The 87 300d is finally getting the A/C RandR it deserves.
Anyways, I have some gauges and I'm charging the Freon level. I had the compressor off and replaced it and the dryer. I also ordered a new expansion valve but when I saw where it was (Behind the brake booster) it scared me. I pulled a 29"HG vac and it held just fine. Anyways, I started charging it. Here are my numbers:

Car not running:
Low Side-Pegged
High Side-160psi or so

Car Running at idle:
Low Side-110psi
High Side-Pegged until the compressor shuts off. I jumpered the low pressure/level switch on the dryer a moment and the compressor stays on. With out it jumpered it cuts on and off ever 10 seconds or so.


Lastly when the car turns off Low and High should equalize. Am I right??

Any ideas what's the matter here? My guess is maybe the expansion valve.

__________________
-E300d '99 350k
-Suburban '93 220k
-TDI Jetta '03 350k
Sold
-F250 '96 7.3
-Dodge Ram 12V
-E320 '95 200k
-E320 Wagon 1994 155k
-300d Turbo '87 187k miles
-E320 1994 200k
-300d Turbo '84 245k (sold to Dan62)
-300d Turbo '84 180k
-300sd '80 300k
-7.3 Powerstroke Diesel 15P Van 500k+ miles
-190d '89 Non Turbo 2.5 5cyl 240k (my first MB)
Tom's Imports of Columbia MO Ruined the IP in changing leaky delivery valve O-Rings - Refused to stand behind his work. Mid-MO MB drivers-AVOID Tom's.

I do my low pressure reading the the compressor on and running the engine at 1500 rpms. Should be in the mid 30 range with this heat.

if it is higher, you need freon.

Expansion valve is a pain in the neck.... or right hand... there are some hoses that you can move out of the way a bit... but I scraped up my hand a bit..

then i forgot an o-ring and had to do it again.... most will recommend puttign blue nylog on the o-rings. some will say not necessary. i bought the stuff and used it. at worst, it helped keep the o-rings in place.

i took mine to a professional to pull vaccuum... don't have the tools..also then they could tell me for sure if there was a leak.

that's my story... this was on an 89 124.. a 300CE

__________________
1989 300ce 129k
( facelifted front,updated tail lights, lowered suspension,bilstein sports, lorinser front spoiler, MOMO steering wheel, remus exhaust,stainless steel brake lines). (Gone)

1997 s320 154k (what a ride). Sold with 179k miles. Replaced with Hyundai Equus

1994 e320 Cabriolet 108k



1972 280se 4.5 153k Owned for 12 yrs, sorry I sold it


[/SIGPIC]

Is there a way to tell if the expansion valve is good still? I really don't want to change it and there are no leaks based on my vacuum.

__________________
-E300d '99 350k
-Suburban '93 220k
-TDI Jetta '03 350k
Sold
-F250 '96 7.3
-Dodge Ram 12V
-E320 '95 200k
-E320 Wagon 1994 155k
-300d Turbo '87 187k miles
-E320 1994 200k
-300d Turbo '84 245k (sold to Dan62)
-300d Turbo '84 180k
-300sd '80 300k
-7.3 Powerstroke Diesel 15P Van 500k+ miles
-190d '89 Non Turbo 2.5 5cyl 240k (my first MB)
Tom's Imports of Columbia MO Ruined the IP in changing leaky delivery valve O-Rings - Refused to stand behind his work. Mid-MO MB drivers-AVOID Tom's.

HIGH SIDE GUAGE PEGGED WHEN RUNNING?!!!! that's over 500psi! you are overcharged. WAY too much freon in the system. or you have a VERY small condenser.

__________________
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 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Sounds way way way way way way overcharged. It might also have too much refrigerant in there. The 10 second cycling is the overpressure protection cutting out the compressor. Evacuate it and start over.

You do know not to open the high side valve on the gauges while the system is running?

- JimY

The low being pegged when not running has me wondering...as when the system is not running, both sides should be equal.

When you are either running the compressor or letting it kick in or out, does the air get cold at the vents?

Did you check to make sure no rubber lines are kinked?

How much freon did you install? 3 12oz cans should be tops, and depending on what freon you are using, it could be over charged with three cans.

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RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

99 W210 E300 Turbo Diesel, chipped, DPF/Converter Delete. Still needs EGR Delete, 232K

90 Dodge D250 5.9 Cummins/5 speed. 400K

Gone and still missed...1982 w123 300D, 1991 w124 300D

So it could be overcharged or it could have too much refrigerant?

If I'm gonna make a guess..... it's overcharged with too much refrigerant.

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'85 300D Turbo - CA Version

We don't know that it's not equal. Keep in mind that the high-side and low-side gauges don't use the same scale. 160 psi is off the scale for many low-side gauges. High side gauges typically peg around 500 psi, low side around 120 psi.

Is your auxillary fan working? This could explain your high side pressures. The high pressures you are reading are extremely dangerous. I'm surprised none of your hoses exploded. Make sure you know what you are doing.

Scott

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Scott
1982 Mercedes 240D, 4 speed, 275,000
1988 Porsche 944 Turbo S (70,000)
1987 Porsche 911 Coupe 109,000 (sold)
1998 Mercedes E300 TurboDiesel 147,000 (sold)
1985 Mercedes 300D 227,000 (totaled by inattentive driver with no insurance!)
1997 Mercedes E300 Diesel 236,000 (sold)
1995 Ducati 900SS (sold)
1987 VW Jetta GLI 157,000 (sold)
1986 Camaro 125,000 (sold - P.O.S.)
1977 Corvette L82 125,000 (sold)
1965 Pontiac GTO 15,000 restored (sold)

thats scary... good old mercedes parts though, took all the torture.

__________________
Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac?

As long as they would add one additional commandment for you to keep thy religion to thyself.
George Carlin (Wonder where he is now..)

1981 240d (engine donor 1983 240d) recently rebuilt engine hurray! - No more.. fought a tree and the tree won.

pearl black 1983 240d 4speed (Converted!@$$%) atleast the tranny was rebuilt.

The other issue is that the original poster doesn't mention whether he flushed the system. If the compressor crapped out and blocked up the expansion valve that could be part of the problem here. Still, I agree the first step is to pull out the refrigerant. I'm guessing we're talking about R134a here?

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Tjohn

82 300 SD
77 450 SL (gone)

With low side pressure off the charts?

Naw, you're right. I when I read the guage was pegged, I still mentally was thinking he meant at the bottom.

__________________
Tjohn

82 300 SD
77 450 SL (gone)

You might be right; it could be "pegged" on either end of the spectrum.