The overnight low temperature was forecast to dip into the upper 30’s last night and only rise to 55 by 10 AM, finally making it to 64 by noon and eventually reaching 71 before dropping back to the mid 60’s by 6 PM.  A sunny day was in store with little-to-no wind—a perfect afternoon for working on the bus—so I called John and he agreed that he and Marian would arrive around noon to help with bus projects.  The forecast held true and the Hagan’s arrived right on time.  We discussed bus projects over lunch and decided to go after the cargo bay lights.

I had pulled out my various manuals, found the one with the wiring diagrams, and located the wiring diagram for the Interior Lighting, so John and I started there.  The diagram indicated that all of the bay lights were on 24 VDC circuits/breakers, and all of the cargo bays were powered from a single circuit/breaker.  The light for the auxiliary air compressor bay was on a separate/circuit breaker and the lights for the engine bay were on their own circuit/breaker.  The light in the aux air compressor bay did not work and none of the engine bay lights worked, but some of the cargo bay lights did work indicating that the circuit breaker was good and the wiring was OK at least up to some point.  The reason(s) the aux air compressor bay and engine bay lights didn’t work were unknown and need to be diagnosed.

The larger bays, which go all the way through the bus, have two light fixtures on each side.  The smaller bays (over the rear tires) typically have one light fixture.  The front aux air compressor bay also has one light fixture.  There are at least six light fixtures in the engine bay, none of which work, but that was not our focus for today.  These fixtures are all clearly indicated in the wiring diagram, along with the switches, connectors, and wire numbers.

All of the cargo bay fixtures are present but most of them are badly corroded.  Each fixture uses two 24 VDC bulbs wired in parallel.  Some had only one bulb and some had none.  We cleaned up one of the existing bulbs and determined that they are T635’s, a small bayonet mount 24 VDC incandescent bulb.

(Perhaps I should try to find an LED replacement for these?  Actually, I plan to replace all of the fixtures with LED’s, but that’s a project, and a story, for another day.  When I upgrade the fixtures to LED’s I will probably re-wire the front cargo bay so all of the lights come on when either door is opened.  This is our only real cargo bay; all of the other bays are full of installed systems.  It has a bi-directional slide, and it would be nice to have it fully illuminated.  I am also considering feeding the bay lighting circuits from the 24 VDC battery system through a fuse, relay, and diode so power would only be supplied when the chassis batteries are turned off, which is the normal situation when we are parked.)

According to the wiring diagram there are two branches to the cargo bay circuit, one for the driver side lights and one for the passenger side lights, except for the large front bay where all of the lights are powered from the driver side branch.  Each bay door has a micro switch that turns the lights by that door on/off when the door is opened/closed; at least that is what is supposed to happen.

I made a rough diagram of the bus bays with all of the fixtures and micro switches indicated.  I turned on the chassis batteries, opened all of the bays, and we started documenting what did and did not work.  We checked each fixture that did not come on to see if voltage was present.  If not, we checked the micro switch both for a supply voltage and for proper switch function.  We found one micro switch that was bad in the DS rear electrical bay.  We found another micro switch in the water bay that had one of the wires cut, but determined that there was 24 VDC present.  The only fixtures that were not receiving voltage were the PS front cargo bay and the aux air compressor bay.  We did not check the engine bay lighting circuit.  The engine bay is a messier place to work, and that will be a project for another time.

I had two new micro switches in my parts box so we replaced the bad one in the DS rear electrical bay.  The micro switch in the water bay did not have a spring/roller actuator.  We did not know if that was by design or if it had broken off but decided to remove it regardless as it was mounted in a location where it was difficult to work on.  We had to fashion a new wire for it that was long enough that we could splice it to the wire in the bay.  John was able to remove the switch at which point we could see that that the actuator spring/roller was broken off.  The switch tested OK, so we removed the actuator from the defective switch we had just replaced and put it on the existing switch.  We made our new wire, attached it to the switch, and spliced the other end to the existing wire in the bay.  We reattached the other wire to the switch and turned the chassis batteries on.  Voila, let there be light!  We cycled the switch to make sure the lights would go off and on.  They did, so we re-installed the switch.  We then gently lowered the bay door almost to closure but the lights did not turn off.

Examination of the switches on some of the other doors revealed that the spring/roller actuators had been “custom bent” to cause the door hinges to contact them “just right.”  We tried to bend the actuator without removing the switch, but spring steel by its very nature does not like to have its shape permanently changed and we risked breaking it.  Since these lights are powered by the chassis batteries there would not be any harm in just leaving them on as the chassis batteries are generally only on when we are going to start the engine.  I decided to look for a different solution (on another day) and removed the bulbs from the two fixtures for the time being.

24 VDC was not present at the micro switch for the front PS cargo bay and we could not trace the wiring as the converter (Royale Coach) had “buried” it behind a decorative carpeted ceiling.  We ran a jumper wire from one of the fixtures on the other side of the bay and determined that the switch was OK and so was the wiring from there to the light fixtures.  The solution in this case will be to disconnect the original supply wire from the switch and from the other side of the bay where it originates, cap them, and run a new wire; but that will be a project for another day.  My primary focus for today was diagnostics, with easy repairs where possible.

There was no 24 VDC present at the micro switch for the aux air compressor bay light so we used the jumper wire to supply power and determined that the switch, the  ground wire, and the fixture, including the bulbs, where OK.  This was the first power supply problem we had found.  The wires to the switch were numbered and the numbers corresponded to the wiring diagram.  We eventually found the other end of the supply wire, and the circuit breaker where it was attached, in the DS front electrical bay.  The breaker was OK and supplying 24 VDC to the wire so we had a wiring problem, specifically an open circuit.  This wire does not supply power to any other components (according to the wiring diagram) so the fix in this case will be to disconnect the wire from the circuit breaker and the switch, cap it at both ends, and run a new wire; but that will also be a project for another day.

By the time we got all of this done it was 5 PM so we decided we were finished for the day.  We cleaned up a bit and went to Pizza Hut for dinner.  There are only two chain restaurants in town; the other one is a McDonald’s.  Angelina Mia is OK, but we had already been there a couple of times.  The Ivy House is reputed to be the best restaurant in town, but when Linda and I checked their menu we did see anything we could eat even with ingredients left out.

John and Marian dropped me back at the coach at 7 PM and headed for home.  I wandered over to the fire pit with a glass of Moscato white wine around 8 PM and relaxed for a couple of hours.  The fire eventually died down and the air got cool so I returned to the coach and worked for a while on the Cool Cruiser article before turning in for the night.