Interior van fluorescent lights not working

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Old 01-06-18, 02:54 PM
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Interior van fluorescent lights not working


Hi gang, I have box van work truck that has a strip of fluorescent lights down the middle of the ceiling. They have been broken for years and I am now trying to fix them. I have been tracing back the wiring with my multimeter and checking for broken wiring. There is a dedicated wire coming off my car battery terminal, passes through a fuse, which I replaced, and a door switch on the way to the ceiling fixtures. I am getting 12 + v coming out of the switch but only 0.3 v when I test off of the fluorescent fixture itself. Aha! I think, I have a bad wire, but when I string a new wire straight from the switch to the light fixture I go back to 0.3v. Now I'm lost. I have four fixtures on the ceiling and this wire is the common hot to all the transformers. I can see one being bad but not all four. I tested continuity on the bulbs and they seem fine. No ground wire to find because they are all grounded against the metal of the box van.

I guess I just know enough tot get myself in trouble. Any advice?
 
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Old 01-06-18, 04:03 PM
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I've done a ton of servicing work in motor homes. I've chased many fluorescent lighting problems. They've always been a nuisance. Low light output with low voltage, won't light when cool or cold, short tube life, etc.

Now I replace them with LED fixtures.

There is a +12v line to the fluorescent fixture ballast and many times the ground comes from the metal case. Make sure the ballasts or the fixtures are actually grounded. If you have 12v on one end of the wire.... it should appear on the other end. You should be checking from that wire to a known ground to make sure you have power at the light.
 
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Old 01-07-18, 02:34 AM
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sounds like maybe a bad switch depending on how your testing the circuit just checking for voltage is not a very good test of the circuit, doing a voltage drop test on the switch and wiring may lead you to the problem.
 
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Old 01-07-18, 12:40 PM
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Continued..

I bypassed the switches and still the same problem when i direct wire them. Voltage is still dropping out. Bulbs are Phillips F15T8CW 15 watt fluorescents. Still confused.

I am pursuing just swapping these out for LED but I am having trouble finding large LED strips of equivalent size and brightness that are D.C. It seems that all the ones I'm finding at auto part stores are too wimpy and the ones I'm finding online or at hardware store are for home use and 120v with a transformer. Can I use the same stuff and just forgo the transformer? What is the operational tolerance of such things. Do I need to match the voltages exactly?
 
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Old 01-07-18, 01:27 PM
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to do a voltage drop test you would put the volt meter leads on each side of the switch or each end of the wire your testing and read the voltage under load or when the lights should be turned on if the voltmeter reads any significant voltage its indicating high resistance and the cause of a voltage drop a good connection should be .2 volt or less
 
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Old 01-07-18, 01:54 PM
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a quick search on amazon for led van light showed several options for 12 volt led lights they likely wont work with only .3 volts either though would be prepared to run new wiring though or fix the existing circuit.
 
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Old 01-07-18, 02:00 PM
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You need to find out where you are losing the voltage. If you have it at the switch but not at the end of the new wire..... the new wire is bad.
 
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Old 01-07-18, 02:38 PM
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You ran the new wire and tested voltage at the end of it OR did you test the fixture again with the new wire run. You could be providing 12V to the fixtures, but have an issue inside...corrosion, poor connections or bad grounds. You say there are 4? Are they a series or in parallel?

Can you take the fixtures out and bench test individually?
 
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Old 01-07-18, 02:48 PM
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So I removed the switches from the equation, by unwiring them completely. I install a new test wire from my battery and I have 12v at the end of the new wire when I put my other test lead against the metal truck panel walls. I take that same wire and install it to the supply wire an inch in front of one of the ballast transformers and the voltage drops, The wiring that feeds all four fluorescent fixtures is wired in parallel.
 
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Old 01-07-18, 03:05 PM
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now with photos

Screws all over the back of the housings directly into the metal roof of the box. I get good ground when I touch the lead to any other place on the ceiling.

Here are some photos of what I have.

https://www.dropbox.com/s/qabxs3m0zy..._4965.JPG?dl=0
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https://www.dropbox.com/s/2lzi6obr8q..._4966.JPG?dl=0
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https://www.dropbox.com/s/6mivwhvrng..._4967.JPG?dl=0
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Last edited by PJmax; 01-07-18 at 04:05 PM. Reason: added pics from links
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Old 01-07-18, 03:07 PM
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Can you isolate the common wires to each and give 12V one at a time to see if any fire up individually?
 
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Old 01-07-18, 04:07 PM
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In the center picture of the ballast/supply..... is the positive and the negative marked on the board. ? Usually white is 12v+ and black is ground..... but not always.

Those fixtures don't look like they get their ground thru the metal chassis.
 
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Old 01-07-18, 04:23 PM
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Look at the corrosion on the board...internet diagrams list the ballast case as a ground. Just like battery corrosion, I would remove and clean all contacts. That could very well be the source of your resistance because you're getting voltage though but, something is hindering the full current.

Also I am not sure because in auto, red is +12, black is ground and yellow is switched 12 or memory at times.
 
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Old 01-07-18, 04:31 PM
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The board is not connected to chassis. There is an insulator between the board and the metal. The semiconductor that is riveted to the metal chassis is electrically insulated from the chassis also.

I do agree that the board looks well corroded.

Those fixtures were probably designed to work in a positive or negative ground vehicle.
 
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Old 01-21-18, 10:34 AM
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Led

I took the suggestions above and decided to rip out the fluorescent bulbs and ballasts and start over with LED. The price for 80 LED lights in two strands was the same cost as about four replacement light bulbs so I went for it.

Next problem. I installed a 40 LED strand, directly wired from my battery leads to cut down on the variables. Everything worked fine, lights were super bright. Being satisfied with that I went to wire up the switch near the van door. I accidentally brushed the hot wire against the chassis and now the lights are only dimly bright. WTH. I saw no sparking or arc did I just fry the LED strand? Everything else in the van works fine, interior cab lights, radio. Still getting 12v from battery lead when ground to the chassis so I don't think I blew the in line 15v fuse but when I test with multimeter through the light strand i am down to 5.6v. Any further advice?
 
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Old 01-21-18, 10:41 AM
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When connecting directly to a battery..... there needs to be a fuseholder at the battery to protect the circuit. You said 15v fuse. Did you mean a 15A fuse ? That should have blown. Touching the hot wire to ground should not have damaged the LED's. When checking voltage at the end of the wire at the LED's..... the LED's need to be connected to the wiring as a load. You need to measure 12v between your hot wire and what ever you are using as ground.
 
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Old 01-21-18, 11:17 AM
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Yes, 15A fuse. I misspoke. Is 15A fuse the correct size for this application?
 
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Old 01-21-18, 11:23 AM
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A 15A should be perfect. It's there to protect your wiring from shorts. If you didn't have a fuse protecting that wire connected to the battery.... the wire would heat up until it burned open if shorted to ground.... usually causing a fire.

It would only take a very brief short to open that fuse so my guess it may be burned open.
 
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Old 01-21-18, 11:29 AM
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Then why am I getting any power at all? I'll go look but it's a wet crawl so I'm stalling.
 
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Old 01-21-18, 11:41 AM
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A wet crawl ???

The fuse should be at the battery. Is your battery under the vehicle ?

This is a very basic application. A 12v battery and lights. A wire from the + battery post to the lights and I'm guessing you're using the chassis as ground. If you have 12v at the battery from the + post to ground but not at the end of the wire.... the problem is fairly simple. The wire. If you want to run wire that won't give you trouble.... use #12 THWN/THHN which is single conductor electrical wire. There should not be any splices in your battery wire.
 
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Old 01-21-18, 02:59 PM
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We have resolution.

This is a custom work van so the battery compartment is down low underneath. Yes, a bit wet lying on the ground to get to.

The problem was with the fuse block, wired right off the battery terminal. When I was wiggling it the lights would flash. I removed and replaced the fuse housing. Everything works gorgeously. I guess I was confused before by the fact that I was still getting 12v at the hot wire where it attached to the lights. That v would drop to about 5v when I added the lights to the loop and I tested from the end of the lights to the chassis. Bad wire causing resistance? Would that be the correct way to explain it?
 
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