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bpu699 · 08-17-2024, 11:15 AM

2000 Winnebago ultimate advantage. Diesel.

I used to get a buzzing sound under the front drivers area that lasted 5 seconds on start up then stopped. Lately been hearing it turn on while driving for 10 minutes and shut off. Couldn’t figure out what it was. Don’t recall it doing that before.

Today the buzzing started, and stayed on. So, finally found the source.

There is a small electric vacuum pump in the front, behind the hood, that feeds a small 6 inch vacuum ball/reserviour. The air line to it had popped off. I put it back, buzzing stopped as vacuum pump went off.

What is this little electric vacuum pump for???

**Lt Dan** · 08-17-2024, 11:18 AM

It's to supply vacuum power for the HVAC controls in your dash air.

Skip426 · 08-17-2024, 11:21 AM

The vacuum supply for your Evans/Tempcon dash A/C controls .

bpu699 · 08-17-2024, 11:23 AM

Thanks for the quick reply! So if it runs more frequently would there be a leaking vacuum valve somewhere? I assume if it fails it goes into a defrost default setting?

HaloThere · 08-17-2024, 11:24 AM

My vacuum pump looks different so we may not be talking about the same thing, but I a vacuum pump in that forward compartment, that I think goes to the HWH air leveling system. I think you need it when the engine is off an you are trying to air-level you coach. (I think.)

bpu699 · 08-17-2024, 11:38 AM

Quote:

Originally Posted by HaloThere

My vacuum pump looks different so we may not be talking about the same thing, but I a vacuum pump in that forward compartment, that I think goes to the HWH air leveling system. I think you need it when the engine is off an you are trying to air-level you coach. (I think.)

My air pump is tiny, it wouldnt do much. HVAC system sounds about right.

Old Scout · 08-17-2024, 11:48 AM

Skip and Lt Dan nailed it. Unlike gas engines, diesels dont produce a vacuum [turbo charger], so you need an aux vacuum pump for the dash HVAC. Yup, big leak or pump fails, your dash HVAC defaults to defrost.