Hi,
I have a1982, 200TD Turbo,

today I installed a new the heater monovalve recoonditinion unit I ordered from Merc Shop.
I am sure it is cutting off the heat when I short the ground side pin to the chassie.

I need to make this ground line myself as I seem to have destroyed the ground path through the automatic climate control unit.

I have read the several informative post on heater control problems/solutions but I still have some questions as the circuit diagram in the Haynes manual doesn't explicitally help me.

My questions are:
1. What ciruit do I need to replace/repair/recondtioning to restore the ground side of the heater control valve? The push button controls still work as I can turn the AC on/off and can regulate the fan speed etc, but only get hot hot air if I don't close the ciruit by shorting the ground side. Also the temperature set control still works as the fan speed increases/decreases as I turn the temperaure control away the present inside temperature.

2. When I do manually shut off the heater vavle and turn on the AC, the air does not seem that cool. I have just had the AC recharged. They put in 2.2lbs of Freon, I think the pressaure was about 2.9. Is this enough freon or is the AC compressor not working well? I read about oil in the compressor. Where is the oil put in?

3. I need to change the lower oil line to the oil cooler. The shop quoated me 4 hours labor, but to me it looks like 1/2 hour job, once the oil is drained. I am thinking of ordering the oil line and changing it myself. Is this advisable?

4. To help with the blow by, I plna to use 15w 50. Is this oil grade OK in warm temperatures?

thanks, this is a great forum I have learnt so much by by readingup on the old posts.

Michael

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New 300TB Turbodiesal Owner
Home Mechanic

#1 - The pushbutton controller in that year was just a switch board. The electronic were in two separate controllers behind the glove box. They are somewhere in size between a paper back novel and a pack of cigarettes. The Temp Controller is in a silver metal can and the Blower controller is a black plastic box. The circuit to the mono valve passes through the switches of the pushbutton controller into the Temp controller except in Min and Max positions which are delt with in the PBC.

#2 - Your impression of pressures are wrong. Proper pressures on the "Cold" side (low pressure) should drop to around the high 20's psi. The high side will be above 200psi and be dependent on many things including the ambient air temp.

The oil in the compressor/system is best left to professionals. It really shouldn't be delt with except with major repairs. You can not add oil to a pressurized system without special tools and training.

#3 - We usually get two hours to replace both lines (the only way we do it). You have eyes bigger than your fingers if you think its a half hour job. I doubt you will like the job.

#4 - We use 20w50 oil all year round here in Florida.

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

#1 - I will take a look. Thanks

#2 - I was referring to the filling pressure and not the running pressure. But I guess the running pressures is the relavent ones if I want cold air.

#3 - "We usually get two hours to replace both lines (the only way we do it). You have eyes bigger than your fingers if you think its a half hour job. I doubt you will like the job. "

Great reply, made me laugh, but 2 hours for two nuts and two bolts. I guess I am going to get good and oil splatterred. I think I also need to change the oil filter cannister/engine block gasket as it looks like I have a oil leak there. Sometimes it leaks a lot other times it drips just a little. Any clues on why this would be?

#4 - In this part of Northern CA, the temperature is mostly in the 85s. I once knew, but what does 20W50 mean and should the numbers increase or decrease for hotter or colder climates?

thanks Michael

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82 300TD Turbodiesal +250, 000
86 Volvo 740 GLE 220000
85 Honda Civic 120000

#2 - The only pressures that matter are working pressures. The pressure of the system at rest is only a factor of the ambient temperature once there is liquid in the system.

#3 - The gasket between the oil filter housing and the block has been redesigned. It currently it a mixture of metal and gasket material and weights about three times what the original gasket did. The new # is 616 184 07 80.

#4 - When refering to oil viscosity, numbers like 20w50 are refered to as multi-viscosity oils. This is actually misleading as the benefit to these oils are that they are viscosity stabilized. This means that they stay at the same viscosity over a wide range of temperatures, rather than thining out. The larger the number the thicker (higher viscosity) the oil.

The concept of the numbers goes like this. A 20w50 oil is really a 20W oil that has the hot characteristics of a 50W oil. In other words if you placed 20w50 in one pan and straight 50W in another and heated them equally at engine temps they would be the same viscosity, but at cool temps they would be very different with the 20w50 being more fluid.

Currently the thought is that some major percentage of all wear (75% or greater) comes during the first few seconds of running before oil is uniformly lubricating. The manufacturers say that the use of thin oils is the best defense for this problem; thus all multi-grade oils are better by this thinking.

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

If you are going to change the oil filter gasket and the lower oil cooler line I would recommend that they be done at the same time. Are you are going to do this in your driveway on jack stands? If so here is a few items that you may need. A good drain pan, a 100# bag of oil dry, a gallon of driveway soap, a bench grinder to grind a 24mm wrench down to hold the fitting in the filter housing from turning, a cut off wheel to shorten a 27mm wrench to turn the line nut with, a extra large bag of towells to wipe your self off. It may be a good ideal to get a new oil cooler and the other line just in case the treads on the cooler stay in the nuts. This can be really important late Sat. afternoon when you have a hot date for latter that evening. I almost forgot you will need to cut a 6mm allen wrench off very short to get the bolts out of the filter housing. Now if you can just make the tools that you need in 1/2 hour that would good.
Good Luck and let me know how long it takes you.

#1a I opened up the glovebox and found the temp and blower controllers. To find the defective element I checked for continuity between the monovalve and each plug pin. I found no connection, so there must be a open circuit between the controllers and the monovalve. Any suggestions?

#1b While behind the glovebox I found a disconnected wire. Its connector looks like the pin of an antenna but with a screw on cap much like that for the speedometer cable. What is this?

#1c I also found a hose line that has black rubber, but with a foam rubber connector hose, that just disintegrates to my touch. What is this and can I replace this foam with just regular hose.

#3 Sound advice from Corky. Again I had to laugh at myself. I have already spent too much time underneath the car trying to tighten up the oil filter cannister in attempt to effect a poor mans leak fix and now am in deep apreciation of the task at hand. One correction to Corky's advice, I needed the gallon of soap for myself. I did have a small success on the oil line. I removed the front of the lower oil line, slipped on some heavy duty shrink wrape, shrunk it down and hose clamped the ends of the shrink wrap. No need to use the other cars to get to my date. For some reason I now have a new leak from the front of the lower oil pan.

#4 Thanks for the great explanation on oil viscosities. I now have bought a good supply of 20W50.

Michael

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82 300TD Turbodiesal +250, 000
86 Volvo 740 GLE 220000
85 Honda Civic 120000

MBZflyer,

Have you completed your repairs to your oil leaks? The oil cooler/oil filter housing oil leaks is without a doubt, one of those proverbial can of worms.

When I prepare an estimate for this job I break it down in three parts, and each part gets bigger.
First, just the oil cooler. I mention that the threads may be ruined by taking off the cooler lines and then comes part two.
Second, add the oil cooler lines. But now the threads on the oil filter housing may be ruined by taking the lines off of it.
Third, add the oil filter housing fittings, and that is if they come out.

Part of the problem is getting the service advisor to understand the whole nature of the job, and the advisor explaining this to the customer so that the customer understands. And if the advisor or the customer is in a hurry, forget about it!!!

Now sometimes, I now digress, you have an under-achieving service writer who still thinks these cars have a carburetor and could not explain how to turn on the AC. Then everything is lost in the translation and we look like we are trying to rip off the customer and everyone is pissed off at each other.

Anyway, this is one of those jobs that you have to sit back with a cold drink, put your feet up and think to yourself, is this old diesel really leaking all that bad?? It is 15 to 20 year old car and it has an oil leak, but it is really that bad that the neighborhood kids are slipping on the oil trail that is in the street? Nah!

With an old car we can lower our standards when the aggravation of the repair is way higher than the benefits of the repair.

My two cents....

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Hi metricman,
I agree with what you say about the age of the car vs no oil drips. However my oil liines is leaking in the middle of the hose and thus my rupture anytime.

I friend gave the name of a shop she trusts and they quoated me 1.5 hours to change teh oil lines. I spoke with them by telephone and they to know their stuff and are willing to discuss the repair in detail. The name of the shop is Motorspeed West, in Santa Clara. I will let know how the repairs went.

I must order up a couple of oil lines from mercedesshop and I may also do the oil canister gasket and lower pan gasket while we are digging in that area.

Michael

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82 300TD Turbodiesal +250, 000
86 Volvo 740 GLE 220000
85 Honda Civic 120000

With the extreme possibility of the aluminum threads on the oil cooler fittings stripping out, there is one way which has worked for me each time I've had to get involved with this area of the car... Take your 27mm wrench and break the upper and lower connections loose with a sharp "snap". Now, slowly and carefully, as you're backing off the fittings, bo back and forth on each thread a couple of times with the wrench. Keep doing that until you've got the line all the way disconnected. When putting the lines back on, be very gentle and take it slowly when reconnecting. Make absolutely sure you start it square on the threads, and don't ovetighten when you're at the ends of the threads. With a little care, you can save having to stick a new oil cooler on there. It is to my understanding that the reason for the aluminum cooler body is that it dissipates heat better, although it'd be nice to have some sort of a steel jacket for the threads! Anyhow, my $0.02


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Rgds,
Aaron Greenberg
MB technician
Precision Motorcars, Cincinnati, Ohio
'67 250SE Cabriolet
'77 450SL
'80 300SD
'85 380SE
'89 420SEL
'93 300E 2.8
'74 Jensen Interceptor Mk.III
'81 DeLorean DMC12
'85 BMW 745i Turbo