'95 S420 with over 250K on the odo....fabulous car! All original engine, tranny etc....Talk about German Road Iron at it's finest!

Problem is no heat just on the driver's side. HVAC is the three block set up on the dash, not the one piece system found on later cars. Blower motor is fine.

Here's what I know:

1) Vacuum good from manifold
2) Vacuum assist good from backseat pump
3) Vacuum to/from a/c - tranny reservoir in passenger wheel well
4) All vents are working fine, however under high engine load air is being diverted to defroster....so we have vacuum problem...
5) Hot/Cold diverter working fine in center vent except as noted, no heat for the driver's side center vent.
6) Both heater core sensors are reading similar temps i.e. both match coolant temp.
7) Have not tested duo-valve for continunity, but if both heater cores are reading similar temps (#6 above), coolant must be being pumped...???
8) No apparent vacuum leaks from the floor board vacuum block.
9) No audible vacuum leaks from glove box vacuum block. Here I've not started pulling lines to test each line/acturtor with Mityvac. Honestly, I'm not sure how to pull these lines to test...afraid I'll break one. Do they just pull out or do they slide to wider opening and then out?

Possible culprits:

1) Heater actuator driver's side is leaking or has failed entirely. I have a schematic, but not sure which actuator number to test.
2) Vacuum block behind glove box is leaking
3) Electronic actuator switch for heat is bad
4) Drivers side climate/temp adjust is bad. Here however, all the flaps appear to be working when going from hot to cold in terms of re-direct of airflow just no heat.

Any help would be great appreciated!


One additional problem, squeek from rear just started...I think it's the shock, only makes noise when it's cold.


Best,

Wade

 

Update:

Continuity test on duo-valve was performed. Both valves had continuity.

Wade