hubertt

Hi Guys, I hope you can help me out with this problem before I put "FOR SALE" on this car.
My car is a 2001 C180.

The A/C has not been working for days now, I finally found the fuses diagram and went to check the fuses. I found out fuse#51 was blown, fuse#41 is okay. Replaced #51 ,turned A/C on and then again,"POOF!!" fuse blown. I don't know if the first blown fuse was original but it was a 7.5 A fuse.

Any ideas of where to check? Is there maybe a Relay in this system for A/C

hubertt

Was just thinking of something....... I still have to replace the thermostat, does this affect the function of the A/C ??? I wonder....since the A/C problem started together when the message of the "COOLANT" appeared . Are these problems related to each other???

Glyn M Ruck

Fuse 51 is 7.5 Amp. Fuse 41 is 15 Amp. There is no clutch on these aircons - only a pump actuator & the blower fan & engine fan + residual heat unit on some vehicles. The engine cooling electric fans share fuse 51. Make sure that the electric fan/fans are not stuck. You might have a blown cooling fan. Will post & come back - I see you on screen - I just want to read your other thread again

Glyn M Ruck

What is the engine temperature doing now? does it still stay too low. I'm confused - because if the electric radiator fan does not come in I would expect the temperature to rise??? Fuse 41 carries the blower fan & heated rear window & other devices which is why it's 15 amp.

hubertt

First I need to say ....Glyn Thank you so much for taking some time to help me out.....
Ok..... Fuse 41 is 15A ??? I saw fuse 41 is only 7.5A here. The engine temperature rises moments when I'm driving. It does pass the 80 degrees. Should I try to change and put the 15A fuse instead in #41???


It's getting interesting.

hubertt

I went and changed the fuse#41 to 15A and I still get a blown fuse#51 everytime I replace it.

Glyn M Ruck

You are going to have to check the electric engine fan/fans - some cars have 2 - to see if it is a dead short. Do you have a meter?





Sorry for delay - I had a business teleconference

hubertt

Yes, I do have a meter, where should I check?

Glyn M Ruck

I'm not sure where the plug is. You are going to have to follow the wires from the fan back if there is no plug/connector on the fan

hubertt

Well, I think it has to be the cooling fan, since the fuse#51 was blown without even turning the A/C on. I just switched the car on an POOF.... fuse 51 is out again. The fab motor will have to be replaced or rebuilt or what do you think?

I left the car on for 5 minutes and the fan doens't switch on at all.

Glyn M Ruck

Those fans will only come on when required and the temperature in the radiator or condensor get high enough. There is a temp sensor in one of the pipes. Try & put power direct onto the fan with a piece of wire to see if it works. Unplug it from the system first!

hubertt

I had to take out the fan completly but, there are 4 wires going to some sort of control module. I really feel like after this one I can apply as a MB mechanic :-)

Glyn M Ruck

Yes - its a variable speed fan. The control module varies speed as required.

hubertt

Well.... The fan's been tested and it's not working.... when I touch the wires the only thing it does is spark, like a Short Circuit going on. So, what's the veredict here??

Glyn M Ruck

Verdict sounds like a blown fan motor I'm afraid. Please do one thing for me. With the fan unplugged. Put a new 7.5 amp fuse in 51 & power the car up. See if it blows. Let me know

hubertt

I put a new fuse in 51 and it did blow when starting up..... huh??? it's getting scary now.

Glyn M Ruck

Oh crap - What now - Do you have access to an OBDII scanner? We need to read the codes on this car before we go further. We are missing something here. You only need a cheap one like this - must be CAN compliant. About 50US$ at Harbor Freight - Sears, Kragen, Parts America etc all sell. The plug is under a flap below the steering column. I'm sorry - from a simple thermostat this thing is being a pain but we will work it out. If you put your meter across the fan contacts is it a dead short or open circuit?

hubertt

I'm not really sure about the open or dead short, but I guess it's a dead short. As for this scanner I'll surely go get one.
I was also thinking, how about the temperature sensor gone bad ???

Glyn M Ruck

Does your car have factory Bi Xenon headlights or electric headlight adjustment? Does it have a coolant recirculation pump for the heater? These are the only other items that use fuse 51 & could cause it to blow. I really need codes.

Glyn M Ruck

Yes I also wondered about the temp sensor. As I said above it's mounted in a pipe. Check that - no harm done. If it's the temp sensor there should be a code stored

hubertt

Electric headlight adjustment.... and well I've just ordered the OBDII scanner. I guess I'll just have to wait to for the mailman to bring it. Otherwise I can also go to a garage and let them do the scanning. I'll definantly let you know.

Once more.. Thank you so much for your time and patience. I REALLY apreciate all of this help.

Glyn M Ruck

No problem - I'll let you know if I think of anything else - Check the headlight adjustment & coolant recirc pump if your car is fitted with one - I'm not sure on C180 - just to make sure that they are not contributing to fuse blowing. Good luck

hubertt

Something funny happened today...... remember I had this issue with the thermostat?? Well..... this morning I went to start the car and the message has gone.... I restarted the car to verify and ....no COOLANT message anymore. So what's the thing about these cars?

I went to test the voltage at fuse 51 and it reads 14.01V. Is this normal? The voltage at the Fan wires read 12.97V , but whenever I put a fuse in 51 it blows

Glyn M Ruck

Yes 14.01 would be a healthy fully charged battery - The alternator puts out max 14.1 volts.

If the car continues to run cold that coolant message will come back. It might have been the fan that triggered the message. I'm worried that if the fan has blown that it might have blown something else. That's why we need those codes. I want to know if we have more than a P0128 stored.