Automotive Air Conditioning Information Forum

GM recommends PAG 46 for almost all their systems except those with R4 compressors. If the compressor is an R4, use PAG 150 in it. And don't look at it sideways. They aren't reliable to begin with.

Every listing I see for a 1987 truck is the R4 compressor.

Without knowing what the previous owner(s) may have done, you have blown up two compressors. You have high head pressures.

High pressures and poor cooling are usually due to hot refrigerant.

The primary filter in that system is a condenser with multiple paths. You have even noted a restriction in the condenser.

The replacement condenser listed for 1987 trucks is a 6mm Piccolo type. The OEM unit may have been a Serpentine. Both types can have blockages that will reduce the condenser capacity to less than 50% of original, but seem to be ok when blowing air through them. Neither design can be flushed effectively without special equipment, and even then sometimes they are scrap.

Buy a new condenser.

.

bohica2xo wrote:Every listing I see for a 1987 truck is the R4 compressor.

Without knowing what the previous owner(s) may have done, you have blown up two compressors. You have high head pressures.

High pressures and poor cooling are usually due to hot refrigerant.

The primary filter in that system is a condenser with multiple paths. You have even noted a restriction in the condenser.

The replacement condenser listed for 1987 trucks is a 6mm Piccolo type. The OEM unit may have been a Serpentine. Both types can have blockages that will reduce the condenser capacity to less than 50% of original, but seem to be ok when blowing air through them. Neither design can be flushed effectively without special equipment, and even then sometimes they are scrap.

Buy a new condenser.

.

Factory compressor with big block is the H6.

New condenser is sitting in the garage - factory replacement parallel flow style. Seems I might also have a low voltage problem at the compressor clutch, but I will start a separate thread on that.

Cant anything be easy? The GM factory replacement condenser is about 2" smaller than the original and doesn't fit into the mounts. Ugh. No part number on the condenser so I am wondering if it is the correct part? Supposed to be a parallel flow that replaces the original. It is smaller overall and thinner.

jeepsj wrote:Cant anything be easy? The GM factory replacement condenser is about 2" smaller than the original and doesn't fit into the mounts.

Sounds like issues I've encountered with GM parts. Like water pump for 2005 6.0 Yukon XL being different than the one for 2005 6.0 Yukon XL Denali (different part numbers)

Mmmm...looks good.



This is the oil that came out of the hose.



That was less than an hour of operation.

Wow, That looks pretty bad...

I have a 76 Chevy full size truck I want to refit the a/c on and appreciate what you are trying to do. My current issues with a factory r-134a system have me doubting my skills.

Keep at it, you'll get it right!

Doug

Lesson learned - just contact Tim and get all of your parts through him. Going through other suppliers for some of the parts netted me some crap parts that are being sent back and I'm having ACKits expedite new parts to me.

Any thoughts on how converting to this condenser -

http://www.ackits.com/index.php?route=p ... CN+3642PFC

Is going to affect overall system capacity? I think this throws the whole "80% rule" out the window on the 134a capacity. So charge by pressures and vent temps?

Well I finally got the time to finish everything up and get it charged this weekend. Factory R12 charge is 52 ounces. It vacuumed down nicely and all was good. I pushed in the first can as liquid with the system off and into the high side port. Started charging it up and interior temps were steadily dropping. Ambient temp was about 102. I was putting in the 3rd can and pressures were 45-ish on the low, and 230-ish on the high and the vent temps were down to 51. It stopped dropping and stayed at 51 for a while as I kept adding R134. Then the temp jumped to 53. At that point I figured it was full.

An 80% charge would have been about 41 ounces. In another thread, Tim said that with swapping from a serpentine to a true PFC, the charge could be as high as the R12 charge. I figure I got in about 33 ounces before I stopped.

While I'm driving the vent temps are great hovering right at or just under 50 . Idling at a light, They go up to 55-57.

Should I have kept adding? Am I good where I am?