Today was another day of variety.  After our usual coffee and granola I drove over to the Quartzsite Market Place dry-camping area where the Western GM Bus Rally was still taking place.  I met with Larry and Carol Hall and spent over an hour photographing their GM PD4106 bus conversion.  It was very nicely done and they had straightened it up so that there wasn’t anything extraneous lying around inside.  Larry was also kind enough to move the bus several times to allow me to get an angle of view with a good background and lighting.  An article on this bus conversion will appear in a future issue of Bus Conversion Magazine.

Larry & Carol Hall’s GM PD4106 bus conversion at the Quarzsite Market Place.

When I was done with the photo shoot I returned to our coach to transfer the image files from my camera to my computer, organize them, and back up them up to our NAS device.  For lunch we had tofu hotdogs wrapped in tortillas with mustard, onions, and pickle relish.  I then talked to Butch briefly about the TPMS vendor Linda and I spoke to yesterday in the “Big Tent” and discovered that we had talked to different vendors about different products.  I also let him know that I was going to work on our air-conditioners.

The three house air-conditioners (A-C) in are bus are Cruise-air split units and are initially controlled by three 12 VDC switches on the lower right dashboard.  Those switches get their power from a single 2 Amp fuse in the low voltage distribution panel.  The A-C’s did not work the last time I tried to use them (at Martin Diesel) and I found that this fuse was blown (open) so that was the place to start.

I pulled the old 2 A blade style fuse out of the distribution block and checked for voltage on the supply side and no voltage on the load side, and that is what I found.  I then checked for resistance from the load side of the fuse holder to ground with all three switches off and with each switch turned on, one at a time.  The resistance was infinite (open circuit) with all three switches off (as expected), ~45 Ohms for A-C switches 1 and 3, and ~450 ohms for A-C switch number 2.  All three switches control relays in the DS rear corner of the bus that switch on AC power from the breakers in the AC distribution panel.  Two of the switches also control the solenoid air-valve that controls the air-powered shutters for the two condenser units in the front spare tire bay.  So it was reasonable that one of the switches might show a different resistance from the other two when closed, but at this point I did not know if any of these measured values were correct or even reasonable.

I borrowed a 6 Amp auto-resettable circuit breaker from Butch and inserted it into the fuse slot.  Our testing revealed that switches 1 and 3 caused the breaker to trip but switch 2 did not, and it did not matter whether the 120 VAC power for each unit was turned on at the circuit breaker.  The evaporator units and control panels in the house, however, did not come on unless the 120 VAC power was on along with the 12 VDC corresponding dashboard switch.  That confirmed that the dashboard switches are controlling AC power relays.  I knew from previous work that those relays were in the driver’s side rear corner of the bus/bedroom but our testing indicated that they were probably not the problem.

The common element for switches 1 and 3 was the MAC solenoid air valve on the air panel in the bay under the driver’s seat.  This valve controls air-powered shutters at the front of the spare tire bay where the living room and kitchen A-C condenser/compressor units are installed.  The shutters are held closed by air pressure and held open by a spring in the absence of air pressure.  I keep the air supply valved off when we are parked to minimize air leaks and reduce how often the auxiliary air-compressor runs, but when compressed air is applied to the valve, which is ‘normally open’ when the front A-C units are off, the air pressure closes the shutters.  If either front-located A-C unit is enabled at the dashboard the MAC valve closes off the air supply and vents the pressure on the shutter actuator, allowing the spring to pull them open.

I disconnected the wires from the solenoid and confirmed which wire was the +12 VDC supply to the terminal strip.  I checked the resistance of the solenoid coil and it appeared to be shorted, so I left it disconnected.  We rechecked the A-C units and the two located in the front bay would still not turn on.  Butch figured that there was probably a limit switch on the shutters to prevent power from being applied to those two A-C’s unless the shutters were open.  I loosened the fitting at the valve to relieve the pressure and the shutters opened up.

With the shutters open and the solenoid disconnected we finally got all three A-C’s working, so we have fixed the problem for now but not permanently as the system not does function as designed.  As a side note, it appears the three control switches are incorrectly wired.  Switch 1 is the front A-C, switch 2 is the center unit, and switch 3 is the bedroom.  Switches 1 and 3 are wired to control the shutters for the spare tire bay but the compressor/condenser units for the front and middle A-C’s (1 & 2) are located there.  My guess is that this has been miswired since the coach was built.  The wiring needs to be corrected and I added it to my project list.  Until then, the “fix” is to just make sure all three switches are ‘ON’ anytime we are going to use any of the air-conditioners, ensuring that the shutters are open and the units will operate.

Camp Lieberville in Quartzsite, AZ (our coach is not shown).

We left around 3:40 PM and drove over to the Quartzsite Yacht Club for the 4 PM RVillage get-together that founder/CEO Curtis Coleman had scheduled.  Curtis was already there with Patti (the Village Tart) as were Chris Dunphy and Cherie Ve Ard (Technomadia), Jim and Chris Guld (Geeks On Tour), and our friends Butch and Fonda Williams (MCI MC-9 NJT and W9MCI and K9MCI respectively).  Lots of other folks showed up including Forrest and Mary Clark, the first two RVillage Ambassadors.

We left a little after 6 PM and drove out to the WINs area on Plomosa Road to deliver a birthday card to Mara.  Her sister and brother-in-law were there but left shortly after we arrived so we stayed until after 8 PM visiting with Mara.  When we got back to our coach Linda heated up the leftover root vegetables for dinner.  She read while I updated my BCM article status spreadsheet, checked e-mail and RVillage, and worked on this blog post.