I've been unable to find what normal hi and lo pressures should be on my SDL. I suspect its overcharged and when I take it to the shop I suspect they won't know either.

Anybody have a source?

Thanks

Harry

www.ackits.com

Will depend on ambient temp at condenser and type of
refrigerant. ACKits shows both R-12 and R-134a tables.

I did my A/C in the W123 this weekend. Pressures were 240
high, and 40 low at 94F using R-12 after a 2.6lb charge by
weight.

pretty much right on the money per the chart.

Thanks Techguy, I had also asked the question at the ACKits forum and Tim said his data did not cover it. He said he would not like to see anything over 325.

Harry

You sure you want to go to that shop???

__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

Hi Hit Man

HA HA, I know what you mean but they do have a gauge set and I don't. I have eight inches of books for this car including the ACC Service manual and I have this question posted on three sites. The ACC manual is for 126 but it only has a suppliment for MY 86, 87 and 88. Its not there and so for no one has posted it on the three sites.

Thanks
Harry, waiting and watching

I'm going through my SDLs system now, I don't want to kill a $400 compressor. Just ordered exp valve, dryer, switches on dryer, and more.

__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

Didn't cover what? Do you have something other than R-12 or R-134a in the system?

I thought 240psi was slightly on the high side. I can only wonder
what 320+ would do to the compressor long term.

Looks like I'll let yall know. This stupid AC stuff and non-performing Freeze12 has shot my wheels off. AND keeps me sweating.
95-100 degrees, 32-37 low, around 300 high. 60 degrees at idle, and might get down to 56 driving. Not good enough.....
Pressures were at hi idle, around 1500 rpm (if I had a working tach!)
This is a "Hate this stupid car" phase.

__________________
Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John

techguy

It was converted to 134 four years ago by the PO and I've owned it over two years with good AC until this month. What Tim could not find is data on the 86 300SDL. That's my problem, I believe I have most if not all of the printed manuals but the car came along late and the 86, 87 and 88 model years were only covered by a suppliment in the back of the ACC FSM.

I would like to know what the pressures should be so when the gauges are used I can say, wow, that's much too high, or whew that's just right, or boy, we need more stuff.

Thanks

Harry still waiting.

JimmyL

Thanks for the information on SDL AC pressures. Are these readings from your car or did they come from some other source? I think techguy has it right or pretty close at 240, 300 on the high side seems excessive.

If these are readings from your car maybe you also need to find out what's correct because you don't seem to be happy with the cooling results.

I'll post when/if I get a valid source.

BTW, I have a Texas friendly white 240D manual that's in pretty good shape. However the AC quit on it yesterday.

Thanks
Harry

Air flow has to be right before you can really adjust the pressure. If the evaporator has clogged up on the fins as it will since they have no cabin filter, then you will have minimal heat transfer. If you have a clogged evap and a dirty condensor then they can cancel each other out and you can get normal pressures on the gage, but less than optimally cool air.

A/C is a delicate balance of air flow and refrigerant pressure when depend on each other.

__________________
1981 300D 147k
1998 VW Jetta Tdi 320k
2001 Dodge Ram 2500 141k
1979 300D 234k (sold)
1984 300D "Astor" 262k(sold)
Mercedes How-To and Repair Pictorials
I love the smell of diesel smoke in my hair

Diesel Giant

I have really enjoyed your DIY site, thanks for sharing your knowledge and helping us shade tree wanna-bees. I could never put it together like you have but I can imagine its not quick nor easy. Too many details for me. Doing a job is one thing, but doing it and recording it for others has got to be a mighty task. I'll bet you have to clean your hands a lot in order to take the shots.

Thanks for your input on my problem. The cooling was excellent until this month. It appears the KLIMA is bad and I have a new one on the way. I went through 6 or 7 tests in the ACC FSM to make that determination. I'll know about that tomorrow.

What I don't know is what my hi and lo pressures should be. Any sources for that information at your place?

Harry

Did you test out the CCU and such? See the thread from me on it.

__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

Harry, just to clarify, I was just posting what my pressures are, not necessarily what yours should be. I think you know that, but just wanted to be sure.
I did find out it was over a 100 here today, but my F-150 has 41 degree vent temps no matter what. This MB is just poor. I was doing better with R134A, with the same evap situation, but I may remove the blower fan tomorrow and see if I can see anything up in the evap zone......



Heck Harry, sounds like it is definitely time to get rid of the 240!!! Texas friendly white, huh?

__________________
Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John

bohica from the autoacforum answered my question from a Mercedes TSB, its hard to beat that source.

der Dieseling Doktor mbooth replied on the Kaleb Diesel List that the dryer fan switch is pressure, not temp.

Boy, are these high pressures or not?


bohica2xo
Senior Member

Posts: 1651
Joined: Apr 2002
Fri July 14, 2006 4:15 AM (NEW!)



Harrywat:

Here are some specs for your W126.125 benz:

The Temperature Switch on the dryer starts the aux fan at 55c. It should open again by 12c . You can test the fan operation by disconnecting the switch, and jumpering the connector. The temp switch is located on the top of the dryer, with the discharge line. The switch on the side of the dryer is the pressure switch. The pressure switch should be closed on a properly charged system.

Mercedes uses a chart of paramters for performance testing that model. This takes into account both ambient temperature, and humidity. All tests are done at 2000 engine rpm, doors closed, windows open, cabin fan on highest speed. You must run in this condition for Ten Minutes before recording data. The specs for 92f ambient are:

At 40% RH, the center vent should be 50f to 52f, the high side 312 to 325 psi, the low side 29 psi.

At 90% RH, the center vent should be 63f to 66f, the high side 342 to 370 psi, the low side 36 to 39 psi



Tha absolute worst case on the chart is 104f ambient, at 90% humidity. Center vent temp 70f to 73f, the high side 380 to 394 psi, the low side 45 to 51 psi.

According to mercedes TSB's if a proper retrofit was done to the manufacturers specifications, the R134a performance will be the same as the R12 performance. They stress repeatedly the necessity of removing all of the old mineral oil, and replacing the dryer with the proper unit.

.