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Topic: vacuum pump cut off switch (Read 615 times) previous topic - next topic

Re: vacuum pump cut off switch

Reply #1 –
Bill and Sue, what would one use that for?
Richard & Betty Bark & Keiko our Golden Doodle
2003 U320T 3820 PBDS
Build # 6215
MC # 16926
2016 Chevrolet Colorado 4X4 diesel

Re: vacuum pump cut off switch

Reply #2 –
I think it is what is shot on our coach. I may be wrong but it probably shuts off the vacuum pump that actuates the different dampers in the dash. The dampers are vacuum operated to switch air flow from floor to defrost to mix. It must shut off the vacuum pump when vacuum reaches a set point in the switch.
Now I've got to find it when I get the coach home.
Nitehawk,  Demolition Lady, & our NEW master, Zippy the speeding BB cat.
1989 Grand Villa 36' ORED
Oshkosh chassis, 8.2 DD V8
2006 Saturn Vue AWD

Re: vacuum pump cut off switch

Reply #3 –
Quote from: nitehawk –
I think it is what is shot on our coach. I may be wrong but it probably shuts off the vacuum pump that actuates the different dampers in the dash. The dampers are vacuum operated to switch air flow from floor to defrost to mix. It must shut off the vacuum pump when vacuum reaches a set point in the switch.
Now I've got to find it when I get the coach home.
correct  nitehawk !!
93 U225 12v 5.9 
06 jeep toad

Re: vacuum pump cut off switch

Reply #4 –
Yup, just follow the vacuum line from the pump and it will lead you to the switch.

Pinching off the line from switch to dash HVAC control will tell you whether you have a leak or issue with the switch-- if it shuts off with the line pinched/plugged, then likely a problem with a connection, a vacuum door or the dash controller.  If the pump does not shut off, even at high vacuum, it is the switch.  If the pump just keeps running, but does not generate much vacuum, the pump is the issue.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: vacuum pump cut off switch

Reply #5 –
Hey Brett, what would constitute high vacuum? I checked over on the pass side up under the dash and the individual diaphragms actuated their respective louvers in response to the selector buttons. Maybe I do merely have a weak pump.

Thanks,
Norm
Nitehawk,  Demolition Lady, & our NEW master, Zippy the speeding BB cat.
1989 Grand Villa 36' ORED
Oshkosh chassis, 8.2 DD V8
2006 Saturn Vue AWD

Re: vacuum pump cut off switch

Reply #6 –
Norm,

I have never put a vacuum gauge on the system.  So do not have a number for you.  As a test (no idea if this would be definitive), remove the vacuum line from the switch.  Use either a vacuum pump or suck on it and see if the pump cuts off.  Just another test like pinching the vacuum line to the HVAC controller.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: vacuum pump cut off switch

Reply #7 –
Talking about vacuum...Back in jan, on my maiden voyage. I had no dash heat and the hvac was stuck on deforest could this be my issue . are is their a hot water shut off some where. one good thing is that when i move the switch to ac. the ac compressor engages...and thats a good sign  ^.^d   
1992 U300 Anniversary Edition wrong color DDC6v92T Big step up from my 1983 35' fc Blue Bird .

Re: vacuum pump cut off switch

Reply #8 –
Symptom, the vacuum pump runs a lot. The first thing to do with a problem in the vacuum system is to move the  lever on the Ford AC/heater control about a quarter to a half inch to the right from the stop. If the vacuum pump is running a lot, this should stop it. Don't try to repair it, just keep it to the right a bit.

Have gotten a PM from 3 other members with the same problem as we had. Cured all.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: vacuum pump cut off switch

Reply #9 –
Quote from: lovetogo –
Talking about vacuum...Back in jan, on my maiden voyage. I had no dash heat and the hvac was stuck on deforest could this be my issue . are is their a hot water shut off some where. one good thing is that when i move the switch to ac. the ac compressor engages...and thats a good sign  ^.^d   

Yes, without vacuum, the default position for the dash HVAC is defrost.  So, yes, you need to diagnose the vacuum system.

Not aware of a factory shut-off valve for the dash heater core-- yes for motor-aid water heater.  BUT, one could certainly have been added by a previous owner.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: vacuum pump cut off switch

Reply #10 –
In our 89 GV, as Gary Boulard stated, open the door under the sink, reach around near the floor towards the front of the coach. There is a hole cut in the cabinet interior wall. Reach thru the hole and you will find a valve with a round fretwork knob on top. Open directs the water one way and closed the other way. Which way I don't remember because I wrote the direction info on a card and stapled it in the cabinet above the hole. Check with Gary, as he knows.
Brett, I tried putting my thumb over the pump outlet and not much vacuum. Tried blocking the vacuum lines at different accessible points and the pump never shut off so I added a toggle switch. Now I can turn it on or off when I want. Not good as the doors close when the vacuum is gone. Spring return apparently.
Nitehawk,  Demolition Lady, & our NEW master, Zippy the speeding BB cat.
1989 Grand Villa 36' ORED
Oshkosh chassis, 8.2 DD V8
2006 Saturn Vue AWD

Re: vacuum pump cut off switch

Reply #11 –
Valve open coolant goes thru motoraid in the water heater, closed goes thru dash heater core.
Gary B