: A/C Question

08-28-07, 08:19 PM
Sorry to be a PITA, but I have a small question about the AC compressor...
I started to put some R134a in the high side, and the gauge hit 40 then the compressor kicked in and it dropped to 10. The compressor went off, the pressure rose again and the AC kicked in around 13 this time. Even though the gauge hit 40 psi when filing, when the AC came on, it dropped significantly.

Is it safe to add more R134, assuming that this is why the AC wasn't kicking in at all when I got the car, or is the rise and fall of pressure something else?

I have to put my hand up here and say I grew up where cars didn't have AC. They had lots of other gadgets, but no AC.

Thanks for your help everyone

08-28-07, 09:33 PM
I am sure that you did not add it to the high side. The high side fitting is a different size to prevent you from doing that because the can would become a hand grenade.:bomb: Rising and falling pressures are normal as the compressor engages and disengages. Those pressures are not. How much is in there now?

08-29-07, 05:06 AM
LOL!! I meant the "low" side ;)

Now, the pressure is around pounds when I put a gauge on it...it's just that when I pull the trigger to add the 134 it rises to 40 before the compressor kicks.
When the compressor clutch engages it's 13.

08-29-07, 05:08 AM
around 13 pounds until I try to add more, the squezing the trigger makes it go as high as 40 till the compressor clutch engages.


08-29-07, 10:26 AM
Might be a bad compressor. Pressures should rise when the compressor engages.

08-29-07, 01:05 PM
When the system is at rest the pressure is the same throughout. When the compressor is turned on (clutch engages) the low side drops and the high side rises. When it stops the pressure equalizes.

Your pressures sound normal for a very low charge. It should be somewhere over 100psi at rest. Going to 30 low and 200 high (rough estimates).

Look around at some of the AC websites. They give a nice explanation of how AC works, which is really pretty simple. (It's all simple when you understand it!:))

08-31-07, 09:56 AM
Thanks. The AC kicked in eventually after adding more but the clutch burned up, so it's AC replacement time I guess. Not the end of the world.

08-31-07, 11:53 AM
If the compressor is OK, the clutch is serviceable separately.

08-31-07, 12:26 PM
If the compressor is OK, the clutch is serviceable separately.

Right! and you shouldn't lose the charge just changing the clutch.

08-31-07, 01:03 PM
The shop says that the compressor/clutch and receiver/drier need to be replaced $275 parts cost. I checked online and $230 seems to be the lowest I can find the parts for, so doesn't sound too outlandish?

08-31-07, 09:23 PM
That actually seems too cheap for those parts. A/C Delco?