 to 80% of the factory specified charge. A factory stock system will freeze you right out of the car if working properly. Don't discount that 45 year-old technology. Those systems were over designed in ways no modern system even comes close to.

[RogerDodger]

Thanks for the heads up Pete. Sounds like I may not have properly vacuumed the system prior to charging it. Thats why I'm not as cold as it should be. I'll get some help with that and the leak isolated. Is the draw on the motor normal? I have to adjust my idle a good bit higher in the summer if I'm going to run the ac. Seems pretty extreme. Almost enough to not want to use the ac.

[Pete in NH]

my 71 383 picks up the A/C load without any noticeable fuss. I've never had to readjust the idle speed.

You want to vacuum the system down to below 28 inches of vacuum and let the vacuum pump run a while to get out as much water vapor as possible. I usually let the pump run 2 to 3 hours. Send me a PM and I'll send you a set of charging instructions if you need them.

[John_Kunkel]

A factory stock system will freeze you right out of the car if working properly.

You maybe, but not me.