vacuum pump cycles frequently

[Kim Petersen]

2004 Horizon Itasca diesel pusher. The vacuum pump located above the drivers side front wheel inside the generator compartment cycles on and off every few seconds. I suspect a vacuum leak. what is the purpose of this pump, and also the wire from the ignition is constant hot. any advice or knowledge would be immensely helpful. Thanks in Advance.

[rgvtexan]

The pump is for the heat/AC system. It operates the hot water valve and the servos for dampers.

The wire should be hot with the key in run or accessory.

You have a vacuum leak. Trace out the small colored tubing.

[cbeierl]

Here are a couple of earlier threads with pics, etc. that might help: Vacuum Pump Failure and vacuum line leak anyone?

[Jim_HiTek]

On my '02, that is the pump for the comfort controls as mentioned. Mine runs and stops within 30 seconds of turning on the key.

I found a short split rubber hose on the upper left of the firewall on my '02, on a friends '04 Journey. You can see the green vacuum tube going to that round black water valve, that's where I found the short rubber piece that directly attached to the back of that was split. Couldn't see it from the front so check yours too because I've seen several of them split there:

[NeilV]

Those hard plastic vacuum lines are extruded and tend to become perforated along the seam that runs the length of them often due to UV light exposure, Also be sure to check for any accumulator tanks that may be found mounted to the frame rails or behind the front frame member as the rubber adapters that connect the vacuum tanks to the plastic lines tend to rot out too. You can use a length of rubber hose of the appropriate diameter cut into 1 or so inch lengths to replace those adapters or to use as splices when replacing damaged sections of the plastic tubing. They may have it listed as emissions tubing at your local auto parts store and its often only available locally in black.