a/c question

[Arizona_928]

I switched my a/c on the turbo from R-12 to 134a. I put the new oil in air compressor. Pressurized the system for leaks, no leaks at any of the connectors in the engine bay. I vacuumed the system for around a hour to a hour and 15 mins. The gauges read -15psi low side the whole time. I put in a can of 134a the highside jumped really high to 350psi, low side i think was 60. but the low side would go down when rev to 2000 RPM. But only was able to get one 12 oz can in. I didn't feel safe putting anymore in. The a/c blows coldish on the freeways, at idle not so much. Also when on the freeways the car was running hotter then usual; exactly at the second white line. usually she runs middle to the bottom white line. Radiator fans engage how they are supposed to.

What do you guys think? I'm not used to a/c. I usually just enjoy driving with the windows down and the sunroof in the hatch!

[968 GUY]

did you put the freon in the low press. side?(fitting is next to compressor, I lifted the car and went in behind wheel). If you did, the expansion valve could be bad.

[Arizona_928]

nope, I put the freon at the connectors up top by the driverside top strut mount. I'm still using the R12 fittings.

[alfadoc]

Originally Posted by 968 GUY

did you put the freon in the low press. side?(fitting is next to compressor

Inaccurate information. On 85.5 and 86, low side is next to driver's strut tower, high side is by the receiver dryer. 87-up, low side is on the compressor, high side is by the shock tower.

[Arizona_928]

hold on guys this for a 1986 951. let me take a picture.

[Arizona_928]

Is this the high and low side?

[looneybin]

yep, the larger diameter pipe is the low side

[Arizona_928]

Originally Posted by looneybin

yep, the larger diameter pipe is the low side

Awesome! I hooked up my gauges right then.

[John_AZ]

Originally Posted by AZ_porschekid

I switched my a/c on the turbo from R-12 to 134a.

I put the new oil in air compressor.

Just a guess, was it a can of R134a oil charge?

Pressurized the system for leaks, no leaks at any of the connectors in the engine bay.

The usual method to pressurize is to add 1/2 can of R134a and search for leaks.

I vacuumed the system for around a hour to a hour and 15 mins.
The gauges read -15psi low side the whole time.

Do you have a 2.5cfm vacuum pump or the small venturi pump that uses a home compressor?

I put in a can of 134a the highside jumped really high to 350psi, low side i think was 60. but the low side would go down when rev to 2000 RPM. But only was able to get one 12 oz can in.

With the guages correctly connected as you mentioned to the high (skinny line) and low (fat line) , are you sure you opened the low side valve on the AC guage and installed the R134a into the low side line?

The low side is too high.

The normal guage readings at 80 degree outside temp in front of the condensor
(ambient) should be 190-220 psi high side and 30-40 psi low side. IF it was 110F outside when you installed the R134a then the high side could be 250-300psi and the low side 50-60psi

I didn't feel safe putting anymore in. The a/c blows coldish on the freeways, at idle not so much.

Grab the hoses going into and out of the dash at the firewall. One hose should be hot and one cold (er/warm)

Also when on the freeways the car was running hotter then usual; exactly at the second white line. usually she runs middle to the bottom white line. Radiator fans engage how they are supposed to.

What do you guys think? I'm not used to a/c.

I usually just enjoy driving with the windows down and the sunroof in the hatch!

Yeah, I really enjoyed the 26 days of over 110F!

From the top^

Freon is installed at about 1200 to 1500rpm.

Plus, if you have to open the lines on the AC again, replace the 2 schroeder valves on the high/low ports. The old valves may leak due to age.

Here is the page From Clarks on AC and the problems you have.

Air Conditioning Troubleshooting and Repair

GL
John

[AaronM]

Unless you're taking these measurements with an ambient temperature of 120 degrees (Fahrenheit, which, I admit, is a possibility in PHX), your system is seems over-charged.

Take a look at the pressure chart on Clarks' Garage (bottom of the page) for an example of what you should be seeing at a given ambient temperature.

Car is definitely going to run a little hotter with the A/C on when the weather is hot. The condenser sits in front of the radiator and when the A/C is on, the condenser gets hot so the radiator has warmer air passing over it and the water temp edges up.

When you switched over, did you also change out the receiver/drier? That's necessary on a switch from R-12 to R-134a because no matter what you do the desiccant in the receiver/drier will hold onto the old oil and you'll risk issues with the incompatible oils mixing. Regardless, R-134a is not as effective as R-12, so even if everything is done perfectly, you can expect to lose a little bit of cooling due to the switchover.

[Arizona_928]

It was around 100 when I did the a/c, but was really humid out.
I dropped the compressor, but there wasn't any oil in there so I added 2 oz of the peg oil I think? But it's the stuff compatible with the 134a. I replaced a the o rings at the compressor then pressurized the system with compressed air. The vacuum pump was the 2.5cfm harbor freight one. I noticed that the low side was really high too, but when you gave it a little gas (1200 RPM) it would drop to 40psi, but the high side was not moving. Ok I'll try not to burn myself with those last two!

BTW it wasn't that bad.....

I didn't replace the drier or receiver. Awesome! I just don't want to over heat the car running the A/C

[John_AZ]

What is the PAG weight?
PAG-46 is the correct weight.

If you used PAG 100 or higher it might have damaged the compressor.

John

[Arizona_928]

I think i might drain the system and try everything again. i did add dye to check for leaks. it's going to be messy!

It was the PAG 46. Do you think the low side having the high pressure would be the compressor going out?

[John_AZ]

A good idea.

Did you add the PAG 46 to the suction port of the compressor?

Replace the receiver/dryer like AaronM sugested. Universal are cheap on Pelican or go local.
The receiver/dryer may be clogged.

Replace the Schrader Valves on the test ports.

Vacuum for an hour or more to remove any air and moisture in the system. Turn off & check back after 1 hour to see if it held the vacuum.

To avoid overheating the engine, spray Simple Green on the condensor fins and let soak.
Flush from the engine side!

I use a low temp radiator fan relay combined with a low temp thermostat. One step below OEM on both. While this is not the best idea in a normal climate because the engine and emissions require a higher temperature, I found in PHX it works due to the high temps.

Compressor "going out" ? No. Many things could cause the high pressures. One of the most common failure parts is the expansion valve like 968 GUY mentioned. If it sticks in the "open" position it would give a higher low & high pressure reading.

GL
John