1990 300E (124) A/C Help
 

Hi All,

I recently bought a 90 300E and wanted to convert from R12 to 134a freon. I've done it on my 86 300E and love it.

I took it to the shop that did the conversion on my older 300E, they flushed the system and fixed a connection leak between the a/c line and the compressor. After changing the compressor oil they filled the system with the new 134a freon. Compressor started right up and the vents began blowing cold air, but after 2-3 minutes the compressor shut off and wont turn on again. The shop says everything was well, compressor sounded normal the air was blowing cold, then suddenly the compressor shut off. The shop believes its an electrical issue and wants a electrical technician to trouble shoot the problem.

The shop said the pressure on both low/high sides were within normal range.

Can anyone help? is there a fuse? Any suggestions?

Thanks
GP

Are you saying that you did a conversion on an a/c system that was working okay?

I am not a proponent of converting 12 systems to 134a in general, but especially not a 124 car. It just doesn't have enough condensor capacity to be a good candidate. With the price R12 coming down and the price of R134a going up I just don't see the need of the conversion anyway.

All that said, you need to start your troubleshooting procedure at the clutch connection with a voltmeter to see if it is getting actuation voltage. If it is, ohm the clutch to see that the coil still has continuity.

If there is no voltage at the clutch connector, trace the circuit backwards through the r/d pressure switch. While testing all this, keep in mind that the climate control does not pull in the compressor for a few seconds after starting the engine to make sure that there is engine oil pressure before loading the engine with the compressor load.

does your car have the mas relay over by the battery or a n a/c relay about the same size as the fuel pump relay?

Since the summers in Michigan arent that long, 134a works fine here. I converted my 300D last summer. Since I knew the compressor was in working order and the system kept its charge, all I did was get the conversion kit (got mine from napa) from just about any parts store. Just follow the instructions.

It would be good to have a decent set of ac gages instead of the one that comes with the kit but it'll work fine.

Mine works great:D .

I decided against continuing with r12 cuz they seem to be difficult to get a hold of while walmart carries 134 :)

I also have a 1990 300E that needs the conversion kit. Can you tell me what parts come in the kit. Your post does not mention any new parts as part of the kit. I live in New York City and was quoted a price of about $400.00 parts and labor. Mercedes dealers would charge about $700.00. Can you reccommend a major auto chain that can do a compentent job?
I found your post by doing a Google search.

Thank you,

kwelleri

You can buy a kit as cheap as 20 bucks that has the refrigerant and oil as well as the adaptors. I wouldnt use it though. If I was gonna convert, which I would not, I would have a reputable shop do it the right way and just pay the good money to do so. It would be worth the extra cash.

I would suggest evacuating the old refrigerant first b4 converting by pulling vacuum then charging while it is in a vacuum.

I used a vacuum pump.