A/C and tacho problems
 

I have a problem with aircondition on my 190 2.5 diesel,when I start the engine the a/c starts normally but then it cuts down and never engage again.I took the car to a repair shop and he told me that he have to do an other relay with the klima relay.He done the relay and the a/c semms that it's working fine now.
Do some one here knows about it or is someone having the same problem?

The a/c problem looked solved with the relay that he done for me but now I have a problem with the revcounter(tacho),the tacho seems worked when ever he likes and some times goes up to 2 or 3 and down again,when I rev the engine.Is the relay not letting the revs signal passsing to the tacho,or there is an other thing that I might look at.

Thanks

I di not have a 190, but some one here that does should chime in...

Check the belt.

I believe that the speed sensor in the compressor will shut down the compressor if it senses slipping.

The a/c compressor stopped coming on and my tach was not working. After doing a little research on here I changed out my OVP relay and everything started working fine.

Newbe need help
 

Hi, I am new to this forum stuff and to my 300D.

I need to fix the tacho, it works intermittent and takes the AC out with it.

I have done a lot of reading in this forum and believe the tacho not working takes out the Klima stopping the AC clutch engaging.

I am not the brightest at times and have not found where the sender for the tacho is.

I have looked around the left side of bay looking for the amplifier , round black screw top but cant find it.

On the back of the injector pump is some sort of device with 2 wires that maybe a tacho sender?

I dont know where the Klima is either, i do have a relay for the AC but i reckon its only for the fan and is not the fix i have read about, but i aint sure.

I have a set of CDS for the 124 range but it does not cover the 1988 6cyl 300D, it covers the 87 turbo. Can some one recommend a good manual to buy i have emailed some O/S sites but dont get replies maybe cause i am in Oz?

I guess I have asked everything that is covered in other posts but please don't get peed at me I have tried to find the answers to my Qs but being a newbee have really just got more Qs.

Peace and blessings Steve

88300D,
It sounds like your OVP relay is also shot, I had the same problem on mine.

It sounds like your OVP relay is also shot, I had the same problem on mine.
 

Why?
Doesn't the OVP relay relate to the running of the engine? the car runs real sweet, so far at least. It is just the tacho AC issue.

Peace and Blessings Steve

For some reason this relay controls the tack and the AC. That's kind of the giveaway that it's this relay, when both of these go out at the same time.

Thanks would have never got that from the reading, do you know where i will find it? from threads know what it looks like and can purchase from MB dealer even if its expensive it will be nice to have it all work

It's behind the battery, it's a silver box with a red plastic top. There is a fuse on top that is probably blown, and you may get some more use out of it by changing the fuse, but it will keep blowing fuses until you change the relay itself.

Checked it out, fuse ok, will seek tacho sender

Steve:

Replace the OVP relay first -- it's there to switch the power off to the electronics if the voltage goes too high. When the relay fails, it's usually because of bad solder contacts inside the relay, so it will randomly cut off the power to all the electronics, including the tachometer drive.

The KLIMA relay for the AC measures the engine speed and the compressor speed, and will turn the AC compressor off if the engine speed doesn't match the compressor speed (this prevents a locked up AC compressor from breaking the belt. No belt, no water pump, serious overheat and cracked head, etc).

It is much more likely that the OVP is bad than that the tachometer pickup is.

I'll bet you also have intermittant idle speed variations, too.

Peter

thanks
 

Hi, i am very greatful to all who have tried to get me to the bottom f my woe.

it was indeed the OVP, today i removed all three relay modules Klima, ERL & OVP the all had cracked solder joints. the klima had many the ERL had one slightly suspect and the OVP had one obviously not making good contact.
The Klima and ERL are easy opens the joy of plastic, the OVP being aluminum is the most difficult.

this forum has been very useful and members seem to communicate well keep it up.

This thread has been great and has made me feel much better. I have an 83 300D; Does anyone know where my OVP relay is located? My tach is intermittent, and I believe it has also made my A/C stop working. Thanks in advance for any help!

Hi,
I have no experience with you model but on my ride it is behind the battery shield, that's the plastic bit behind the battery.

My OVP is the aluminium one with the knife-blade fuse on the top of it. It has a black plastic cover over the whole unit.

Hope this helps you.