I crawled around under the dash this weekend and found three big vacuum leaks--one of them was at the center vent element. Replaced it (what a hassle!) and fixed other loose rubber joints. Now blower and vents all seem to work properly. But, STILL NO HEAT!

To summarize:

--new servo
--replaced amplifier
--new aux water pump
--air purged from coolant
--tight vacuum systems
--interior and ambient temp sensors check OK
--temp selector wheel checks OK
--replaced foam tube in dash for cabin temp sensor

The blower did not come on (except in DEF mode) until coolant reached ~80 C. Still no heat in cabin--drove to work this morning with frozen fingers and toes.

__________________
1978 300SD 149K miles silver-blue "Maxine" (mine!)
1979 300SD 318K miles red "Helga" (SOLD)
1980 300SD 321K miles yellow "Linda" (younger daughter's)
1980 300SD 148K miles blue (SOLD)
1980 300SD 153K miles green(parts car, SOLD)
Yes, I have a W116 fetish :-)

Ed,

I assume all of the hoses are OK. Quite Frankly, with mine I had to ensure that all hoses lines running to and from the heater core were open and clear. To my suprise, I found a humungeous (sp)ball bearing that was shoved into one of the hoses to keep coolant from moving to the heater core. The mechanic said he did this to help "air conditioning" ---- idiot.

Also, flush the heater core. Although mine ran full through, there was a bunch of sediment and junk that came out when I ran a hose thru it.

JCD

What is the direction of flow through the heater core? Looking at the firewall, is it right-to-left or left-to-right?

__________________
1978 300SD 149K miles silver-blue "Maxine" (mine!)
1979 300SD 318K miles red "Helga" (SOLD)
1980 300SD 321K miles yellow "Linda" (younger daughter's)
1980 300SD 148K miles blue (SOLD)
1980 300SD 153K miles green(parts car, SOLD)
Yes, I have a W116 fetish :-)

I think, from left to right. I never really tried to find out definatively. It made sense to me to follow the hose from the aux pump to the firewall, that should be the inlet, the outlet goes to the block if I remember right. I just removed the hoses from both the inlet and outlet of the core and flushed it. That way I didn't move any of the junk downstream.....or downstream.

I did not flush the core with alot of pressure. I just used a nipple on the end of the hose and ran the hose on at just a tick of a turn...not full blast by any stretch of the imagination.

I also removed each one of the hoses and tested for flow using a similar procedure, hose in one end, open at the other. When I hit the hose with the ball bearing in it, it was like winning the lottery.....Bingo.

If you want to discuss, shoot me a private message with your number and I'll call.

JCD


JCD

Edblock,

On your list of things done I did not see work on the small control valve located on firewall (monovavle?) inside engine compartment. My heater would blow cold/warm intermitantly until I purchased a repair kit and fixed that valve. If you have one, you should definately check it.

Nic
'85 300CD

This car does not have a monovalve. It has the auto climate control servo a la Chrysler

__________________
1978 300SD 149K miles silver-blue "Maxine" (mine!)
1979 300SD 318K miles red "Helga" (SOLD)
1980 300SD 321K miles yellow "Linda" (younger daughter's)
1980 300SD 148K miles blue (SOLD)
1980 300SD 153K miles green(parts car, SOLD)
Yes, I have a W116 fetish :-)

...and flushed, and flushed the heater core. Seemed to have good flow in either direction. No large chunks came out, just rusty water/coolant and some sediment. All the hoses seem open and not leaking. I'm still thinking that it's the ACC amplifier because
1) it came out of my parts car so it's not new; 2) I opened the servo water valve by applying 12v and when I plugged it back in to the normal circuit it closed up again;
and 3) the aux water pump won't come on (unless I jump it to the battery)

So, I guess I'll buy a new amplifier and new temp sensors while I'm at it...

also, I have to replace the parking/emergency brake pads so the #*@% thing will pass safety inspection...will probably go ahead and do a complete rear-axle brake job while I'm in there.

__________________
1978 300SD 149K miles silver-blue "Maxine" (mine!)
1979 300SD 318K miles red "Helga" (SOLD)
1980 300SD 321K miles yellow "Linda" (younger daughter's)
1980 300SD 148K miles blue (SOLD)
1980 300SD 153K miles green(parts car, SOLD)
Yes, I have a W116 fetish :-)

Replaced the ACC amplifier and it still acted funny...then, I checked and replaced all the fuses and VIOLA! Automatic Climate Control! The A/C compressor comes on when it is supposed to, and everything!

Thanks to all who offered assistance and tips. Especially to Larry Bible, who faxed some info to JCD, and to JCD who faxed it to me.

__________________
1978 300SD 149K miles silver-blue "Maxine" (mine!)
1979 300SD 318K miles red "Helga" (SOLD)
1980 300SD 321K miles yellow "Linda" (younger daughter's)
1980 300SD 148K miles blue (SOLD)
1980 300SD 153K miles green(parts car, SOLD)
Yes, I have a W116 fetish :-)

Way to go Ed.

Glad to help,,,,,faxing only...Larry B is the real expert.

JCD