My a/c blows cold & seems to work, fan blows good and strong for a while.

Thermostat (if it has one) seems to slow the blower down intermittently but doesn’t seem to be keeping the air temp in the cabin right.

Couldn’t figure out if it is the vacuum check valve, thermostat (if it has one) or something else?


thanks

Check that the aspirator blower for the cabin temp senor is working properly. With the ignition on the suction from it should keep a piece of tissue sucked to the temp sensor grille.

-J

__________________
1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

There is a procedure in the factory service manual (on startekinfo.com, go to workshop resorces, find the 126 chassis in the table) for checking the ac function.

It calls for a special breakout box to test the two big connectors on the CCU but if you read between the lines in the procedure, it will tell you the pins on the connector itself that the various thermal sensors connect to. You can read the resistance on the various sensors with a multi meter.

I suspect you have a bad sensor so the controller can't regulate.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

do you have any diagrams or good links that show were those parts are.

the star teck site seems to have manuals for everything but what I need

The blower is mounted inside the dashboard near the glove box.

The temp sensor is behind the grille on the dome light, by the sunroof switch.

-J

__________________
1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

thanks

now a truly newb question.

I know my motor oil is suppose to be type c

what about my antifreeze - red, green, ?

The factory coolant is yellow, it is Zerex G-05 in a bottle with a MB logo on it. Many parts stores have it.

-J

__________________
1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

thanks

okay I think I got all the vacuum lines working, cause it will keep a constant high flow blowing.

but it's not cold enough still.



can I simply buy some Freon and recharge it?

if so how do I tell what kind of Freon I have?

Take a look at the fittings on your AC hoses and compare to the diagram below.

__________________
Joe

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1980 300SD - 495k miles - 'The Ambassador'
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Former Family Members
95 C280
73 280SEL
90 300D
87 300SDL (X2)
86 560SEL
84 300D
80 300SD

I was wrong, I thought the temp sensor grill had air flow but it does not.

which vacuum line controls it?

edit: or rather which one goes to the ccu

Attached Thumbnails

 

and looks like I have r12

what's this part

edit: was replacing vac hoses and found it?

Attached Thumbnails

 

That's the vacuum valve that softens shifts when the coolant is cold.

-J

__________________
1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

is it on this diagram?

Attached Thumbnails