Hi,

The Heat and A/C does not work on my 1990 300D(2.5TD). The blower motor does come on when I activate the blower speeds and the air that comes out is not hot or cold.

If I roll the temperature dial on the CCU all the way past 85 degrees, then it seems that hot air comes out to defog the windshield. If I roll the temperature dial in the other direction, the A/C does NOT kick-on.

I recharged the A/C with R134 last summer and it worked fine. I also already replaced the mono-valve and the auxillary water pump. Any recommendations would be greatly appreciated. Thanks.

Best Regards,
Louis

are you near NC??
I'm hosting a strip party of my vehicles to get them out of my yard... I have a 93, and a 90 124 for parts!!!

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Do you think that the problem may be the Climate Control Unit(CCU)? Are there other things I can test before replacing the CCU? Thanks.

Test the cabin temperature sensor's fan. There's a little vent next to the sunroof switch, it should be sucking air in.

There is also another important sensor mounted on the blower fan housing under the wiper motor. Don't think it goes bad that often though.

It's not unusual for the problem to be the ccu itself.

Is there a way to test the CCU? Thanks.

Will the blower come on when one of the manual fan buttons is pressed. If it does:

Cut a 1 centimeter square piece of paper and hold it to the small grille next to the rear view mirror while the key is on. If the paper does not stay in place, find and fix the sample fan. This fan draws sample interior air past a sensor.

If the fan does NOT come on, check the strip fuse under the hood near the master cylinder.

Hope this helps,
Larry

__________________
2001 SLK 320 six speed manual
2014 Porsche Cayenne six speed manual

Annoy a Liberal, Read the Constitution

The service manual has a good selection of documents in the climate control section that covers step by step troubleshooting of almost all of the components of the system. It can seem a bit tedious to go through the tests but when you're done you'll know if component X is working or not. Documents 83-604 and 83-605 are a good place to start. If you Google "124 83-605" you should have good luck find a pdf file on the web.

__________________
'82 300D - Light Ivory, 2nd Owner (Back in the wind April 2013!)

'95 E300D - White, grey interior. (Suffering from stuck/broken glow plugs)

Deuteronomy 22:4-
"Thou shalt not see thy brother's ass or his ox fall down by the way, and hide thyself from them: thou shalt surely help him to lift them up again."