84 300d No HEAT OH NO!!! And no Defrost even worse!
 

I have an 84 300d that the buttons do near to nothing. Once in a while I hear some kind of a vacuum sound (tsss- sound of air releasing) happen but If I press the buttons I get the blower to come on and sometimes I can get a breeze coming out of the vents when EC is on but never a strong breeze out of the defrost.

The other prob is this... when I'm going 75 on the interstate I can't get that car to heat up for nothing. If I'm going under 50 it'll get hot on EC but still no defrost. But if my speed is over 50 forget heat. That car's an ice cube.

Any clues...

for the heat, try this. warm up the car then shut it off. Before you restart, put the blower on high, GLow the plugs and fire her up. Thier should be heat then. If this happens this would indicate a bad monovalve. Thats how it is on my 240D, i havnt gotten a chance to fix it, and since i dont drive it in the winter, i dont worrie about it.

the warming up issue im unsure of. Someone else will comment, but my quess would be your T-stat working inproperly

Monovalve. Get a monovalve repair kit ($20) from Fastlane. Simple to replace. 4 screws. Pull out the diaphragm assm. Reinstall 4 screws. easy peazy. Japaneazy.

The "no heat at highway speeds" is definitely symtomatic of a torn monovalve diaphragm.

Thanks guys... I'll try the monovalve thing.

I agree the monovalve is bad. However, that doesn't explain all your symptoms. A bad monovalve would not account for blower problems. I suspect there is another problem also.

Try $44.00

Wow! :eek: Prices must have gone up since I last bought one. I bought one for only $20 about 4 years ago.

There are cheaper suppliers. Ebay for instance.

Also, many times you can call Phil, and the price he quotes is lower than what is on their online catalog, or he can get a little more competitive. If close, I try to support Fastlane. If not close, well, they should have been cheaper......:o

He's gotten smart.

This item had been $19.95 for years.

http://cgi.ebay.com/ebaymotors/Heater-Valve-Kit-Mercedes-Benz-300-d-cd-td-sd-123-126_W0QQcmdZViewItemQQcategoryZ33548QQihZ020QQitemZ300072830389QQrdZ1