Another AC Recharge Question
 

Just had my AC recharged with 134a after replacing all hoses with new barrier hoses and installing underbelly static condenser.

Questions: After running AC for about 20 minutes the compresser seems hotter than usual. Could I be low on compressor oil. The AC guy said he added oil but perhaps not enough.

Can I add oil without loosing freon?
How do I know when there is enough oil?

Lastly, with the static condenser and no rear deck condenser, how many lbs of 134a should be added to the system? He charged it with 2.5 lbs.

As always, thanks for all the help I get from everyone on the BB.

Guy Chiattello
1882SC

Re: Another AC Recharge Question
 

You can add oil without loosing freon. They have on the market a can with oil that look similar to the small freon can and in fact the can also has freon.

You don't want to add to much oil since oil is a liquid and liquid if you remember you physic can not be compressed.

I suspect your problem is inadequate air flow over the condenser; if I recall correctly you no longer have a rear condenser. With this type of set up your high side pressure and temperature will rise (and hence compressor temperature will rise) when the car is not moving; are you getting these high temperatures while the car is idling or moving slowly? 2.5 lbs sounds like a little too much to me; one really has to charge these R-134a systems using pressure gages with air flowing over the condenser (how was this done with your set-up?); excessive charge will lower performance. You did install an over pressure cutout switch? Cheers, Jim

Jim,

Thanks for the response. I do have a high pressure cutoff installed. I don't believe the AC guy ran air over the static condenser when he recharged the system. I'll get a pressure gauge and run air over the condenser with a shop vac or fan. to see what kind of pressure I'm getting. Would it make sense to release some of the 134a?

Guy Chiattello

It's against the EPA's regulation to knowing release freon from a mv system.

Why don't you bring it back to the shop that charge the system and ask them to recover the freon.

go to this forum for a/c questions

http://www.ackits.com/forum/index.cfm

Again are you getting these high compressor temperatures while idling or moving slowly? Your set up will not ever work well under these conditions; you have to keep your car moving for the under belly condenser to get cooling air.

for 134a, approximate values:

Low side:
16 to 29 psi for 33 to 50 deg F evap temp
19 to 39 psi for 33 to 60 deg F evap temp
25 to 43 psi for 40 to 65 deg F evap temp
37 to 51 psi for 48 to 65 deg F evap temp

High Side:
115 to 200 psi for 70 to 80 deg F ambient temp*
140 to 235 psi for 80 to 90 deg F ambient temp*
165 to 270 psi for 90 to 100 deg F ambient temp*
210 to 310 psi for 100 to 110 deg F ambient temp*

*temperature of air moving over condenser usually measured two inches in "front" (front is side receiving air first) of condenser.

If the pressures you measure are too high and you have air moving over the condenser while you are measuring pressures then you will likely benefit from less refrigerant.

Now I need to go run some new A/C hoses on my '76:D .

Cheers, Jim