Heat/ac help

[Hildebrand]

A friend of mine has a diesel 1987 sdl and it needed a ac evaporator. So I put the evaporator in and everything went smooth. My problem is that I wen to test the heat and ac and I am having problems. The heat doesn't get hot and only comes out of the defrost no matter what button I use. Now when I kick it over I ac it will work wherever I put it. What could I have messed up??


After messing with it for a
Little bit I couldn't get the blower to shut off no matter what button I hit. I had to turn the key off. Any help would be helpful

[vstech]

it could be the push button unit, (pbu) take it out, and open it up, and look at the bottom of the circuit board... if the solder joints have white circles on them, it needs to be reflowed. if it has burns on it, you may have a damaged aux pump...

[jay_bob]

Assuming the climate control functions worked before you took the dash apart, double check the following:

- Both cables plugged firmly into the PBU, and the left and right cables are not confused (not sure if they are keyed but just checking)

- Vacuum present at solenoid manifold under dash and all hoses hooked up

- Solenoid manifold plugged in

- Fuse F7 good, that is the source of power for the PBU/mono valve/aspiration blower/aux pump

[Hildebrand]

I got heat. Car was low on coolant. I am new to this car but the blower turns off everytime after about 10 seconds of turning the switch off. Is that normal? I can still only get heat out of the defrost and not the two middle vents.

[jay_bob]

That sounds like a vacuum side problem to me. If you have no vacuum at the 7 port manifold on the passenger side behind the glove box, then the PBU can't control the flaps, and it defaults into safe mode. Safe mode is max heat and all air out the defroster and blower on max.

Online service manuals for this car are free at startekinfo.com, look for chassis 126.

[rocky raccoon]

are active only in ac modes. If the vacuum controls are operating correctly, you will never get heat from them.

Sounds like your hvac is working fine.

[The Gears]

A question for the Raccoon.
I always have some air coming through the defrost vents, even when air conditioning.
This reduces the flow from the proper vents. Is this a leaking vacuum pod?
Question 2. The AC compressor clutch snaps on when I select defrost.
Is this a setting problem or a shot button control box?
Thanks

[jay_bob]

Question 1, it could either be the pod going bad or the foam rubber deteriorated on the edge of the flap. The result is the same, the defrost flap won't seal shut.

Question 2, The compressor will normally be engaged for defrost at above freezing temperatures. This is so that the air directed at the window can be dehumidified. You need to get the dew point of the discharged air below the temperature of the glass or it will fog up on the inside.

[rocky raccoon]

what he said

[The Gears]

Thank you gentlemen for your prompt and learned reply.
Where is that door that needs to needs re foamed and can it be accessed easily?
If a pod witch one?
Thanks

[jay_bob]

The defrost pod and door I believe on your car can only be accessed by removing the dash.

Best bet is to check out the online service manual, it has a very detailed description of the operation of the ac system and where all the doors and pods are.

startekinfo.com, click on MB Workshop Resources on the left side, page through until you find Chassis 126 manuals.

[Hildebrand]

Thanks for the replies guys. I am going to look at what you guys said tomorrow. Thanks again and I'll let you guys know what I find.