Problem with vacuum pump not turning off

[jhanan]

So there is this small vacuum pump mounted on the firewall. It wont turn off. I check the line and it is ok. If I remove it and plug the input with my finger, it will turn off. I also check the other side of the small reservoir and if I plug it up it also stops. There is transition to small line about 1/8 in and goes back behind the firewall. Anyone know what this vacuum is service for?]

2002 Horizon, FL XC chassis

Thanks, Jeff

[cbeierl]

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

[Pelledan]

That pump provides the vacuum to operate the A/C, Heat, and vent position controls for the dash controled environmental systems.

[dc8cappie]

I have a leak when my AC/Heater control is in the OFF position. I have to leave the system on in any position except off to get the pump to shut off. In other words, I don't turn the system to off.

I have a new vacuum manifold that I will install some day as I also found the lines starting to crumble, so, its time.

[jhanan]

Originally Posted by Pelledan

That pump provides the vacuum to operate the A/C, Heat, and vent position controls for the dash controled environmental systems.

Interesting. The dash controls are working fine. I can go from heat to ac to vent, so there must be a leak on that line. Will have to pull off the dash hood to check it out.

[jhanan]

Originally Posted by dc8cappie

I have a leak when my AC/Heater control is in the OFF position. I have to leave the system on in any position except off to get the pump to shut off. In other words, I don't turn the system to off.

I have a new vacuum manifold that I will install some day as I also found the lines starting to crumble, so, its time.

Will have to play around with the setting to see if I can get it too shut off. I must say that is a pretty good vac pump because is has been running for hours and still running.

[Pelledan]

The actual control knob (Heat;Vent; A/C; etc) is connected to a vacuum manifold with about 5 different vacuum lines connected to it. Each of those lines needs to be vacuum checked that they are leak free. In some cases, one position of the control knob (and one of those vacuum lines) will work perfectly and the pump will shut off, while another position may have the pump running constantly because the vacuum line connected to that position has a vacuum leak. If your pump is running constantly, the first thing to check is the small green line that connects the pump to the heater control. That line is notorious for cracking at the heater control. The connection there has the line transitioning to something that looks like a mini spark plug boot where it connects to the heater control. Look there first. If that's fine, then your problem is one (or more) of the lines connected to that manifold.

Dan

[jhanan]

Originally Posted by Pelledan

The actual control knob (Heat;Vent; A/C; etc) is connected to a vacuum manifold with about 5 different vacuum lines connected to it. Each of those lines needs to be vacuum checked that they are leak free. In some cases, one position of the control knob (and one of those vacuum lines) will work perfectly and the pump will shut off, while another position may have the pump running constantly because the vacuum line connected to that position has a vacuum leak. If your pump is running constantly, the first thing to check is the small green line that connects the pump to the heater control. That line is notorious for cracking at the heater control. The connection there has the line transitioning to something that looks like a mini spark plug boot where it connects to the heater control. Look there first. If that's fine, then your problem is one (or more) of the lines connected to that manifold.

Dan

OK, that's it. Looks like off, vent, and heat are leaking, but the AC and Def is not leaking- pump turns off. Thanks