Dash a/c airflow

CJ7ole · 08-14-2013, 08:48 AM

I seem to get a good airflow from my dash a/c only when the engine is not loaded, ie: idling or going downhill. Even on the flat at 60 mph I get just a trickle of air from the dash vents, regardless of the fan speed. As soon as I crest a hill and start down, I get a nice rush of cool air. Obviously a vacuum issue. While on the road in Sioux Falls DS took it into a truck shop that works on RV's, he agreed and replaced some vacuum hoses and fittings that were brittle. At first I imagined that it was working better. Not so. Does the 2002 F53 rely on engine vacuum or is there a vacuum pump? Any ideas? Thanks in advance.

Skip426 · 08-14-2013, 10:00 AM

The majority of gas engine coaches rely on engine vacuum, for dash A/C controls.
Your coach should have a check valve & reservoir ( soft ball sized plastic ) to maintain vacuum when the engine is loaded.
You may have a vacuum leak in the dash that leaks the vacuum, and returns the system to default ( usually defrost , so all the air goes onto the windshield) or the reservoir could be too small.
I had to add a second reservoir to my last two tow vehicles, for the condition you describe.
Unfortunately the hand held vacuum pump required to test your system for leaks is fairly expensive, but may be available for rent at a local auto parts store.

bruceisla · 08-14-2013, 10:11 AM

You can try an ear syringe instead of vacuum tester. Squeeze the ball, connect the hose, release the ball, pinch the hose to trap the vacuum, unattach and re-squeeze ball and then reattach hose (while pinched), unpinch and ball should stay collapsed. You usually need the 2 squeezes to get the air out of the system for a valid leak test.

http://www.walgreens.com/store/c/wal...031727-product

Brockx · 08-14-2013, 10:23 AM

A couple of people have found "loose" connections behind the dash at the control area. Regardless; you have a leak just need to find it.

bobpie · 08-14-2013, 03:42 PM

I have found a junction CAN behind the passenger side front tire/bumper with some vacuum hoses gooing to it and soft putty like sealer around the hose connections. Touch up the putty with the engine running to stop the vacuum leaks. If you have good ears you can hear it hissing at the connections. Now I have vacuum to all the settings on the dash AC/Heat selector

rdoghse · 08-16-2013, 08:42 AM

We have the same problem with our '01 Adventurer, F53 chassis. We use the A/C setting vs. the Max A/C, on the selector knob.

Skip426 · 08-17-2013, 09:40 AM

Quote:

Originally Posted by rdoghse

We have the same problem with our '01 Adventurer, F53 chassis. We use the A/C setting vs. the Max A/C, on the selector knob.

If one mode of your A/C has the problem, and others do not , I would suspect that , in your case, the Max A/C, recirculating air door vacuum actuator; or vacuum supply line to it ; is leaking.
Also possible that your system uses a vacuum , water valve, and there could be a leak there.
Max A/C, does two things , shuts down water flow through the heater core, and moves the recirculating air door, so your system doesn't take outside hot air , it re-cools the inside air.

Izzyblueye · 08-18-2013, 09:39 AM

This has been a problem for a long time. Ford I believe put out a tech bulletin on a fix, check with Ford RV cust Sv or a good dealer, if there is such a thing.

BFlinn181 · 08-18-2013, 10:52 AM

Quote:

Originally Posted by Skip426

Unfortunately the hand held vacuum pump required to test your system for leaks is fairly expensive, but may be available for rent at a local auto parts store.

They usually are expensive, but here's one for about $22. Brake Bleeder and Vacuum Pump Kit

An electric vacuum pump could be added also, although I'd first try to find the leak or faulty check valve.
APDTY 015325 Vacuum Pump - Electric 12 Volt Supplemental For HVAC; Brake; Cruise on eBay!

toneumanns · 08-18-2013, 10:55 AM

Had the same problem. Rodents had chewed into the vacuum line.

bobpie · 08-18-2013, 07:31 PM

You need wild cats in the back yard like me and there are no more rodents.

Hikerdogs · 08-19-2013, 10:02 AM

We had a situation similar to bobpie on our 2001 Adventurer. I checked all the hoses and the both canisters under the hood with a vacuum pump. I never found a leak and even added another canister in line with the round one. I still had the problem of losing vacuum on long uphill pulls. I finally removed the lines to the canister by the bumper and smeared some silicone grease on the connectors sticking out of the canister. After reattaching the plug there was never another leak. Apparently the vibration of movement was causing a slight leak at the connection. Never enough to bother except on very long uphill pulls the exhausted all the vacuum in the other canisters