No heat in the cab

[CRHardie]

A friend has a 90 D250 that has plenty of engine heat but no heat in the cab. The blower motor runs fine also. Is the hot/cold controled by a cable or is it vacuum? He said it worked fine last year. Thanks

 

[Greenleaf]

It's that li'll vacuum dashpot/control thinggy that is mounted to the inlet side of the heater core. Right next to the firewall. I suppose you'd have to test for a vacumm there and test the unit itself.

GL

 

[jrjuday]

The heater actually has two types of control. The push buttons for heat, vent, defrost, etc. are vacuum actuated, but the lever which controls air temperature moves a cable which appears to open/close a door in the heater. The problem could be a broken cable, or a broken pivot point. I had one break at the pivot point, I repaired it with JB weld (man's other best friend) reinforced with spring wire. Has lasted 4 years.

 

[bgilbert]

Try cancelling that gay vacuum actuated water valve. Remove it and replace with a new/longer straight piece of heater hose. Or if you want some form of water shutoff, say for colder AC in summer, get yourself a valve say from a big rig or do like I did and use a ball water shutoff valve inline.



Also drop down the glove box and verify the movement of the linkage of the hot/cold door by way of the temp control lever on the heater control unit/dash. Move the lever from hot to cold and see if the linkage moves freely.

 

[Phil Stuart]

Cab heat or lack there of

I did exactly what Bill did, removed the POS valve operator thats on the heater line and installed a 3/8" (I believe) ball valve with a couple of short pipe nipples cut to fit and VOILA! no problems now! I just found a way to cap the vacuum line with a barb fitting and a cap.



Phil