Hi this is my first post. I just joined cuz i am completely stumped with my ac. I have a 99 blazer with no major mods and a little over a 100,000 miles. I just bought it this winter and the ac has never worked. My friend tried to recharge the system but it wouldn't take any refrigerant. The compressor does not turn on when you turn the ac on. all fuses appear to be fine and you can move the compressor by hand. then we ran wires directly from the battery to the compressor and it kicked on. so i think i have an electrical problem but i'm not sure. i also heard about a safety switch that doesn't allow you to refill the coolant if it is too low?? any ideas or suggestions would be greatly appreciated. thanks.

ryan

 

To recharge a system, you need to have the compressor running. So if you did not have the compressor running while attempting to recharge the system, you'll need to jumper it as you did before and try the recharge again.

Now if, when you jumper the compressor with the hvac controls set to cool inside, you get cold air out of the vents, then you may have either a cycling switch or low pressure switch failure, but you need to get the refridgerant level up to par before looking into the sensors.

 

how do you jump off compressor?

 

You can manually engage the compressor clutch by supplying it with a ground and +12V on the appropriate terminals at the clutch connection on the compressor.

After manually engaging the clutch, you should have one line getting cold. If this happens, then you may be a bit low on freon, or the low side pressure switch may be bad.

If after manually engaging the clutch, the lines off the compressor don't get cold, then you are most likely low on refridgerant. If that is the case, then there are two possibilities...

#1 - You have a slow leak and a top off will bring it back to the appropriate pressure.
#2 - You have a rather large leak and topping the system off will only temporarily cure the problem.

In both cases, a R134A recharge kit from your local autoparts store and possibly some extra cans of R134A refridgerant will bring you back up to the appropriate pressure. These kits also have leak detector in them (a flourescent dye) so if you do have a leak, you have a means of finding it's location and fixing it appropriately. If you find yourself recharging your system every year, you have a problem. To keep on dumping refridgerant into the system year after year is bad for the environment. In the long run, it would be better to fix the system correctly than to keep bandaiding it. Sooner or later there will be a much higher repair cost as the components break down from contamination in the system.