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Defroster workaround

2008 Allegro Freightliner FRED ….

My defroster has quit working. Very little air flow. I’ve taken it apart as far as I’m comfortable with. Cleaned the hoses from the junction box. Additionally the dash A/C works only sporadically and we’ve paid for 4 hours of labor at the freightliner dealer only to have them tell us that they can’t find anything.
So….until I get it working, I just don’t drive it if I’m gonna need the defroster

Do y’all have any ideas for a work around? The first this happened, we DID need it and my wife just kept toweling off the windshield 🙂
Chip & Nancy (and our furry pack). 2008 Allegro Open Road Freightliner.

Have you verified the AC system 12 volt VACUMM PUMP is functioning and pulling a vacuum?. ALL Diesels require a 12 volt vacuum pump. This pump supplies the vacuum needed to operate the Dash AC/Heater blend doors. Also, the normal result of NO vacumm is default to defroster ducts. But, you year might be different and requires vacumm to move the doors. Doug

PS, this pump is located on the outside firewall and easy to see. They usually look like this link.

Then connects to the reservoir.

Just do a web search for 12 volt automotive heater defroster. There are plenty that plug into a lighter plug for less than 20 dollars.
2019 Horizon 42Q Maxum Chassis w/tag
Cummins L-9 450 HP / Allison 3000
2006 Jeep TJ and 2011 Chevy Traverse Tows

We had a problem with our blend door on a ford v10. It was a couple of bad vacuumn lines that needed to be replaced.

My guess would be the blend door is somehow stuck and sending the airflow in a different direction. Typically defrost also uses AC to remove condensation so that could also explain why your AC is sporadic - the two are related.

The blend door may be vacuum actuated (most likely) or cable (not likely).

If it were mine I'd take a look at the dash controls first to see if something has become disconnected or, given it's age, deteriorated and possibly leaking.
There are 24 hours in every day - it all depends on how you choose to use them.
Bruce & Jill Brown
2008 Kountry Star Pusher 3910

Explorer III
Explorer III
Well first I'd work at finding out why it's weak.
Blower issues?
Heater/AC/core clogged?
Vacuum motors not working? (The cans that pull/push the air doors/gates open and closed)

Meanwhile a fan blowing on the windsheld may help to defog.. Defrost however needs heat.> They make 'em with a 12 volt heat element but... That's gonna cost you amps
Home was where I park it. but alas the.
2005 Damon Intruder 377 Alas declared a total loss
after a semi "nicked" it. Still have the radios
Kenwood TS-2000, ICOM ID-5100, ID-51A+2, ID-880 REF030C most times

Explorer II
Explorer II
Back in the day it was normal to have fan mounted to blow on windshield.
I have seen small electric heaters that would work if you could run gen-set or inverter while driving.