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Old 02-01-2019, 08:43 PM   #1
Mini-Skoolie
 
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Tail lights work intermittently

I have a 2002 Thomas e450 short bus. The tail lights, marker lights and the school bus cluster all go off then come back on. Sometimes they will shut off for a second sometimes for an hour . They will do this sitting still or while driving.

You can hear the relay click when they go off and click when they come back on. All other lights stay on when this happens. It also looks like the tail lights were replaced recently. They are a square shaped with two lightbulbs one on bottom and one on top. The top one never comes on.

I understand household electric( to a certain degree) but I've never dealt with auto. I'm assuming my problem is a short before the relay. How would I go about finding it? How does the wiring run? If anyone has any advice or tips I would greatly appreciate it.
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Old 02-01-2019, 08:54 PM   #2
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Originally Posted by Apud View Post
I have a 2002 Thomas e450 short bus. The tail lights, marker lights and the school bus cluster all go off then come back on. Sometimes they will shut off for a second sometimes for an hour . They will do this sitting still or while driving.

You can hear the relay click when they go off and click when they come back on. All other lights stay on when this happens. It also looks like the tail lights were replaced recently. They are a square shaped with two lightbulbs one on bottom and one on top. The top one never comes on.

I understand household electric( to a certain degree) but I've never dealt with auto. I'm assuming my problem is a short before the relay. How would I go about finding it? How does the wiring run? If anyone has any advice or tips I would greatly appreciate it.

the first thing I'd check is the ground
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Old 02-02-2019, 03:32 AM   #3
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Thanks. Turns out the tail lights have plastic housings and there isn't a ground wire anywhere.
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Old 02-02-2019, 10:12 AM   #4
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Please post some pics of the lights and wiring.


The noise you hear is more like a breaker tripping, no relays involved.


Each light socket must have a ground that is common and connected to each socket then the final ground connection could be hidden somewhere else in plain sight.


Without testing you won't learn anything looking at this problem.


John
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Old 02-02-2019, 02:59 PM   #5
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https://www.flickr.com/photos/162861...posted-public/
https://www.flickr.com/photos/162861...posted-public/
https://www.flickr.com/photos/162861...posted-public/

The white wire runs from the top ( non working) light down to the bottom and out thru the back. It gets no power. The other two wires are brake and running lights. As of right now they are both working. They both are getting 12 volts. The light housing is screwed into fiberglass on two of the bolt holes and the third runs thru the fiberglass and steel it had a washer on it and if I test there it's getting ground.
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Old 02-02-2019, 03:34 PM   #6
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The pic of the rusty hardware is not conducive to good grounding, so they need to be in as new condition first. The pics don't help much but maybe the ground goes all the way back to the switch for those light then to ground.
Maybe not but still a possibility.
The connection using mounting holes for grounding on fiberglass is most likely the culprit. Make a new ground point on the chassis somewhere close and try the operation of the lights. If they stay on make it permanent.


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Old 02-02-2019, 04:01 PM   #7
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Will do thanks
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Old 02-02-2019, 04:28 PM   #8
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So when multiple lights go out, in my experience, it's likely the ground wire. This is especially true if intermittent. Wire is likely drifting around and finally resting against metal when it is working.
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Old 02-02-2019, 05:14 PM   #9
Mini-Skoolie
 
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So what is the best way to ground these out? They are plastic housings. Should I run a wire to the socket?
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Old 02-02-2019, 05:29 PM   #10
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So what is the best way to ground these out? They are plastic housings. Should I run a wire to the socket?

Each socket will differ in number of wires.

Some 2, some 3 wires, one is ground in plastic crap.

One should be ground for that fixture. Simple test tells that.
Do the same for every socket then connect all the ground wires to your eventual newly installed ground wire.
Hope you know how to make a good connection for each.


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