a/c htr vents

[mtemart]

I have a '89 760t wagon.
I only get air from the side dash vents right next to the doors. I have the EEC and get no code violations when I run the self-diagnostic test. The blue light never blinks, it comes on and stays constant until I push to turn a/c off. The a/c is working very well, the blower motor works on all settings, including off. The htr produces ample heat.
I have replaced the faulty vaccum valves and vaccum hoses as deemed faulty.
I think what I need to know is:
1)Are the dampers vaccum operated or motor driven?
2)What/how do I access an area so I can see the dampers?
thanks
marty

[billofdurham]

They are vacuum operated. The only way to get in to see the dampers is to go under the dash. If they are working then you should hear them as they move and you will hear a muffled thump as they reach where they should be.

You have replaced faulty vacuum valves and pipes so you know where you need to look. Are you sure you are getting vacuum at the Solenoid Vacuum Valve Assembly (SVVA)?

Whenever there is a suspected vacuum leak you should start by checking the vacuum supply hose in the engine compartment. Under-dash leaks are not so common. The vacuum hose for the heater can be found under the intake near the transmission dipstick tube. It is a 1/8" diameter white plastic hose. It goes from the bulkhead (firewall) near heater hoses to a tee with a check valve that is connected to a larger hose which is attached to the intake. It is common for the hose to rub through from chafing. If you find a leak cut the hose and splice in a small piece of vacuum hose.

Still in the engine compartment check the hose coming into the car near accelerator pedal which could be disconnected or damaged

Moving inside the car and under dash find the other end of that same hose. It can get crushed above and to the right of accelerator pedal. If necessary it can be repaired by splicing in a piece of rigid tube similar to that that comes on aerosol cans.

Now follow the vacuum line to the SVVA checking for leaks.

At the SVVA check the floor/defrost diaphragm for a leak. This is the yellow hose on the driver's side end of the SVVA. Plug it up with something and see if it returns to working. If it does then leave it plugged as the cost of repairing it is high. The reduction in function is minimal as it will only reduce the air flow to the floor.

Finally, the attached is from a Volvo publication for the heater system on the 760. I hope it helps.

760 ECC.pdf

(5.38 MiB) Downloaded 70 times

Bill.

[mtemart]

Thank you so very much for the advice.
I'll keep you posted...
marty