Heater Question(s) 1985 300TDT - PeachParts Mercedes-Benz Forum

jerryyoung · #1 11-10-2003, 05:30 PM

I had no heat when driving on the freeway, some around town. Heeding the advice posted on this great forum, I checked the monovalve (bad, installed new kit), now have heat at speed

. Also, checked auxiliary heat pump, not running

Checked for power with my trusty DMM, have power. Checked thru the motor, no reading

I guess I am lucky as I have read where a shorted pump motor takes out the ACC. My question is, has anyone rebuilt the pump motor or is it a "sealed" unit or is it not worth the effort and just replace it?
Thanks
Jerry

lrg · #2 11-10-2003, 06:13 PM

I took mine apart to try to fix but I found it had gotten water inside and the corrosion made a repair hopeless. It's not hard to take apart so it might be worth a try. Maybe you'll get lucky and find a simple problem. Given the downside potential if it shorts out I'd suggest you wire in a fuse while you're at it so at least you'll have a bit of protection in case your repair proves to be "temporary."

Peyton300TD · #3 11-10-2003, 11:23 PM

I have the same problem. PLENTY of heat around town. but on the highway, it's almost as if the cold wind overwhelms it.

jerryyoung · #4 11-11-2003, 11:17 AM

LRG - thanks for the reply and suggestion re an inline fuse.

Eric - when I pulled the top off the monovalve the problem was apparent, the small diaphram was torn loose from the piston. Very easy fix

Question - does the 240D have the same auxiliary pump? I have access to some 240D's but no 123's. I would pull the pumps and check on the bench for excessive current draw, I believe someone posted here the pump motor should draw no more than ~2amps?

Thanks as always
Jerry