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Ambulance back from the mechanic and first electrical exploration
2015/07/24 The ambulance returns from the mechanic.
I picked the ambulance up at the mechanic this afternoon. It has six new tires and two passable spares now. Three of the belts under the hood are replaced with nice shiny new ones, and the fourth has been left off. It's job was to drive what the mechanic described as two pumps for pushing air through the exhaust system to improve emissions scores (without actually reducing emissions). Further research indicates that one of them is an air pump and the other a small combustion chamber, designed to burn any remaining fuel vapor in the exhaust before it escapes. I need to figure some more things out about the engine to find out if I need to reinstate those devices, or I can leave them inactive and remove them, or if I need to cap the hoses leading from them to avoid an exhaust leak. He added adapter fittings to the A/C, flushed out the R12, cleaned the system, and filled it with R134a. He says there's a tiny leak somewhere that he couldn't find, and that I should drive it until the A/C diminishes in effectiveness, which might take weeks or months, and then have it tested with the fluorescent leak-finding fluid. Until then, I've got working A/C again, ice cold out of the vents and cooling down the cab quickly! At this point, the least-cold part of the cab is the doghouse, and I need to investigate putting insulation inside or outside of it, to keep the cab (and especially the humans' legs!) cool. The A/C isn't really enough to cool the box, but it has its own cooler that I need to investigate once power is restored. On that note, with charged batteries and some shade I was able to see that the "Master" toggle switch on the dash does have an indicator light that works. The mechanic says that the high current relays and solenoids in the wiring box should have very audible clicks when engaged, which they don't. That means the wiring fault is somewhere between the dash and the box, which does narrow it down to about 1/3 to 1/2 as much ground to cover as I had before. It drove home just fine. Tomorrow morning I'm going to try to take some photos, get the one odd lock rekeyed to match the keys I have, and maybe trace some wires. I might also drag one of the batteries to the box and wire it into the system directly so I can test some of the components prior to getting the main wiring working.
2015/07/25 Let there be light!
This morning and evening I again had trouble getting it to start. Trying to crank it results in the starter turning the engine over just fine, but it doesn't even pretend to try to fire. Applying some patience, I tried again after 20-30 seconds, still no dice. Another try a minute later led to it firing once then winding down. Then the fuel pump(?) started to run, and about 20 seconds into that sound I tried again and it started... then died again 10-15 seconds later. Two more cycles of that and it started and kept running. I do need to investigate this more seriously. Since it does eventually start up quickly, and always starts quickly when it's not cooled off, I'm hopeful that this will be an easy problem for a seasoned mechanic to recognize.
This evening I took the dash switchboard apart. Lo and behold, the folks who disconnected the police/ambulance lights DID leave some wires disconnected that they shouldn't have. I went back to the big wiring panel in the back to check which wire[1] activates the master solenoids/relays, confirmed that one was one of the disconnected ones, plugged it in, and things started working! The master switch now engages the two big solenoids with a loud "clunk", lighting up the indicators on the switchboard. The dome lights in the box work. One (of three) floodlights on each of the left and right work. The reverse safety beep thing works. Also, the dash switch for "Stinger" is able to turn on its own indicator, but I don't know what it might do, and doubt the device in question is still installed.
In a stroke of insight, I realized both why the other floodlights don't work AND why they are missing their covers (exposing the lamp and insulation to the elements)... Those lights must have had red/blue covers before and been hooked up to a flash sequencer. I can see where the sequencer was removed from the wiring panel. Funnily enough, there's a second sequencer in one of the other cabinets in the box, so I can probably get that system working again if I want the floodlights to wigwag for a party/parade/etc. In the near term, I just need to trace the appropriate wires and re-connect them directly to the appropriate solenoids to get all of the floodlights working again. I also need to source some covers for them, which may be easy or difficult (or even require custom fabrication) once I find the manufacturer and part numbers for the existing lamps and covers. On a related note, all of the bulbs are incandescent, which just isn't going to fly in 2015. I'll be replacing the interior dome lamps with LEDs as soon as I can stop by a hardware store to confirm that the lamps have BA15d bases, probably replacing the cab/dash indicators, and hopefully finding replacements for the floodlamps as well. In the end, the only incandescent lights in the rig should be the headlights.
With the master power restored, I am much better equipped to figure out what all the other switches, relays, and indicators do. There's a switch on the wall in the box that makes one of the big solenoids thunk but I can't tell which one without a multimeter. There's a lock-switch on the gun rack that makes one of the small relays click, but again I can't tell which one. There's an indicator on the dash for "patient condition", and another for "compartment door", neither of which I can reliably affect the status of, so I'll need to figure out those as well. There's a switch in the box that is always illuminated and doesn't seem to do anything. In addition to a multimeter with very long leads, I may also invest in a wiring tone generator that's compatible with 12VDC wiring, for tracing wires through the walls.f
[1] Almost every wire from the big wiring panel has a number on it, and the other end of that wire, wherever it is, has the matching number. It's wonderful. Thank you, anonymous engineer/installer at First Response Inc! I need to get a set of those number stickers so I can replace the ones that are wearing/falling off as I find them. Having those numbers is saving me time already, and is going to save so much more as I figure out the rest of the wiring.
I picked the ambulance up at the mechanic this afternoon. It has six new tires and two passable spares now. Three of the belts under the hood are replaced with nice shiny new ones, and the fourth has been left off. It's job was to drive what the mechanic described as two pumps for pushing air through the exhaust system to improve emissions scores (without actually reducing emissions). Further research indicates that one of them is an air pump and the other a small combustion chamber, designed to burn any remaining fuel vapor in the exhaust before it escapes. I need to figure some more things out about the engine to find out if I need to reinstate those devices, or I can leave them inactive and remove them, or if I need to cap the hoses leading from them to avoid an exhaust leak. He added adapter fittings to the A/C, flushed out the R12, cleaned the system, and filled it with R134a. He says there's a tiny leak somewhere that he couldn't find, and that I should drive it until the A/C diminishes in effectiveness, which might take weeks or months, and then have it tested with the fluorescent leak-finding fluid. Until then, I've got working A/C again, ice cold out of the vents and cooling down the cab quickly! At this point, the least-cold part of the cab is the doghouse, and I need to investigate putting insulation inside or outside of it, to keep the cab (and especially the humans' legs!) cool. The A/C isn't really enough to cool the box, but it has its own cooler that I need to investigate once power is restored. On that note, with charged batteries and some shade I was able to see that the "Master" toggle switch on the dash does have an indicator light that works. The mechanic says that the high current relays and solenoids in the wiring box should have very audible clicks when engaged, which they don't. That means the wiring fault is somewhere between the dash and the box, which does narrow it down to about 1/3 to 1/2 as much ground to cover as I had before. It drove home just fine. Tomorrow morning I'm going to try to take some photos, get the one odd lock rekeyed to match the keys I have, and maybe trace some wires. I might also drag one of the batteries to the box and wire it into the system directly so I can test some of the components prior to getting the main wiring working.
2015/07/25 Let there be light!
This morning and evening I again had trouble getting it to start. Trying to crank it results in the starter turning the engine over just fine, but it doesn't even pretend to try to fire. Applying some patience, I tried again after 20-30 seconds, still no dice. Another try a minute later led to it firing once then winding down. Then the fuel pump(?) started to run, and about 20 seconds into that sound I tried again and it started... then died again 10-15 seconds later. Two more cycles of that and it started and kept running. I do need to investigate this more seriously. Since it does eventually start up quickly, and always starts quickly when it's not cooled off, I'm hopeful that this will be an easy problem for a seasoned mechanic to recognize.
This evening I took the dash switchboard apart. Lo and behold, the folks who disconnected the police/ambulance lights DID leave some wires disconnected that they shouldn't have. I went back to the big wiring panel in the back to check which wire[1] activates the master solenoids/relays, confirmed that one was one of the disconnected ones, plugged it in, and things started working! The master switch now engages the two big solenoids with a loud "clunk", lighting up the indicators on the switchboard. The dome lights in the box work. One (of three) floodlights on each of the left and right work. The reverse safety beep thing works. Also, the dash switch for "Stinger" is able to turn on its own indicator, but I don't know what it might do, and doubt the device in question is still installed.
In a stroke of insight, I realized both why the other floodlights don't work AND why they are missing their covers (exposing the lamp and insulation to the elements)... Those lights must have had red/blue covers before and been hooked up to a flash sequencer. I can see where the sequencer was removed from the wiring panel. Funnily enough, there's a second sequencer in one of the other cabinets in the box, so I can probably get that system working again if I want the floodlights to wigwag for a party/parade/etc. In the near term, I just need to trace the appropriate wires and re-connect them directly to the appropriate solenoids to get all of the floodlights working again. I also need to source some covers for them, which may be easy or difficult (or even require custom fabrication) once I find the manufacturer and part numbers for the existing lamps and covers. On a related note, all of the bulbs are incandescent, which just isn't going to fly in 2015. I'll be replacing the interior dome lamps with LEDs as soon as I can stop by a hardware store to confirm that the lamps have BA15d bases, probably replacing the cab/dash indicators, and hopefully finding replacements for the floodlamps as well. In the end, the only incandescent lights in the rig should be the headlights.
With the master power restored, I am much better equipped to figure out what all the other switches, relays, and indicators do. There's a switch on the wall in the box that makes one of the big solenoids thunk but I can't tell which one without a multimeter. There's a lock-switch on the gun rack that makes one of the small relays click, but again I can't tell which one. There's an indicator on the dash for "patient condition", and another for "compartment door", neither of which I can reliably affect the status of, so I'll need to figure out those as well. There's a switch in the box that is always illuminated and doesn't seem to do anything. In addition to a multimeter with very long leads, I may also invest in a wiring tone generator that's compatible with 12VDC wiring, for tracing wires through the walls.f
[1] Almost every wire from the big wiring panel has a number on it, and the other end of that wire, wherever it is, has the matching number. It's wonderful. Thank you, anonymous engineer/installer at First Response Inc! I need to get a set of those number stickers so I can replace the ones that are wearing/falling off as I find them. Having those numbers is saving me time already, and is going to save so much more as I figure out the rest of the wiring.