Hey all, in my continuing 300SD adventure, we have finally got the transmission and starting problems solved so we can go on to more important things...air conditioning in the south for the summer???
My a/c system only gives defrost (and damn well) but absoluting nothing when on the heat or a/c settings. No blower activity no temperature differential, NOTHING. Any ideas as to were to start? Ive read back a good ways on the forum threads and found nothing that sounds like my problem.

get at the blower motor plug.. check for voltage through all the settings on the control unit. it is important that you do this when the engine is up to temp, cause anything other than defrost should not work when the engine is cool.

if you are not getting any voltage then your CCU needs to be soldered up probably. if that does not work then you need the box under the hood replaced.

if you are getting voltage it might not be enough to get the blower spinning.

check and report back

__________________
-Trevor

OBK #12
1980 300SD 333,XXX miles - Totaled
1986 Mazda RX-7 212,XXX miles - impounded and auctioned off
2005 Jeep Liberty CRD Limited 33,000- SEGR, Provent, Fumoto

IIRC, your car also has the servo. Check that as well, and check all your fuses. Do you get and blower activity in any of the other settings? Does the A/C system have a sufficient freon pressure?

__________________
RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

90 Dodge D250 5.9 Cummins/5 speed. 400K

the freon pressure is further down on the list...i think his CCU is not making contact (unless it is working fine on the heat settings) if it is working on the heat setting then i'd check the freon pressure...

but i am assuming the blower is not working at all except for defrost as he said.

__________________
-Trevor

OBK #12
1980 300SD 333,XXX miles - Totaled
1986 Mazda RX-7 212,XXX miles - impounded and auctioned off
2005 Jeep Liberty CRD Limited 33,000- SEGR, Provent, Fumoto

Blower is not working on anything except defrost and at any engine temp. Turning the dial from heat to cool does nothing and and high to low makes no difference, but turn on the defroster and blower speed is great, and plenty of hot air. There was ice on my windshield this morning and the defroster had the whole windshield de-iced in a matter of minutes.

okay so you need to check out the blower first.. the plug for it is way to get to... passenger side of the car take the kick panel of it should be on the outside of the car right there

one thing at a time here.

__________________
-Trevor

OBK #12
1980 300SD 333,XXX miles - Totaled
1986 Mazda RX-7 212,XXX miles - impounded and auctioned off
2005 Jeep Liberty CRD Limited 33,000- SEGR, Provent, Fumoto

So did you ever get the issue of the blower motor resolved? My 1980 300sd is doing the same thing and I need help.

I know this post is super old but I will post for future seekers.

If your Climate Control does NOT work in any mode but DEF then the first thing you need to do is make ABSOLUTELY sure that you DO NOT have a Vacuum leak ANYWHERE.

The vacuum system on the W116 300SD is connected to just about everything. Making sure the vacuum system is leak-free is super important.

When I first purchased my 1980 300SD the A/C and Climate Control did NOT work. The door locks did NOT work. I meticulously went through the ENTIRE car and found disconnected vacuum lines under the hood and bad door lock vacuum switches inside the doors. I plugged in a replaced everything that was bad and it all works fine now. So many problems solved just by securing the vacuum system.

on car with the servo system you have to make sure there are no vacuum leaks. There is a switch under the dash that will turn the blower off if the vacuum supply drops.

__________________
1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg