Community Forums

Jimbabs · 07-03-2012, 12:15 PM

My dash AC cools ok, but it's stuck on defrost...none of the air comes out of out the front vents on the dash. Doesn't matter what position the selector is in. I have a 2005 Diplomat....anyone know what's going on??
Thanks for your help.
Jim

RustyJC · 07-03-2012, 12:47 PM

Defrost is the "fail-safe" mode that the system goes into when there's no vacuum available to move the damper doors. The most typical cause is a vacuum leak due to a cracked or disconnected hose, a cracked vacuum reservoir, etc.

Rusty

chief02 · 07-03-2012, 12:54 PM

what Rusty said

Tom-NC · 07-03-2012, 01:31 PM

Hi,
It sounds like you have a vacuum leak or a vacuum hose that came off. I would check around the master cylinder area for a disconnected vacuum line. It could also be at the engine as when hoses get to hot they become brittle and break. It is definitely a vacuum problem.

AtlantaRick · 07-03-2012, 01:40 PM

I have the same exact issue so I hope you keep us up to date on what you find out. I will do the same.

rex · 07-03-2012, 02:19 PM

There is a resistor pack on the unit outside in the generator compartment. That is normally what caused the air to only come through the defrost vents. It has a thermal fuse that blows and causes the problem. Normally it is a Ford part buy you should be able to find it at NAPA or other auto parts stores.

There are two different resistor packs that I know of as shown in the attached pictures. The first two pictures are of the same type, just different views.

Your pack may have a cover over it.

RickO · 07-03-2012, 03:58 PM

Hi and welcome to the forum.

I have merged the two threads you started on this topic since we don't allow duplicate posts.

Best of luck.

Rick

Rockcrawler · 07-03-2012, 04:17 PM

The pic Rex showed is a fan speed unit. If the fan is not running at all, this could be an problem. If your fan IS running...look for a vacuum leak.

ahicks · 07-03-2012, 06:24 PM

I agree, lack of vacuum - but if you don't hear an electric motor humming full time, or one cycling on and off constantly, there may be nothing wrong with the vacuum lines, it could easily be the electric pump has quit. There is no engine vacuum available on a diesel. Blown fuse, worn out, whatever. Mine's mounted on the firewall, under the hood.

Jimbabs · 07-16-2012, 08:47 PM

Thanks to the info I got from the posts, it was a vacuum problem...checked and there was no power to the vacuum pump (located under front hood next to small round vacuum ball)
and couldn't find the right fuse...called Monaco and found out that it's mini fuse #19. Put a new one in and the pump didn't work...it's a Ford product and we got a new one for $280. Easy install and now the problem is solved!

AtlantaRick · 07-17-2012, 05:43 AM

Jim - where is this mini fuse located?

Jimbabs · 07-17-2012, 08:36 AM

Rick...the fuse is in the large fuse panel...mine is in the front driver's side compartment.

AtlantaRick · 07-19-2012, 04:46 PM

Had the coach serviced today and they diagnosed my problem with the AC stuck on defrost as a bad vac pump. Hopefully I can find a part number when I take it off. It looks like it has been replaced before because the power wires have obviously been spliced. So who knows what mfg this one is.

AtlantaRick · 07-20-2012, 12:15 PM

The rectangular black box to the right of the round vacumm canister is what I was told was the vacuum pump for controlling the air vents. I disconnected the supply line at the bottom of it and high pressure air came out and it drained my air tanks. So, I am having doubts this is the vacuum pump. I hooked it back up and recharged my air tanks and then pulled the rubber hose off that leads to the round canister. There might be a vacuum but if there is - it is almost non existant. My quest to fix this thing continues but I am hoping somebody has some ideas or where I can look for the pump if this is not it... or do you think this box is bad. There are no numbers on it.
Rick