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luvdoggiez 03-20-2012 10:02 PM

Keep blowing instrument light fuses
Hi there everyone,

We have an issue in the dash of our Alegro bus that is on a Freightliner chassis. Any suggestions or insight would be greatly appreciated!

Each instrument on the instrument panel, have a light that turns on with the head lights. It seems that these dash lights are grounded out. We keep blowing the fuse for the Dash lights. When we turn on the headlights/marker lights, the dash lights will come on real bright for a second and then the fuse will blow. I've placed a VOHM meter in one side of the fuse slot and found 12 volts. The hot side seams to be sourced from the Marker light fuse. When I place the meter on the other side of the fuse slot, I get 1.4 ohms resistance, which I interpret to mean I have a hot lead shorted to ground some where.

Our Allegro bus is a 2003. Someone suggested there might be a failing control board, but I can't find such a board.

Any suggestions on how I might approach this? I have some ideas, but I welcome any suggestions.

Thanks! - Eric -

Skip426 03-20-2012 10:52 PM

If the lights come on full illumination then the fuse blows , I would suspect that the dimmer is at fault. A dead short it the wiring or the bulbs , should blow the fuse before the bulbs light up. Do you have a seperate dimmer control or is the dimmer part of the headlight switch ? Quick way to check , pull the bulbs , if the fuse still blows 99% chance it's the dimmer.
Good luck.

HeapBigEngin 03-21-2012 12:44 AM

I agree with skip426. Any dead short to ground should immediately blow the fuse.... they don't waste any time going away. The dimmer switch is an intersting idea.

It does sound like something could be "heating up" rapidly, drawing too many amps and then blowing the fuse. And that does not sound like a dead short ground. Bad headlight switch perhaps? I would first check the amperage of the fuse and ensure that it is correct for that circuit. Also, do you have any other items (such as accessory, gauge or radio lighting) that have been wired into that circuit and could be acting up and drawing too many amps for the fuse in that circuit? Electricity and I don't always communicate too well. But I would be thinking current draw and amps, not dead shorts. Am wondering if you could use your multimeter and check amp readings at various points along that circuit, if that is possible.

Hopefully someone else will chime in with more insight. PLEASE let us know what you find out here....Thanks!

luvdoggiez 03-29-2012 06:22 AM

Hi there everyone,

Well, this electrical problem with the Dash lights has been bugging me for a while. We had a family friend come over who had worked on car stereo installation for 7 years. He tracked the problem down to the fact that there were some after-market dash lettering lights (on the switch panel) that were probably causing too much current to be drawn through the fuse and blow it. When we placed those after-market lights on a seperate 10 amp fused circuit labeled 'Extra', and returned the original Panel lamps circuit to a 10 amp fuse, everything seems to be in good shape. We added lighted switch to the Extra lead so that I get the additional reminder that the after-market lights are on. Also, the extra circuit is only 'Hot' when the ignition is on.

Thanks everyone for their feed back, I'll keep it in mind going forward.

Happy camping! (Again!) Eric and Carol

HeapBigEngin 03-29-2012 02:26 PM

luvdoggiez....thank you so much for the update.

So it was an amperage problem after all. That's sure what it sounded like to me. Cool. Way too many times, forum posters with a problem ask for help, get a lot of good suggestions....and never return with the results. Hence, none of us learn anything from the experience. Thanks again for getting back to us, and glad you resolved the issue.

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