Hi guys, I just bought a w201 a few weeks ago. I had the A/C recovered and I pulled vacuum on it today for a little over an hour, and it held vacuum for 30 minutes no problem.

I filled with r12 (two 18oz cans, pretty close to 2.2lbs, I'm tired and the math eludes me). It was about 88* and I was at ~35psi Low and 250ish High but the aux fans weren't on. I was only getting about 15* reduction from ambient temp at the center vents, 20* max at 55mph.

What am I missing? Even without the aux fans, it should be more efficient at idle. Also, the high side seem high, but again I'm not sure if that's due to the aux fans not working. It doesn't seem high enough for TXV issues, but I'm not an expert.

Any ideas?

Thanks guys!

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1997 E300 Diesel - 222K miles

BUT,Even I know,"Pressure Test" is the definitive Test for A/C systems.
[ Pressurized NITROGEN with a Touch of R-12 for diagnosis.]

When you "Added" the Refrigerant did you make absolutely sure NO Ambient Air
could be introduced into the system? [Ambient Air has a lot more moisture in it
than you think.]

Was the System EVER "Broached" without replacing the Receiver/Dryer?
What's the Lubricant level like?
How Clean are the fins on the Condenser,Radiator and Evaporator?

It's working,just not as well as it should.

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'84 300SD sold
124.128

It had pressure before it was recovered and I pulled vacuum, just not much. The condensor looks ok. I know I didn't introduce an atmosphere, but I didn't replace the reciever drier.

I dont know how the evaporator looks, but I think its accessible from the outside, under the cowl?

Also, I'd like to get the auxiliary fans going and see what that does.

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1997 E300 Diesel - 222K miles

I always replace the receiver/drier if I open the system.

Also, without the aux. fans running, the high side will get too high and the pressure switch on the drier will do its job and shut off the compressor.

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1993 190E 2.3
2001 SLK230
1971 LS5 (454) Corvette Convertible

Here's a link to some pressures you should be seeing:
http://www.ackits.com/aacf/ptchart.cfm

At 90F, you should be seeing 190-230 on the high side, which you seem to be getting. The low side, they say, is about 22 psi.

When you noted your numbers was this at idle or at higher rpm like 1500 rpms?

When I charged up my 420SEL (R12) I tripped the auxiliary fan, and disconnected the idle control system so that the car idled at 1500 rpms, then met the numbers in the chart appropriate for my ambient temp. You might want to try that..

W201's center vents are directly attached to the evaporator you should be getting rather low numbers from them compared to a w126. My 190E, last time I checked, gave me high 30's when it was high 70, low 80s outside. I don't have R12, but rather ES-12A.

__________________
Cruise Control not working? Send me PM or email (jamesdean59@gmail.com). I might be able to help out.
Check here for compatibility, diagnostics, and availability!

(4/11/2020: Hi Everyone! I am still taking orders and replying to emails/PMs/etc, I appreciate your patience in these crazy times. Stay safe and healthy!)


82 300SD 145k
89 420SEL 210k
89 560SEL 118k
90 300SE 262k RIP 5/25/2010
90 560SEL 154k
91 300D 2.5 Turbo. 241k
93 190E 3.0 235k
93 300E 195k

Thanks for the input!

The numbers were at actual idle, and my idle was stumbling a bit. I just replaced the spark plugs with the correct NGK ones and it idles smoothly now.

Should my reading by taken at ~1500rpm? If so then I'm probably undercharged.

With domestics, I'll usually raise the rpm on small cars but I wasn't sure if I should on the w201. Domestics tend to be more forgiving with their large accumulators taking up a lot of slop.

Thanks again.

(P.S. Who decided to put the high side port where it is? Geeze?)

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1997 E300 Diesel - 222K miles

the pressures you are reporting make me think bad fan clutch, and contaminated system.
vacuum holding for 30 minutes how? do you have a micron gauge to see pressure change?
the rubber hoses, and leaky compressor in mobile a/c systems are NOT designed to have extended vacuum done on them. nitrogen flush, and quick high cfm vacuum, is needed in automotive applications.

the 30psi low is fine, but the 250 high is out of range... at idle. most likely, you have air in the system from the vacuum, and changing cans during the charge.
if it were me, I'd dump it all, and change the dryer, and purge everything with Nitro, then leak test under pressure with a splash of R22, then evacuate that and charge from a 30LB cylinder of 12... but I've got all that stuff.

put a jumper on the pressure switch leads, so the aux fans stick on, and bump the idle up to 1500 or so, and tell us what you have.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!