Defroster workaround

[beaubeau]

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 🙂

[dougrainer]

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.

https://www.summitracing.com/parts/smp-vcp113?seid=srese1&gclid=Cj0KCQiAofieBhDXARIsAHTTldpFMFNWHOg7...

Then connects to the reservoir.

https://www.amazon.com/Dorman-HELP-47076-Vacuum-Tank/dp/B000COB8FA/ref=asc_df_B000COB8FA/?tag=hyprod...

[chuckftboy]

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.

[gvisnic]

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.

[Bruce_Brown]

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.

[wa8yxm]

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

[JRscooby]

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.