| Author | Message | ||
| R.C.Bishop
Rating: N/A |
I hesitate to post this because it is very difficult to explain what is going on and what I might have done to cause the problem, but please allow me a feeble attmept at explaining....any comments (keep 'em positive, please  )will be appreciated. I have kept the lounge lights (over the seats) and recently made an attmept to change them from the start batteries to the house set. These are two lamps,in one fixture where the seat was. I have retained about 6 fixtures down the driver side. I ran new wire, severed all former connections of those retained. Any that were not used were severed as well, including the connection to the switch and ground. All severed ends were taped. The new wire is connected to a "buss bar", properly insulated from the chassis, where the house set furnishes the current....the line is fused after leaving the "bus bar"prior to making the run. It runs the length of the coach and is interrupted wherever a fixture ( with it's own switch) is attached. A battery negative wire also runs the entire length, uniterrrupted, and is grounded at the front end, as well as the rear, of the coach. This wire is directly connected to the wire from the battery set on a terminal strip. The light fixtures are metal. When they are just "hanging"....not attached and in place I get a reading of anywhere from 0.04 to 0.12 or so when I test voltage at the fuse block (fuse removed, of course)....NOW here's the catcher.....when I install, or ground the metal lamp box to the coach, which is a metal chase, I get a current reading of 13.4 volts...no fuse as above. I have worked and reworked and re re worked this thing from front to back...even connecting each lamp to the battery negative line....but alas,13.4 volts. There are no damaged wires, nothing that is apparent that would cause a problem. I have other runs ( sump pump, heaters, etc) with which I have had no problems. Where in the world could the problem (short) be? Thanx for indulging me>>>>>>> RCB | ||
| Tim Strommen (Tim_strommen)
Rating: N/A |
A couple of questions: 1) For your electrical system, is it 12 or 24 volts? Positive or Negative Ground? 2) When you ge the 13.4 Volt reading, is the engine running? 3) When you take this reading is the switch on? 4) Accross what are you taking this reading? (i.e.: between the chassis and the case, across the switch, at the fuse terminal between + and GND?) 5) Did you "tape" severed ends together or all of them separate? While you ponder and reply to those questions, Your bus is most likely a negative ground, so attaching the fixtures (which are metal and therfore conductive) are probably negative ground fixtures. If you have a negative ground vehicle, and you've run the ground wire to all lights - the ground wire will be redundant. To make these lights work, you will need to make sure that the power is switched on the HIGH-SIDE ONLY. Obviously switching the power on the low-side wouldn't make much sense if the base of the bulb holder is riveted to the metal case (and there again completing the circuit to ground - powering on the lamp). If you have a standard automotive-type interior light, by examining the fixture construction you should be able to succesfully determine the wiring format. By looking at the bulb socket, you should be able to determine if the base is electrically connected to the metal case of the fixture. If so, you will want to trace the conductor exiting the base of the socket to a switch. Tone out (using an ohm-meter) which spade lugs or screw terminals of the switch are electrically switched and hook the opposing terminal to the positive bus wire you ran. You should then have 13.4 when the switch is on, and ~0V when off accross the bulb contacts (also a bulb should work correctly). You will need to check each fixture individually, as a single mis-wired switch can lead to a direct short. Of course if you have a positive ground vehicle (and quite a few still-running busses are...) you will have to reverse the electrical connections (don't take the ground on an old bus for granted). I'm interested to see what you find. Cheers! Tim | ||
| R.C.Bishop
Rating: N/A |
Tim...thanx... 1)12 Volts, negative...2)No....reading taken at the fuse box, between the poles,(no fuse)...3) hard to tell, but generally, I would think, "no" (multiple switches)...4) the right fuse terminal is to battery Pos....the left is the wire that goes the length of the coach, attached to each lamp fixture......5) all ends separately taped off regardless of + or -. Will do as you suggest with each fixture; each switch.....the wires at each switch (2) are soldered, enclosed in a very small metal box. Thanx for the feedback. BTW. I note that on another wire, run to the opposite (curb) side and attached to nothing at the far end...different wire and in no way connected, except battery negative, shows a .09 volt reading done in the same manner as the lighting. They are on no way connected, except, as stated, the battery negative. The far end is attached only to a terminal strip...nothing on the opposite connector of the strip. Everything else in both sets (14 wires, 2 cables of 7 each) reads 0.00 volts. Some are energized...some not. Got to be a conflict in the chassis, somehow. Wierd! Thanx again. | ||
| David Hartley (Drdave)
Rating: N/A |
I didn't notice what coach you are working on, if its a 24 volt coach then; Are you getting the 12 volt ground for that line from your chassis batteries? If for instance you are and your chassis batteries are set up for 24 volts and you have grabbed the (high) side group or ( 24 volts referenced to chassis ground) that would explain exactly what you are seeing. I will explain; On most 24 volt systems there are two taps. The first one at the 12 volt terminal ( between the first battery and ground ) The second or (high) 24 volt tap is taken from across both 12 volt batteries in series.( This is usually for coach electronics and starter.) If by chance you actually tapped into the ( high side) or second battery set you would always see a -12 volt reference to the 24 volt high side tap and not truly between the chassis ground and the secondary ground wire that you added. This is caused by a reverse feed from the +24 volt circuit. If this is what happened, plan on letting the smoke out of something as you are creating a short between your batteries and the 24 volt system. The obvious stuff takes more effort to unravel than the simple stuff. Everything (d.c.) in any coach should be referenced to absolute chassis ground. Not to an auxillary ground wire which might be connected to the wrong battery terminal. Put a great big ground cable from the negative terminal of your house batteries to chassis ground. Try not to use a floating (negative) anywhere you don't need it. It will only cause confusion. | ||
| Craig (Ceieio)
Rating: N/A |
Hmm, your reading across the empty fuse holder is about what I would expect to see. With no fuse in the holder, one side of the fuse holder is connected to the battery, and the other side has no power source, thus a potential difference. Re-measure everything referenced to ground to see that you are really dealing with. This should rule out any 24 volt source cross connect (or not). If one side of the holder is 13ish volts and the other is close to zero, that is to be expected. Next if the one side is really close to zero volts, take a resistance measurement between that side and ground. Do this to rule out a short to ground on the buss bar and related connections. If you get zero ohms readings you have a short and you can systematically break connections until the short to ground goes away. Craig - MC7 Oregon | ||
| R.C.Bishop
Rating: N/A |
Hey youse guys, this is a 12 volt system... Lotsa good info here and I thank you...worked all day on it and completely rewired( reconnected) everything....still about the same readings.... problem is, it blows a 15 amp fuse instantly.(Not all circuits; just the one reading 13.4 volts) Thanx for the continued input. RCB | ||
| Tim Strommen (Tim_strommen)
Rating: N/A |
Hey R.C. Sorry it's taken me so long to get back to this post... Okay, I re-read your first post, so I'll try and restate everything you said over two posts so that it makes sense: 1) When your fixture is connected with the +/- terminals, floating (not mounted), and switched off - and you measure accross the fuse block you get no (or very marginal) voltage drop. 2) When your fixture is connected with the +/- terminals, MOUNTED, and switched off - and you measure accross the fuse block you get 13.4 volts (indicating a dead short). If both of these statements are true, then my best guess is that you have the wires backwards on one or more fixtures - and the fixtures (and bulb socket) do have a negative ground to the chasis. This would look like a wire to electicity and the fuse would be the weak point (thank goodness too!). The only other possibility is that the terminals are coming in contact with the chasis behind the fixtures, or you pinched a wire between the fixture and chasis. Your your hot wire could have a short to ground (bad insulator) but since the problem only occurs when you mount the fixtures, it's not as likely as the other possibilities. You can take a continuity reading accross your fixtures positive terminal (which you would hook up to the +12VDC wire) and the fixture base both with the switch on and off to see if it's making a complete circuit (you need to remove the buld for this test). If you get continuity, you should only have to reverse the wires from the bulb base to fix this. If not, then check inside the hole where the fixture mounts to see if there are any scratches indicating where a terminal may have made contact. Also - double check that you don't pinch any wires when mounting the fixture (you will see a flat impression made in a wire and maybe some exposed copper if this happened). If you're still having trouble, let me know - electrical gremlins are fun to me! Cheers! -Tim | ||
| R.C.Bishop
Rating: N/A |
Hey Tim....Rob( off line) Dr. Dave and Craig....many thanx for your responses and your interest. As a matter of fact, I went thru the 12 volt system completely on Saturday, changed a few things and made sure all fixtures were gounded. The batteries are chassis grounded within a couple of feet of the bat set.....tightened connections, put all applicable systems on 12 volt House bats and generally overhauled the whole thing, adding fuse blocks at the same time and in one location only. Have absolutely no idea where the problem was but now every system on that side is working. Get readings across an empty fuse block of any where from .04 to .21 depending on the circuit. This with all switches off. Turned on everything on 12 volt and all works fine. I suspect that the problem was an inter-connection somehow/someplace between the starting system and the house system. They are now, far as I know, completely seperate systems, with exception, of course of chassis ground for both. To expain, I am using switches that were previously for the starting battery setup, now isolated to the housew system. All's well that ends well..... now to just get the isolator to charge each system properly.... Many thanx again to each of you. RCB '64 Crown Supercoach (HWC) | ||
| Tim Strommen (Tim_strommen)
Rating: N/A |
Glad to hear it worked out R.C.! -Tim |