Dash A/C Vent Selector Buttons Inoperative following front end work

engineer bill · August 16, 2014, 09:49 AM

Last week I had my 1989 Winnebago Warrior 22EC P30 7.4L 454 Chevy Chassis serviced at great front end shop in Richmond CA called J & O Commercial Tires. They have the racks, alignment gear and experience to solve a lot of Ride/Handling/Steering problems on Winnebagos. (More on this in a more appropriate place if I can find it.)

When I drove into the shop, my dash mounted A/C worked pretty well, in the sense that the air flow came out of the correct dash, defrost and heater ducts per the control buttons. (The amount of cold air supplied in any mode is a whole different issue.) The shop added new tires, a LH bell-crank and an alignment. Now, the A/C controls don't divert the direction of air flow so all the flow comes out of the windshield defrost and heater ducts. None of the buttons changes the direction of the air flow. BTW, the A/C compressor is switching on/off when the control button for "Max Air" or "Air" is selected. I understand that most A/C units of this vintage use manifold vacuum to open and close air "valves" to divert/direct the flow to the correct place and that defrost position is probably the default when vacuum is not connected. I suspect that the A/C control unit "lost" it's vacuum supply. Other than this symptom, the RV seems to be running normally.

Without completely checking out all of the dozens of vacuum connections, does anyone have a guess which line might have been dislodged during this service that might cause this failure?
Does anyone know where I can find a complete vacuum hose diagram for this engine? Another shop had recently recharged my A/C system, twice, but the "cold" is disappointing.
Any thoughts on improving A/C performance?

Thanks everyone.

p.s. Otherwise very happy with the new tires, steering improvement and alignment.

Rickf1985 · August 16, 2014, 10:29 AM

There is one vacuum line that comes down rom inside the dash to a vacuum canister under the hood. Mine has two, one is for cruise control and the other is heater controls. They are a round ball looking canister made of plastic and should have two vacuum lines on it. One from the engine supplying vacuum to the canister and the other going to the heater controls. I would guess that in the process of working under the cramped quarters of the hood one of those lines may have gotten pulled off. On my Winnebago they are on the drivers side under the hood up high.

DaveVA78Chieftain · August 16, 2014, 04:28 PM

Because of the custom body design, the dash heating and A/C systems are built by Winnebago for Class A rigs. As such those systems are not covered in the GM P30 Chassis manuals. Even so, I suspect the Winnebago version is similar in concept to the GM van version described in the P30 Service manual. So, to make sense of how the system is put together, I would use that as a baseline to start from.

Dave

engineer bill · August 19, 2014, 09:53 AM

Thanks Guys! Here is the booboo. Disconnected vacuum line on HVAC vacuum can. (Ref. attached photo.) I guess to the shop mechanic it might "feel" like it was connected. I didn't see this until I looked at the pictures-it was not visible from my vantage point. I connected the hose properly and now the HVAC duct switching works normally again.

circleD · August 19, 2014, 10:34 AM

good eye bill.

engineer bill · August 19, 2014, 11:21 AM

I found my vacuum diagram on the side of the air cleaner under 25 years worth of grime. Once I cleaned it up with a little denatured alcohol it was quite readable. Here's a picture. Now I just need to lookup all of the device codes and I'll understand it.

cncsparky · August 19, 2014, 12:56 PM

After getting my coach about 2 years ago, I went through the vacuum hose mess and traced each one out just for the heck of it W% . Found most of the lines were badly cracked and needed replacement.

circleD · August 19, 2014, 09:46 PM

I traced mine also sparky and bought more than enough tubing to replace it all. So I cut and replaced it all piece by piece taking my time and feeling like I'm the man. Then when I put my Edelbrock on I took off 3/4 of them 4 months later :)rotflmao. I didn't know I was going to get a new carb until later. Oh the irony. On the plus side Bill, I learned ALOT about the vac lines

engineer bill · August 20, 2014, 06:24 PM

re. Vacuum Lines

I expect to be living in California for the foreseable future so I need to be able to pass the regular smog test. A part of the test is a verification that there have been no modifications to the smog system (which is basically the carb, vacuum hoses and assorted gadgets). I lived in LA in the late 60's when you couldn't see six blocks due to the orange haze from smog in the air so I think it's important to do my part.

I wanted to add to something I said earlier. The amount and temperature of "cold" air is not very impressive. I was told that the system had been serviced when I had it in the shop a few months ago. And, I understand that the original cooling gas (R12 freon) is no longer available but I'm not really up to date on the current state of the art of fixing these older units. Anyone care to enlighten me?

DonD · August 20, 2014, 07:32 PM

Bill, I used a drop in R 12 replacement with excellent results. I shopped around online to get the best price. The shipping price is the major difference. I use the cab AC a lot!

Rickf1985 · August 20, 2014, 08:42 PM

My 89 has 134. I think this was a complete changeover because they are not adapter fittings. Years ago when R134 was first starting to be used it was though that you had to completely purge everything from your old system AND replace all of the hoses. This has been found to not be true but thanks to the wonder of the internet their are still those that say it has to be done.
To convert to R134 which is the only RIGHT way to do it you have to get adapter fittings that install over the fittings that are on there now. If your compressor is bad now this is a perfect time to switch, you can get the hose blocks with the 134 fittings already on them plus start out with a new compressor designed for 134. You will have to have the system drained by a AC shop and unless you are doing the work yourself this will be the same shop doing the install. You will need to replace the receiver/drier and the expansion valve. These would have to be replaced anyway if the compressor was bad to cover the warranty. Also good practice. The oil used in the 134 system is PAG oil which is different from the Ester oil used in the R12 system. The more components you have to replace the better because the components do not come with oil and there is a chart that tells you haw much oil to add for each component. If you are going to use you old compressor you will have to remove it and drain any oil that is in it and replace with PAG oil. All of the conversions I have done worked well, 90% were as cold as the R12 and the remainder were real close. None were what I would call unacceptable. You will need a set of AC gauges to refill the system so you can watch both the low and high pressures to be sure when the right amount of refrigerant is in.