| Subject: Re: T500 Lighting circuit - How many Amps? |
Author:
brian henry
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Date Posted: 21/02/06 14:35:25
In reply to:
Neil
's message, "Re: T500 Lighting circuit - How many Amps?" on 21/02/06 9:54:20
You say you have a new replacement light fitting so the spade lugs should not be a cause of the high resistance you imply. It is easy to replace the female lug contacts on the cable to the fitting, just cut off the old and crimp new ones on, they are easily available. Then check if you have 12 volts across each of the two contacts before sliding them onto the light fitting lugs.
If not, trace back to the relevant circuit breaker and if you have 12 volts across the output of that and the ground connection. If you do, disconnect the battery and check for continuity of both lamp connections back to the circuit breaker and the ground connection. Use the multimeter on “Ohms” with a high resistance scale for a connection. If you have an open circuit on either you need to change the cable; use the original as a pull-through.
If you do have 12 volts across the input connections and the lamp still does not light then you must look for the problem in the fitting itself. The original fittings have a temperamental switching mechanism where the rotating, translucent dome has a cam that bears on a metal strip as it turns to force it against another metal strip to complete the contact to the light bulb(s). Check that this contact does indeed make a connection, use your multimeter for continuity with the power removed, very often the contacts will get dirty or corroded and prevent electrical contact, but with a new unit this will be unlikely. The idea of the flexible metal strip is that it can be forced firmly against the equally flexible static contact, resulting in a sliding effect that provides some self-cleaning, necessary in a marine environment. However, older units have sometimes had tampering where the metal strip has been "adjusted" to give more (or less) pressure on the complementary contact strip and then they never properly meet and make good contact.
I personally dislike these light fittings and the time that I had to replace one I chose to do so with one of a similar size and appearance but with a toggle switch set in the rim, it was altogether better in quality, appearance and maintenance-free operation – and cheaper to boot.
Forgive me if all of the above sounds too much like stating the obvious, but your original posting gave the impression that you were not too familiar with electrical matters and at the same time rather frustrated.
Best, B.
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