PeachParts Mercedes-Benz Forum - View Single Post - Poor AC Cooling at Low Engine Speed...Why?

JamesDean · #4 07-15-2012, 03:52 PM

Well here's the cars:

1993 190E M103, 10P15C, charged with ES-12A Hydrocarbon

I charged it up when it was about 85F outside. At high idle with fans on.
I achieved about 25 psi low side, 165 psi high side.

At low idle, cooling is rubbish, 50-60s vent temp.
At >1500, cooling is excellent. Mid 30's vent temps.

The system probably could use some work done to it. I know it has a leak somewhere as my original R12 charge from 2006 leaked out in under a year. The ES-12A stuff lasts quite a bit longer. I topped off the car after 2 years since previous charge.

Would there be any advantage to replacing the 10P15C with the 10P17C? I know the 17 is higher displacement unit...

1982 300SD 617, R4, charged with Freeze12 then ES-12A Hydrocarbon

We got this car in 2007, the R4 failed, we had the shop replace it, and the dryer. I dont think they replaced the TXV as it was still in working order. They charged it with Freeze12 as R12 was considerably more expensive. The F12 stuff worked OK but a while then progressively got crappier.

So it was vented one day, accidentally, and I figured I'd try charging it up with the ES-12A stuff I had left over from the 190E.

I dont remember the pressures but it was able to achieve low 50/high 40 at speed, but like my 190E was crappy at idle.

1989 420SEL 116, 10P17C, charged with R12

Like the SD, the compressor on this car died and I had the shop replace it and charge it with R12. The performance was lackluster, and degraded over time. I had some R12 stock built up for when my other SD needed it, so I decided to try to recharge the 420...

It took a few tries but I think I got it right finally. It has a 5-7 degree difference between idle and at speed vent temps but I think its still pretty good. I was able to keep the car cool when it his 100F not too many days ago.

I know from the three cars I mentioned here that it looks like the refrigerant is the common component but I know other people use the ES-12A stuff with good results.

I tend to think that the 190E's system could use an overhaul, especially seals and valves. Maybe even the compressor, at 85F the best I could get out of the compressor (without making the low side too high) was about 165 Psi.

I think the 300SD needs to be evacuated and recharged with the ES-12 Industrial stuff (as the ES-12A is not meant to be charged into a vacuum) I think there is some remnant F12 in there causing problems. Probably should replace the dryer too. But I lack the tools for such endeavors. I just have a manifold set, no vacuuming abilities.