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Topic: Vacuum pump operation?  (Read 587 times) previous topic - next topic

Vacuum pump operation?

With either just the key to the on position (not running), or even with the main engine running, I hear a pump running up front for just a few seconds -- and than maybe 10 seconds later it kicks in again.

I found it coming from this pump. Is that normal, to short cycle like this?
I'm assuming it is to supply vacuum for the dash Heat-A/C vent flaps?

 
Michael
1995 U300SE CAT 3176B Build # 4612 ("Marvin")

Re: Vacuum pump operation?

Reply #1 –
Michael, That is the vacuum pump that supplies vacuum to the AC and Heater dash controls.  If it is cycling often there is probably a leak in a vacuum hose.  Close off the outlet and see if it still cycles, it should not.  Then go looking for aged cracked lines to heater AC controls.
Gary B

Re: Vacuum pump operation?

Reply #2 –
Thanks, Gary. Will do.
Michael
1995 U300SE CAT 3176B Build # 4612 ("Marvin")

Re: Vacuum pump operation?

Reply #3 –
Quote from: geomm –
With either just the key to the on position (not running), or even with the main engine running, I hear a pump running up front for just a few seconds -- and than maybe 10 seconds later it kicks in again.

I found it coming from this pump. Is that normal, to short cycle like this?
I'm assuming it is to supply vacuum for the dash Heat-A/C vent flaps?

 

Our vacuum pump started to cycle on and off. So here is what I came up with.

Yes, it supplies vacuum for vent flaps and the Ford heater/air controls. Your problem is probably in the Ford unit. After spending about an hour troubleshooting, I found the problem in the slider for the temperature. Just move the slider about a quarter inch or so to the right and it should stop the cycling. I posted the cure and found there were a couple of other members with the same symptoms. Heat & Air Vacuum Pump

Cure: just keep the slider slightly to the right or use a tiny piece of plastic or what ever to block the last bit of travel. Might superglue it in place. Let us know if this does the trick.

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

Re: Vacuum pump operation?

Reply #4 –
Thanks, Pierce!

This forum Rocks!
Michael
1995 U300SE CAT 3176B Build # 4612 ("Marvin")