I received a light tower off the repair line with a complaint that a service light goes out intermittently. There are four service lights on this piece of equipment. Each light has it's own capacitor, step-up transformer, and bulb. It shares a breaker switch with one other light, and there are a number of places a problem can occur. I began troubleshooting at the capacitors with my meter and they all had the proper voltage except when the light would go out obviously. I tested them by changing the wiring for the service lights to different capacitors to see if the problem would follow to a different service light. When it didn't I troubleshooted the step-up transformers and they all were reading the proper voltage output. I continued by switching those transformers to different capacitors to see if the problem would follow thereby telling me if I had a transformer problem or something else going on.
It didn't follow to another service light telling me the capacitors and transformers were working fine. Next I checked the generator output at the breaker switches to see if I possibly had a bad winding in the generator. Both breaker switches had a steady 124 volts coming out of the generator and it didn't drop suddenly which would be an indicator for a generator issue. I shook all the wiring harnesses up to the service lights to see if maybe I had a short to ground somewhere but I couldn't induce a problem. I removed the light bar by the service lights because often times someone doesn't reassemble them properly and wires get rubbed through and ground to the frame.
Didn't find anything so I continued troubleshooting by switching service light wiring at the light bar with grounds from different service lights to see if I had a problem in the wiring from the light bar to the actual service light. Problem didn't follow so I knew the grounds were good. Keep in mind the very first thing I did was check power and ground at the service light elbow right before the service light.
This brought me to the conclusion that the problem was somewhere between the elbow and the actual light bulb itself. I had either a bad light fixture or a bad bulb itself. I switched the bulbs in the service lights to see if the problem followed to a different light. It did and all this dummy had to do was change the friggin light bulb...ugh.
So from now on when I have an intermittent problem with a service light I learned to swap the bulbs around..after checking power and ground at the load of course. One must go to the load as a wise man once said.
40hr
400hr
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| Service light wiring in light bar. Power, ground, neutral. |
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| Capacitors on the left and transformers on the right. |
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| Breaker switches |
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| Elbow at service light |
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| Light bar disassembled |
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