I just bought a 1987 300 SDL with 96k original mile! I hope thats good, excuse my ignorance but I am very new to this MD Diesel arena!
I am having this problem, the RPM does not work and the A/C does blow air but not cold, and the center vents blow very little air. I got this guy to check, and it seems that there is Freon too?? I read somewhere that this RPM and A/C problem may very much be related?? is that true?? Would could be causing this problem??
I think I noticed that some part is missing from the car, maybe a relay or something, its between the 2 firewalls on the drivers side in the engine compartment. Can anyone send me a pic of what that area should look like?? I would really appreciate anybodys help in this matter.
Please send me a PM so that I know I have a reply if you can.
Let’s assume the ACC pushbutton unit is working and the refrigerant level in the system is at normal pressure. You may have a problem with the Klima relay (part number 0035452605) or the 105C/115C switch at the front of the engine (where the upper rad hose connects to the engine). If you pull the switch and the AC comes on, then the relay is ok. If not then the relay will need to be repaired or replaced. Sometimes the electrical contacts in the relay can be cleaned.
You are correct in that the tach works off of this relay (no tach amp, per se) as it senses engine speed for proper compressor operation, such as shutting off the compressor at certain engine rpms, etc.
I noticed you also have a 300 SDL, I just bought one, its 87 with 96 original miles! I have a slight problem, Since I bought this car from an auction, it seems someone has pulled out a part, it seems its the OVP relay which is supposed to be between the 2 firewalls, I guess its supposed to look like a Silver piece with an orange top with a 10a fuse, there is also another piece next to it which looks like a flat piece of plastic and a few holes in it probably about 12-16, I am not sure if anything is supposed to go there??
Would you mind sending me a pic of that part of your car so that I know what it looks like??
This seems to be causing the problem of my Tacho not working and the A/C not working, my ABS light is also on. What I did was, I went to a salvage yard and picked me a relay OVP, ofcourse it was from an old car 87 300D, I am not even sure if this is supposed to work in my car or not, and it was making some noise when I shake it, anyhow, I picked it up for $10, I figured it would not work, I out it in and start the car, the light went off and the tacho worked and the engine ran a little different!! a lill smoother, but after running for a few minutes, it made an erratic jump in RPM and the ABS light came on and the engine started sounding a little diff, the tacho also stoped working, do U think the OVP was bad??
Gosh, thats alot of text for you, I am sorry, its just coz I am very new at all this, I would really appreciate your help.
Hey, I see by your area code that you're a fellow Houstonian. The car you're describing sounds like I car I once took a look at. Does this car happen to have a light blue exterior and dark blue leather interior?
-Joe
__________________
1981 300SD DB881 ext./code #236 leather int. aka: thistle green ext./olive int.
1982 300D, DB877 ext./code #135 mb-tex int. aka: petrol green ext./creme int.
No, actually this car has a Silver exterior, with Burgundy/red interior.
Can anyone please send me a pic of the OVP relay ON THE VEHICLE?? coz U see, mine is missing and there is another part right next to it, which is empty, I dont know if anything is supposed to go there or not??
Here is the update, I have founf out that my car is missing 2 relays, the OVP and Refregrant compressor and cut off relays. Its supposed to go infront of the drivers side between 2 firewalls. I went to a local salvage yard, picked up both the relays.
I am having an intermittant affect, ie I am having the problem of ABS light ON, RPM (tacho) not working. But after putting the OVP, the engine revvs differently suddenly when I go onto a pot whole or a bump, sometimes not all the times, and this causes the ABS light to vanish and Tacho to work! But still the A/C blows hot air. I am really really getting confused now.
Like I said in my previous post, the missing relays have already been replaced, and now the ABS & Tach work intermitantly, ie sometimes when I go over a pot hole or if there is a sudden jerk, the tach works and so does the ABS ligh (it goes off) but the A/C never seems to be blowing cold air???
WHat should I do???
BTW, any idea where I can get a repair manual for this car?
Linear Mode
