I have got to replace the vacuum pump that is used to open and close the defroster and dash air doors.

Rusty found this one for me
This one

Has anybody else had to replace this pump and what did you use before I order this one.

Nick

Nick, That is a very common pump I see used for cruise control on some of the older imports I work on. I may be able to come up with a used one if you want to go that way.

Neil.

Thanks Neil, anything that will save a dollar. Let me know

Thanks,
Nick

HI Nick, I also have a used one you may have. I had them on my Breakaway but after about one year, they both failed. I had two or three spares. Most of those pumps are not continuous duty and are turned on and off by either a vacuum switch or controller. I had a vacuum switch but it was set to high and would run continuously if I was over 3000 feet altitude. I have since replaced the pumps now with one to run the HVAC (electronic cruise no need back there now)and changed the vacuum switch to a lower level so that the new pump will not run at higher altitudes.

I may have the switch specs and maybe have a switch around also.

I am also working at replacing the vacuum venturi by a Volvo vacuum pump similar to the one you are looking at. I am currently in contact with a representative of DesignFlex for a switch (they are giving a free sample !) The selected switch is adjustable between 6 to 25 in. Hg. ( hysteresis one third of set point) ; should get it next week.
On the pump, there are 3 wires (one of the wire seems to control an relay in the pump ?) Would anyone have an idea how to wire it. I probably know just enough to get into trouble !!!
Michel
92 Breakaway 30’
5.9 Cummins Banks PowerPack
Allison 4 AT542
Spartan chassis

I replaced my venturi pump with one similar to that in your picture. Got it from Specific Climate Systems http://bg.motorhomemagazine.co...ate.cfm?s_booth=2234
and paid about the same. Has worked fine.

I just bought the Ford air driven one from Spartan a couple of years ago. The one in back was missing when we bought the Barth. It only needs to run the cruise in the back. Up front the original is still working fine after 17 years.

Here is a picture of the Volvo vacuum pump and connections to it.


If the port that has a hose running back to the main body (unloader valve) is blocked off, then no need to hook up the unloader valve to +12V. The exhaust port may be left open and leave the hose going back to the main body connected also.

I also tried to get the Ford air operated unit from Spartan recently and was told it is NLA, I also tried a search Nationwide and was told the same thing, it is NLA.
HTH

This is a couple of pictures of the old vacuum pump.



The pump is made by Gast Mfg. Corp. I am going to try to replace it with the pump pictured by ED.

Nick

Nick, before you replace it, I'd try brute-force separation of the motor from the pump. When I had it apart (with the motor case removed), the pump would turn freely. When reassembled, the bind returned.

I suspect the coupling between the motor and pump crank is frozen. The diaphragm and reed valve looked to be in excellent condition, and the crank and conrod bearings seeemed OK, too.

"Originally posted by Nick Cagle:
Thanks Neil, anything that will save a dollar.

Thanks,
Nick"

Nick, E-mail your address and I will send you one if you still want it. It may not be the best chioce for this application though.

Neil.

I don't know how much volume we need but since the ford unit is gone maybe the following

http://www.vacmotion.com/Ventu...uum%20generators.htm

at least interesting.

You can also get some cheap venturi generators that are used of evacuating ac systems.

Called the above company and you can order them on line for less the $50. The guy didn't know much about the RV usage, said they just sold one a couple of weeks ago for this application. He recommended the inline single stage. This is the picture in the middle.

The problem with all these is that the venturi generator needs a regulator and cut off, otherwise it will deplete the air system very FAST! On my old units that is what failed, The venturi generator was OK and I sent them (venturi) off to another Barth owner.

I am not in favor of continually exercising the air system just to get some vacuum to operate the HVAC. Vacuum operated cruise control is the worst! Everytime the air pump operates, condensation is added to the dryer and shortens the life of the system components.

Finally got around to installing the Volvo vacuum pump and cut-off switch that Ed send me. The pump does generate enough vacuum to operate the doors.

The system must have enough leaks that the cut-off switch never completely cuts off the pump. I am wondering about installing a manual switch in the dash to cut the pump off when I'm not trying to operate the doors.

Below I have attached a couple of pictures so you can compare the difference in the original pump and the Volvo pump. I have also located a source for the original pump if I have to replace the Volvo unit because of size and power.

Model MOA-V111-JH $274.00
James Watson & Co.
29 Doran Ave
Marietta, GA 30060
770-422-1154


As you can see there is a considerable difference in the two pumps.



Nick