Automotive Air Conditioning Information Forum

This non-working ac system is bothering me so I had to go outside and do yet another test. Those low H pressures that I got earlier today are not consistent with the higher H pressures I saw 3 days ago.

Ambient temp had increased to 90F. I restarted the car and the radiator fans running on low.

Idle-----------------1500rpm
H210----------------H210 rising to 240
L30------------------L25
vent 93F------------92F

I did a second idle and 1500rpm test and the pressures were a little lower on the L side and the vent was 90F



I then turned the ac OFF and then back on to MAX and now the H pressures went way up. More like what I saw 3 days ago.

Idle------------------1500rpm
H320----------------400
L24------------------24
vent 82F------------82F

Last test:

Idle------------------1500rpm
H350-----------------400
L25-------------------25
vent 77F-------------77F


Notice that the vent temps did inch down. The driver's door was open so the cabin of the car wasn't really getting cooler and the blower fan was on high for all tests that I've posted. There was plenty of water condensation dripping out of the bottom of the car. I did look closely at the water with my UV light and saw no dye.

These varying High pressures have me baffled. There is no obstruction in front of the condenser and the two fans are running on high speed when the High pressures are up higher.

18 year old electric fans. You are chasing your tail.

Spray the condenser with water and watch the pressures. You should be able to get the system to stabilize at the control valve pressure on the low side - if you can get rid of the heat.

We went through this at length on the old board. The electric fan may be running at "high" as far as the pcm is concerned, but the tired fan motor can't cope with the heat load.

Clean the heat exchanger stack too. While the face of the condenser may look clean, it can have plenty of bugs & debris deep in the fins. Avoid high pressure washers, just use a good surfactant like Simple Green sprayed in to the fins of a cold condenser. Let is soak for a few minutes, and flush it out with a garden hose. You may be surprised at what comes out.

bohica, thank you for your information as well. When my electric fans were running on high, I was able to get my hand behind the passenger side fan and confirm that it was pulling a lot of air. I wasn't able to get my hand in a good position to confirm that the driver's side fan was pulling the same amount of air.

Over the course of the next week, I'm going to disassemble the whole "cold air intake" system sitting right above the radiator so that I can get to the top of the radiator and condenser. I'm going to visually confirm that there is no debris between the two. I'll clean it all up just to be sure. While I've got things apart, I'll try to figure out whether or not those two electric fans are working at 100%.

On Wednesday, I sprayed down the condenser with water and the H side pressure dropped a lot. I posted those numbers in post #10 (2 Sep 20 @4:12pm.)

Earlier in this thread I had mentioned a Robinair RG3 recovery machine. In addition to the Trans Am that I'm currently working on, I have two project cars in the garage that will need ac work. My wife suggests that I just buy the recovery equipment and be able to do what I need to do when I need to do it. Unless you guys tell me not to buy my own equipment, I think that I'm going to add this machine to my tool collection .

I have a question on recovery whether I do it myself or if I paid the shop $100 to do it. Doesn't some oil come out of the ac system along with the refrigerant? If so, wouldn't that affect my scale's weight reading? How would I know how much oil to add back into the system?

So it sounds like only 1/2-1 oz of oil would come out of my Trans Am's ac system during a refrigerant recovery. According to Rock Auto, my car should have PAG150 type oil.

Unfortunately, the little Robinair RG3 doesn't come with an oil separator so I would have to just guess on how much PAG150 to add back in.

Here is the Robinair RG3 that I was thinking about buying:

https://www.robinair.com/products/rg3-p ... ry-machine

Sorry Danny.

After a19 starts clogging up a thread with useless junk I just scroll to the end - where I see pressures as high as 400 psi. I missed the part where you sprayed the condenser.

You say the fan blows well. But what is well? is it 75% of what it did when brand new? The only metric we have for older cars fans is current draw and cooling. With worn brushes, current drops and air flow drops. We chased this on the old board, it went about 8 pages with a Ford Edge I believe. New fan brought the high side down to the proper range.

I am NOT saying that the fan motors are bad - other things like clogged fins & debris in the heat exchanger stack can cause the same issue. As can missing air dams and seals - if the fans are pulling air from the edges of the stack, the air bypasses the condenser.

Once you get the proper charge level in the system, and are sure your heat exchanger air path is clean & clear, you can further evaluate the condition of the fan motors.

That machine you posted does not reclaim. It is only for recovery. You would have to use new refrigerant if you used that machine. And as mentioned, it does not separate refrigerant from oil.

bohica2xo wrote:Sorry Danny.

After a19 starts clogging up a thread with useless junk I just scroll to the end - where I see pressures as high as 400 psi. I missed the part where you sprayed the condenser.

You say the fan blows well. But what is well? is it 75% of what it did when brand new? The only metric we have for older cars fans is current draw and cooling. With worn brushes, current drops and air flow drops. We chased this on the old board, it went about 8 pages with a Ford Edge I believe. New fan brought the high side down to the proper range.

I am NOT saying that the fan motors are bad - other things like clogged fins & debris in the heat exchanger stack can cause the same issue. As can missing air dams and seals - if the fans are pulling air from the edges of the stack, the air bypasses the condenser.

Once you get the proper charge level in the system, and are sure your heat exchanger air path is clean & clear, you can further evaluate the condition of the fan motors.

bohica, the only thing that I have to "tell" me that the fan(s) were running on high is the change in sound when they were commanded to go to high. The sound might have only come from one fan. I assumed both but I really don't know for sure at this point. Can you elaborate on the method to measure current draw? I'm not real good with electrical stuff and I'm pretty sure my DOV meter is only good for 10amps.

I'll look extra close for loss of air dams and seals. I spent a lot of time examining the condenser for leaks but nothing missing jumped out at me. I'll look again over the course of the next week. I'll be taking things apart to look in between the condenser and the radiator. I'd love to find a "smoking gun" there!

Dougflas wrote:That machine you posted does not reclaim. It is only for recovery. You would have to use new refrigerant if you used that machine. And as mentioned, it does not separate refrigerant from oil.

Yes, only a recovery machine. I've also looked at the Mastercool 69000 which does separate the oil. More money but it is assembled in the USA. Undoubtedly full of china parts like everything else. I spoke on the phone with Mastercool last week and they did confirm that I won't be able to reuse the refrigerant recovered with the 69000 because it isn't a reclaiming machine.

I'm planning on using virgin R134a.

Do your fans have a wattage number stamped on them somewhere or maybe online somewhere? If yes, we can derive the amps. Maybe, let's say = 240 watts? 20 amps x 12 volts = 240 watts.

A clamp on ammeter can also measure amperage though maybe less accurately.

Rick