'91 SP36 overhead cab AC

[MsBianca]

Hello all, please forgive me as this will be one of many threads I/we end up starting in addressing minor issues with our newly acquired coach.

So after our pick up during a snow storm, by the time we started getting further west, it warmed up. When I tried the AC unit that is overhead, a few issues came up:

1- the driver's side blower was about as strong as an asthmatic blowing through a straw (Jeremey Clarkson quote). The passenger side blows just fine it seems.

2- Neither was very cold. I'm assuming this denotes the need for a recharge at a minimum.

3- The trip computer only starts counting distance if the driver's fan is turned on? Yeah, that one has me pretty stumped.

So these lead into my questions:

1- Is this just a regular automotive AC unit? That is, is there a compressor all the way in the back and lines run all the way up front? Or is this a "standalone" much like the other 2 "house" units?

2- I've completely overhauled AC systems before and even converted R12 to R134a. Are the principles the same and it's just a matter of determining where all the components are?

3- Is the driver's side blower motor just getting ready to die, or is there something else that would prevent it from blowing very hard?

4- Any ideas on the trip computer deal?

Thank you for being patient with us as we learn all the systems and get the coach back to perfect.

[gcyeaw]

AC unit is like automotive units. Compressor on the motor in the rear. Very few work, and usually after many dollars only work for a season or so. Condenser is on the roof in front (not certain about SP), evaporator is in overhead with blowers.

[MsBianca]

Got it. Thanks! I'm guessing the issues stem from the distance the refrigerant (and frankly the volume I'd think) needs to travel from the compressor up to the cab and if there are leaks, I suspect finding them (or replacing the lines) would REALLY suck.

I'm going to have a go at it and see what I can find. I think the compressor is a York (I did a bit more research after starting the thread) which are very stout units easily and relatively cheaply serviced/replaced.

Is it a total bear to remove the overhead console to have a look see?

[mose]

I assume that your PT is similar to my '91 WB. If so.....

The AC evaporator is on the far right in the overhead compartment. Then there are ducts that go over to the driver's side. These were badly crushed by years of settling, rewiring, etc., so it could just be the ducting and not the fan. This pic shows the upper ducts; the worst ones were down by the vent outlets.

My chassis AC doesn't work either. So far I've traced it to a bad temp cycling thermostat, that never calls for 'cool'. It's a probe that goes into the evaporator and then a slide switch at the overhead AC controls. Also attached is a nice drawing of the electrical (complements of John Wyatt, not me). Those relays are in the overhead compartment as well. I think my electrical also has a low temp cutout switch just before the compressor.

[bubblerboy64]

From a cost to benefit I doubt it's "worth" fixing the engine (dash) AC.

[gcyeaw]

I just fire up the gennie and run the roof airs like most others. The long old hoses leak and converting to R34 only makes it worse. If you are patient, able to reach into small places, and understand the system it can be fixed. But even then it only cools the dash area, not the whole coach.

[Randy Dupree]

On the SP36,the lines from back to front are copper,with only a short rubber line on each end.
The WB coachs are the same way.
I have no idea when this started,what year or models,but i know the 89SP and the 93WB both have copper.

[MsBianca]

All wonderful info! And if it is only rubber at both business ends like Randy said, finding a leak is easy peasy as would be swapping out the O rings to R134a compatible ones. Even getting the hoses made is easy and relatively cheap.

The only thing that would be suspect would be that the condenser is much less efficient as it was probably designed for R12 and may not allow for cooling cooling as strong once converted to R134a. But even that is something that can be addressed. In an old BMW I had (a '91 ironically) there were condensers that could be retrofitted that were the same size and port location.

And mose, that first picture was HUGE! It will be much easier to get in there than I initially thought. Also, knowing the wiring a bit is a big help.

Again, the purpose of the exercise is just to cool off the cab. I suspect for this first season, we'll be using the generator and the house units as the kids and dogs will be with us, so they need to stay cool as well. Also, running the generator for the drive home didn't prove to dramatically impact economy, so I'm not worried about that part.

The best part again of getting an older coach is the ease of fixing stuff- and since it's so big, I don't necessarily have to fold myself up like origami to get to things.

[mose]

Originally Posted by MsBianca

And mose, that first picture was HUGE! It will be much easier to get in there than I initially thought. Also, knowing the wiring a bit is a big help.

I've been in and out of there many times now. Not sure if the SP and WB are identical up front. And there are different cabinet options as well. Mine has white vinyl flippers on either side of the TV. Others have wood doors instead. However in both cases, there's carpeted plywood panels inside that can be removed relatively easily. Screws in each corner that can be found with a magnet. There are also four big bolts that can be removed and the ENTIRE panel hinges down for access to the back of the upper gauge panel, speakers, ducts, etc. Let me know when you get in there.

Originally Posted by MsBianca

Also, running the generator for the drive home didn't prove to dramatically impact economy, so I'm not worried about that part.

We just acquired ours last summer. Maiden voyage was from Vegas to Oregon. I didn't want to run the generator or AC as I knew little about the condition or maintenance. And our dash AC didn't work. It was 108F outside when we left Vegas, and a dash mount inside temp gauge was reading 126F. My only relief was a cooler full of ice and a wet T-shirt on my head.

[Camper Dave]

The dash AC may still work. You appear to be a gear head so I may be stating the obvious, but check the following before you spend $$$$, as John stated it may not be cost effective.

1) I would ensure the compressor clutch engages. Turn on both right and left blowers...unfortunately you have to walk to the back and check.

2) Make sure you have power at the compressor, mine needed a re crimp.

3) Then make sure both condenser fans are turning.

4) If all the above are in order I would puts some refrigerant in the line and hope for the best. My FC took one large can to get cool and I could still put another can in to get the required amount in the system. If your line is running from the back, your guess is as good as mine on how many cans you will need. Gardner is correct on cooling of the front only. I was in Palm Springs last weekend in 95 degree weather, if you were sitting on the sofa you would not feel a thing. However, I turned it to medium after 15 minutes of being blasted by cool air in the drivers seat. I drove solo so it was nice to leave generator off.