Climate control/blower problems...HELP! - Page 3 - PeachParts Mercedes-Benz Forum

Brian Carlton · #31 12-16-2006, 03:41 PM

Quote:

Originally Posted by dmtinker

Ok, so today, I replaced the aux pump, the blower and the acc (ccu?). No blower....I suspect that the ccu I got from ebay is bad. I don't know what else it could be.

While the CCU can certainly be NG, the system uses a blower controller and a set of resistors to control the fan speed, in addition to the CCU. Either of these items can also be the culprit, although they are less likely to fail.

dmtinker · #32 12-16-2006, 08:09 PM

I've already replaced the fan relay. I did that first before I knew the system. I have not replaced the resistor pack but I really suspect the acc. Electronically, I don't think there's much more to the system......

mplafleur · #33 12-17-2006, 01:44 AM

The pushbutton unit doesn't directly control the blower motor. There is a tempperature control module by the passengers right knee that sends a signal to the blower motor module. The voltage of this signal determines what speed the motor is supposed to be at.

dmtinker · #34 12-17-2006, 03:53 AM

Yes, but regardless of the temp, I should get defrost blower. I believe its required as a safety issue. Am I wrong?

#35 12-17-2006, 10:18 AM

Quote:

Originally Posted by dmtinker

Yes, but regardless of the temp, I should get defrost blower. I believe its required as a safety issue. Am I wrong?

The defrost blower should work anytime you push the button, but a bad ACC unit can also prevent the defrost setting from working.

Brian Carlton · #36 12-17-2006, 11:00 AM

Quote:

Originally Posted by dmtinker

Yes, but regardless of the temp, I should get defrost blower. I believe its required as a safety issue. Am I wrong?

I believe that you are correct. Once you select defrost, you get maximum blower speed. The blower controller and resistors should be irrelevant in this situation......but......I'm not 100% positive of this fact.

Have you tested the new blower with 12V applied to the plug, after it has been installed..........just to cover your bases?

mplafleur · #37 12-17-2006, 11:09 AM

If you have a meter, you can check the voltage at the connector to the blower motor.

jim16671836 · #38 12-17-2006, 11:19 AM

Send me a email if you are interested in a remanufactured Unit... Part numbers are 126 830 02 85 ... jim16671836@yahoo.com If the unit helps you, then you pay for it and if it doesnt help you just ship it back.. I have 3-4 units with different part numbers for a 126.... Jim

dmtinker · #39 12-17-2006, 04:55 PM

The seller I bought from said he will cross ship me a new unit. I'll check the motor just in case.

mplafleur · #40 12-17-2006, 08:52 PM

You need to determine what part isn't working.

Start with the blower motor. You can either apply 12 volts to the connector and see if it spins, or check the voltage at the connector with the CCU in defrost mode.

If the motor works and there is no voltage at the connector, then the problem is either the CCU, the blower motor module, the temperature control module, or a fuse. I don't have any of the schematics in front of me to help diagnose any of these.

Magoo · #41 01-03-2007, 03:12 PM

Has anyone continued investigation of this problem?
I came across this thread recently through a search, after my car started blowing the #8 fuse-25A labelled heater blower. I think you guys were talking 126 dialect though, my 123 seems to be slightly different. It will blow a new fuse after 2-3 seconds, so it doesn't seem like it's a direct short. I have also proven the blower itself to be good on the workbench (20 amp fuse holds), and after consulting wiring schematics, unplugged the aux water pump but have not retested the circuit yet...

dmtinker · #42 01-03-2007, 05:57 PM

I've done some more investigation. I haven't been able to get into the car due to it being so cold here but here is what I found out.

The 82 W126 had a blower fuse for half the year, mine doesn't. I'll test the blower and see if it is getting voltage. I will let you all know what I find. If the blower is good and I'm not getting voltage, I think it can only be the push button, the blower controller (relay?) or the resistor pack. If there is a way to test each component, I would appreciate someone posting it.

mplafleur · #43 01-03-2007, 09:47 PM

Quote:

I've done some more investigation. I haven't been able to get into the car due to it being so cold here but here is what I found out.

The 82 W126 had a blower fuse for half the year, mine doesn't. I'll test the blower and see if it is getting voltage. I will let you all know what I find. If the blower is good and I'm not getting voltage, I think it can only be the push button, the blower controller (relay?) or the resistor pack. If there is a way to test each component, I would appreciate someone posting it.

If you have a meter and the where-with-all, there are two points you can probe.

The temperature control module has an output that goes to the blower module. This signal is proportional to the blower speed. Something like this (I'm making these number up) Less than 2 volts is off, 2-4 volts is speed 1 (low), 4-6 volts is speed 2, 6-8 volts is speed 3, 8-10 volts is speed 4, 10-12 volts is speed 5 and > 12 volts is speed 6 (high). It's probably something cose to that.

The pin number on the connector on each module is buried in the manual somewhere. I'll see if I can dig it up.

Quote:

I think you guys were talking 126 dialect though, my 123 seems to be slightly different. It will blow a new fuse after 2-3 seconds, so it doesn't seem like it's a direct short.

Some fuses are slow-blow. They can take several seconds to blow. But it does sound like the circuit is drawing a LOT of current.

Magoo · #44 01-04-2007, 01:19 PM

I was able to troubleshoot a bit more today. First I hotwired the blower with an ignition feed and an inline fuse. It seems to run at right around 15amps because a 15amp fuse held for several minutes and then popped. I put a 20 back in that line and then replaced the #8 slot in the fuse panel with the proper 16amp(the PO had a 25 in there), and with the aux pump still unplugged, started the car and tried the different pushbuttons. The #8 fuse popped again, but at least I have heat.
So I guess that narrows it to the pushbutton panel, the fan speed controller, resistor bank, and of course associated wiring.
Any comments would be appreciated.

dmtinker · #45 01-05-2007, 09:48 AM

Could it be that the motor is drawing too much? That's what I would suspect.

Anyway, I finally got under my dash to start doing some testing. The first thing I noticed was that the blower was unplugged.

.

I swear I plugged it in. I must have knocked it out when putting the cover back on. Needless to say I'm both embarrassed and pissed that I went with out heat for 2 weeks.