I have a 86 300E w/ 187k miles...It has a production date of 10/85, so not only is it the first year for the 300e in the US, but it was one of the first build....I have owned the car for about 5 yrs and it has 116k miles on it at that time.....

Problem....The dreaded "CLIMATE CONTROL" .....

The Fan Motor and Squirrel Cage along w/ the Fan speed control where replaced just after I bought the car..(5 Yrs ago)..

The last A/C service was done 3 yrs ago, the system was down about 1 lb....No leaks at that time were noted...

NOW TO THE PRESENT:.......About a couple weeks ago I noticed that the A/C was not working, so I took it to the local 76 Station and they did a A/C service they stated that the system was down about 1lb, after the service was complete they noticed that the compressor would not come on unless the power was supplied directly to the clutch....They wanted 2 hrs at $80. ($160.) do do the trouble shooting......several hours later and them conversing w/ another shop they final ly threw their hands in the air and said they did not have the knowledge or the tools to diagnosis the problem, but the best they could guess it was the Push Buttom Unit in the dash and because they could not say for certain they did not charge me the $160......They suggested that I take the car to the dealer.....Well 1 hr of diagnosis at $119. later they stated that it was the Push Button Unit which new was $530 plus the labor to put it in another $200.....I declined and bought a rebuilt unit off the web.....I installed the rebuilt unit and there was no change.....I have ck'ed the Aux Pump and it draws about .65 amps...I have also taken the Mono Valve apart and cleaned it (is there suppose to be coolant in the piston and coil area ???) I didn't think so, so I have a new mono valve, but have not installed it yet.....I have the CD shop manuals for the 124 and I have been tring to follow their test..I have done the first 7 tests of the 21 test under 83-604 , but now I don't know how to do the other 14 because I don't have the test equip....Any suggestions...I have also done the first 2 test under 83-605, I started out w/ power to boths sides of the low pressure senors but then I lost it...It seens like I have a current draw and that the Push button unit goes into hibernation after a certain time frame...In lui of not having any voltage I have been cking the wiring for continunity and they all ck out fine.....OOOH on the first 7 tests I had open circuits on test 3, the evap temp senor and on test 5, the coolant temp senor...All the rest of the tests were good, well atleast the ones I could do..........So HELP.......

Hank

I do not know if that is your problem but, it may help you sort things out.

__________________
J.H.
'86 300E

J.HIDALGO

I TOOK YOUR ADVISE AND DID A SEARCH OF PAST PROBLEMS AND I CAME ACROSSED A POSTING BY "YOU" (OF 03-10-2003) IN WHICH YOU HAD ABOUT THE SAME PROBLEM, I PRINTED ALL THE PAGES AND REPLIES BETWEEN YOU AND "STEVE BROTHERTON"....I WAITED A DAY OR SO AND NO ONE ELSE POSTED ON MY PROBLEM, SO I SENT AN E-MAIL TO "STEVE" AND HE GOT ME STARTED...FIRST I NEEDED TO DECIDE IF IT WAS THE "PBC UNIT" OR MAYBE THE "KLIMA RELAY"....DID A VOLTAGE CK AT BOTH SIDES OF THE LOWER PRESSURE SWITCH AND BOTH W/ THE A/C OFF AND THE A/C ON.....MY RESULTS WERE 12V ON BOTH SIDES OF THE PRESSURE SWITCH AND 12V FOR BOTH A/C OFF AND A/C ON.....STEVE SAID TO CK FOR A "SENSOR" PROBLEM...I HAD ALREADY CK'ED THE SENSORS AND HAD COME UP W/ OPEN CIRCUITS ON BOTH THE B-13 COOLANT SENSOR AND THE B10/6 EVAP SENSOR....I WENT BACK TO THE 2 SENSORS AND ON THE EVAP SENSOR I TOOK IT OUT AND RECK'ED IT W/OUT THE WIRING AND IT WAS OK...THEN I CK'ED THE WIRING AND IT WAS OK...SOOO I PUT THE EVAP SENSOR CIRCUIT BACK TO GETHER AND REPOSTIONED THE WIRING IN ITS CORRECT PLACE AND EVERYTHING CK'ED OU OK ONCE AGAIN.....HOWEVER THE B-13 COOLANT SENSOR WAS ANOTHER SITUATION....I FINALLY FOUNF THE RIGHT WIRING DIAGRAM....EVEN THOUGHT MY 86 300E HAS A PRODUCTION DATE OF 10/85...MY WIRING SYSTEM FOR THE ACC IS FOR THE 124.030 STANDARD VERSION UP TO JULY 1985....THAT SHOWS A B-13, 1 POST COOLANT SENSOR...THE GROUND IS ACHIEVED BY THE BASE OF THE SENSOR IN THE ENGINE....I CK'ED THE SENSOR AND WIRING TOGETHER AND GOT CONTINUITY...BUT MY JOY WAS SHORT LIVED, BECAUSE I THEN DISCONNECTED THE WIRING FROM THE SENSOR AND ALTHOUGH THE B-13 SENSOR CK'ED OUT OK THE WIRE THAT SHOULD HAVE SHOWN AN OPEN STILL SHOWED CONTINUITY....I HAD A SHORT???...I CK'ED ALL THE OTHER WIRES IN THE SAME BUNDLE IN THE THOUGH THAT I MIGHT GET A READING AND I DID THE FOR THE "HALL'S SENSOR" SEEMED TO BE CROSSING THE AND I COULD READ ABOY 2.5K OHMS....THE COMMON THREAD HERE AS I SEE IT IS THAT BOTH OF THESE CIRCUITS (SENSORS) GO THRU OR COME IN CONTACT W/ THE DASH POD CIRCUIT BOARD......A COUPLE MONTHS AGO I HAD MY KEY INIGTION WAS REPLACED AND ALONG W/THE LIGHT BULBS IN THE DASH POD....NOT I HAVE TO DECIDE IF THERE WAS A PROBLEM WHEN THEY PUT EVERYTHING BACK TOGETHER OR IF THE IS A PROBLEM W/ THE DASH POD CIRCUIT BOARD OR IF I HAVE COMPLETELY TAKEN A WRONG TURN???......

SO ANY ONE WHO HAS HAD THIS TYPE PROBLEM OR MIGHT HAVE AN IDEA OF WHAT TO DO NEXT I WOULD I WOULD APPRECIATE YOUR INPUT..

THANKS

HANK 86 300E
90 VOLVO 240
90 HONDA ACCORD EX

I put this posting on 05-18-2003 and so far I have got 3 responses and 2 of then were from me.....I thought a nice ACC problem, on a 86 300e...124.030..would bring out a few people, some that know what they were talking about and some that didn't have a clue....True an ACC problem has alot of ups and downs (tempature Pun)...and might not be as exciting as a discussing of what weight oil to use in a 123...but????.....I did notice as I did my search for related threads that they were many postings that had tought, but important questions and NO ONE RESPONSED...Oh well maybe next time......

I had the same problem, I checked everything and then finally read a posting that mentioned the temp sensor where the radiator hose goes into the top of the engine. There is a 2 post and a one post connection on the same sensor. I disconnected the single post and the a/c compressor kicked back on. I hope this works for you, I have been going nuts trying to figure this out for the past 3 weeks.

Tom

Tom

Thanks for your post....I was just out working on my 300e....My problem was the Evap Sensor (B10/6)....I was reading an open, so I took the sensor out and it ck'ed good and so did the wire...I don't know why or what I did to correct the problem I can only guess that the wire was pinched when the lower dash assembly was re-installed after I had the ingition switch replaced an couple of months ago...it was still winter and I didn't need the A/C..and therfore didn't notice the problem til it got hot here in the Sacramento Valley....I still don't understand why I was having problems w/ the reading on the Temperature Sensor (B13)...I think the green wire from the PBC unit goes to the instructment panel first and then to the sensor in the block....But to make a long story short I reconnected the PBC unit and my compressor kicked right in and started blowing cold air.....Yeah!!!!!!!!....

I don't know about 560'S but the 2 and 1 you are talking about sounds like the S25/5 switch..I think that deals w/ the engine temperature getting too high and the N6 control unit will cut out the compressor til the engine temp drops to a certain level...I couldn't quite tell from your posting if you had solved your problem..I hope so....

It would be nice to have another source of info that explains the theory a little better...especially on the Climate Control.....I have the CD for the 124, Alldata thru the internet and the M/B E-Class Owner's Bible fron Bentley press...Each one has some thing in it the others doesn't...But still it would be nice to have a source that explained all the characters and the plot of the story...

Hank
86 300e
90 Honda Accord ex
90 Volvo 240dl
90 Dodge Dakota 3.9

Im glad you solved your problem, I solved my compressor problem with the sensor wire I was talking about but in the process I shorted out my fan control by jumping connections during testing. Now I have to buy a climate control switch.

Tom

Tom,

I have a 560sl as well and just finished replacing a bad a/c compressor. New compressor won't kick on even if I jumper the low pressure switch. Sounds like I might have a problem with the temp switch as well. Did you replace the three wire switch and does the a/c now work? Also, how do you blow your climate control switch? I defininently want to avoid doing that!

Thanks,

Steve