You use a dipstick to measure the oil attached file has plans for one you can use a wire coat hanger to make one. You can also buy them at AC supply stores. As for oil to use you need to use oil that is compatible with your refrigerent. When you converted to R134 you should have changed oil to ester oil. R12 uses mineral oil, it will not mix with the R-134a refrigerant. That is why you need to change it to Ester oil, because it will mix with R-134and lubricate the system components. Suck out the mineral oil and add ester oil you got R134 and PAG oil in the hoses then use PAG oil Viscosity 46in compressor.
Here's what happened: Looks like my compressor was bad, when we put oil in and charged it up, it was slipping the clutch and wouldn't turn by hand. So, I went to the trusty U-Pull it. And guess what? there was a butt ugly orange 80's mustang 5.0 that had a very similar compressor. It was $13. It had been painted black recently which led me to believe it had been rebuilt at some point. It had a different clutch so I took the clutch off of my dead york compressor and put it on the motorcraft. Then, after looking all around town, I found that Pep Boys sells an ester oil by castrol that is synthetic, and compatible with both R-12 and 134a lubricants. I filled the motorcraft compressor with 8oz of that, then it bolted right up to the mercedes bracket, while at the same time installing the new dryer from NAPA (it was only $18 there by the way)
I sucked all the air out of the system with a vacuum pump, filled it, and oh no!!! it didn't work! it was kicking on and off over and over. After hours of poking around here and there, I noticed that the motorcraft compressor has the suction side on the left!!! The Ford compressors have the suction and discharge sides backwards!!!
So, I emptied it again, switched the hoses, ran the vacuum pump once more, and filled it with some PAG and almost 3 cans of 134a. And it started working!!! yay!!!
Now, there's AC in my Merc, just in time for the heat wave here in PA. Thanks a lot everyone, it was my first AC repair project and I have learned a lot here.
Last edited by egny280CE : 06-06-2008 at 01:25 PM.
Reason: grammar
Yes tomorrow supose to be HOT on the east coast. $13 for compressor Great deal. Glad you got it running. DO you have and instant read thermometer to measure your vent temperature? Let me know on my post what it is.
I just converted my 1981 Mercedes 300SD from the old R-12 to the newer R134a system. The garage did the work. I provided all the parts including a new R4 compressor from four Seasons, PAG 150 with dye, dryer, both switches, and expansion valve. I had to leave for a time and when I got back they were pulling it into a vacum for 30 minutes which held and then charged the unit with R134a at about 95% of orginal charge. They said they were unable to replace the expansion valve because it needed a special tool also that the unit was so clean that it did not need to be replaced. Low side presser is about 35lbs high about 125 at 2000RPM. Problem is that I am only getting 54 degrees out of the vents whereas the R-12 was putting out 45 degrees. Outside temp was at 77 degrees and that only gives me 23 degrees difference and it should be at least 30 degrees between the two. Any ideas on how to correct this or is this what to except with a R134a system. NOTE: Just got back from a 100 mile run outsidr temp was 82.2 degrees, vent temp was 57.2 degrees. Also the 2oz. of BG oil was added after the unit was fully charged. UPDATE: I removed 6 ozs. of R134a and the oil that came out with it then took the car down to Arkansas, a 250 mile trip and got the vent temp down to 45 degrees. This was more than the 30 degrees I expected as the outside temp was in the 80s. Advice: don't overcharge with 134a, and forget about the sight glass it is for R-12.
Last edited by william gunkel : 06-21-2008 at 07:16 AM.
Reason: Updated Infromation.
Linear Mode
