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mdlearnest · 01-24-2017, 04:53 AM

I'm fighting a vacuum issue in my 2000 F53 HR Endeavor V10 gas MH. On long uphill grades, my A/C almost stops blowing out the dash and splits between the dash and defrost. I've already replaced the badly degraded rubber connection by the vacuum canister on the frame by the passenger front tire. That helped, but there's another issue. I would appreciate if someone could send me the vacuum diagram to this rig. I feel like there is a check valve somewhere in the system that I cant find causing the issue. Any help would be greatly appreciated. Thanks

twinboat · 01-24-2017, 05:40 AM

Besides a bad check valve, you may also have a slight leak in one of the vacuum diaphragms or the control.

While hill climbing there is little to no vacuum being created from the engine, but the AC control system should hold what it has.

A small, hand vacuum pump, will quietly pull down the system to listen for a leak.

I also recall hearing about some of the, juice can looking, vacuum tanks rusting thru.

Sent from my VS880 using iRV2 - RV Forum mobile app

subford · 01-24-2017, 05:41 AM

I would say it depends on the brand of AC system you have.
Below are the diagrams for the 2000 V10 vacuum source and the Evans AC system.
By the way the vacuum canister on the frame by the passenger front tire has nothing to do with the AC Vent system.

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mdlearnest · 01-24-2017, 06:00 AM

thanks for the diagram. I've read about the softball sized canister, but for the life of me I can't seem to be able to locate it. I'll get out there again this morning and start tracing lines again in hopes of finding it.

mdlearnest · 01-24-2017, 06:01 AM

Thanks for getting back to me. I bought a handheld vacuum pump just last night. I'll get out there this morning and pull a vacuum on the system and see if I can hear a hiss.

subford · 01-24-2017, 06:12 AM

You can also go to the link below and click on the type control you have for information on troubleshooting your system.
Evans Tempcon, Inc

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TeJay · 01-24-2017, 03:18 PM

Bill,

Again your are right on these issues. When I first read these type of problems there are always two forum members who will respond quickly and thoroughly. You and twinboat. You two can always be counted on for a prompt and thorough covering of an OP's concerns. Your posts are very accurate and you have a wealth of schematics and pictures to help posters.

I realize this is not my post but I still want to thank both of you for all of your valuable information and specific troubleshooting assistance.

hillman · 01-25-2017, 08:46 PM

My 04 Winnebago has two reservoirs one in front of driver and another by front wheel.Only bad line I found was blue line to reservoir by front wheel. It is an Evan tempcon system.

mdlearnest · 01-26-2017, 05:21 AM

Thanks for all the info guys. As it turns out, my MH only has 1 vacuum canister(the one by the front pass. tire) so i installed the round canister fwd of the firewall to no avail. The system still bled down. It makes me question the whole theory of a vacuum canister in the first place. During the process of elimination I discovered a bad EVAC canister purge valve that wouldn't hold a vacuum. It will be here Friday and I'll install it Sat. morning. I'm fairly confident that's the issue due to the fact that when i unplug that vacuum hose and plug it, the air vents work as they should, no bleed down at all. I'll update the post Sat. Thanks again for all your help, its really appreciated.

mdlearnest · 01-27-2017, 05:59 PM

I just replaced the EVAP canister purge valve thinking that was where my vacuum leak was. Apparently, that valve must stay open all the time 'cause my issues are still there. I'm stumped. When i unplug the vacuum line at the canister purge valve (and plug it) my air vents work as they should. As soon as I plug that line back up, my air vents redirect to the defrost on up hill pulls. I'm running out of things to check. For starters, I thought that a vacuum canister was supposed to hold a vacuum on one side the vacuum was lost on the other side. If that's the case, i have 2 bad canisters (one of which is brand new). Again, if i unplug the vacuum line that goes to the purge valve and cap it, the system will hold a vacuum for 2 hours. I'm totally open to any ideas at this point.

twinboat · 01-27-2017, 08:24 PM

I looked at the diagrams and don't see a check valve.

If your heat system will hold vacuum, I would think a check valve would be needed just before the vacuum chamber, so The vacuum isn't lost, back thru the lines, to the EVAP system.

subford · 01-28-2017, 06:02 AM

You might read TSB 02-07-02, attached.

mdlearnest · 01-28-2017, 11:01 AM

As it turns out, I installed a $5 check valve between the OEM vacuum canister and the additional vacuum canister I purchased from autozone and the issue went away. Bill, I imagine the problem was actually a bad OEM canister like the TSB you mentioned. I'd like to thank all who offered suggestions. These forums are great!