Heater Problems

I am still guessing that it is the filter.

 

I'm thinking your diagnosis is right on.

 

I've seen seperate valves for each heater.

 

That is the way my Pete is setup. Valves for cab and valves for bunk.

 

Freightliners have seperate valves for the front & rear.

 

If it was the filter it wouldn't allow much air but would still blow some out, it would still be hot.

Does FL's even have filters in them from the factory? I have yet to find one on my FLD.

 

Les
Get off that fat walet of yours and buy a Pete
Then you can have a filter

 

It's the temperature door. Look where your heater hoses enter the firewall. On the other side of the firewall is the heater core. The temp door will be right beside the heater core duct. Not sure on that truck but some have a cable and some are vacuum operated with an actuator valve. Since it's a big truck it might operate off the truck air.
That said most likely that actuator is bad. Kind of looks like a vacuum advance actuator on the side of an old distributor. You'll either find that or a broke lever where a cable hooks up.

It should be under the glove box area. You might even have to pull the glove box to see it. If it was an line loose, you would hear it.

Get to diggin, lol.

Make sure there isn't a second outside valve first.

 

I got rid of the fat wallet and just started to have the Brinks truck just follow me around...

 

To add alittle to what Condo is saying.... Flip you dash switch from heat to defrost to A/C, listen for the doors to flop open and shut.

If you system is like the older trucks you will hear them. Condo might know for sure, as my truck is older.