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  Rubber-covered Switch Gets Hot, Melts Rubber

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Author Topic:   Rubber-covered Switch Gets Hot, Melts Rubber
masbama posted 10-02-2010 10:09 AM ET (US)   Profile for masbama   Send Email to masbama  
My 1999 Dauntless 18 has rubber-covered accessory switches on the console. The last one on the right, which is for the depth finder, gets real hot and has melted the rubber portion when turned on. Is this just the bulb or the whole switch? This just started to happen. Thanks!


Jefecinco posted 10-03-2010 11:09 AM ET (US)     Profile for Jefecinco  Send Email to Jefecinco     
Generally, high resistance causes heat in circuits. I believe the rubber boot is a cover for the circuit breaker reset button. The circuit breaker is supposed to protect the circuit from overload/overheat with resulting damage to the wiring and/or device protected.

The heating could be caused by a a deteriorated, high resistance connection, a cross connection due to frayed conductor insulation, a bad circuit breaker, or a defective depth finder. Other causes are possible but I believe those mentioned are most likely the cause.

Personally, I prefer not to connect a depth finder to a helm switch. The switch on the device serves well for turning the unit on or off. I recommending bypassing the helm switch and installing a normal in-line fuse to protect the depth finder. If you do this carefully check the conductors and connections before energizing the circuit.

If you choose to bypass the helm switch I also recommend you replace the circuit breaker below it because it has badly overheated and may no longer be effective. I'd replace the boot too as it will probably crack and lose water tightness soon.

masbama posted 10-04-2010 10:17 AM ET (US)     Profile for masbama  Send Email to masbama     
jimh posted 10-09-2010 10:26 AM ET (US)     Profile for jimh  Send Email to jimh     
The power drawn by a depth sounder is not very great. I would expect that at 12-volts a depth sounder would only draw a few amperes. Because the depth sounder apparently continued to operate, we have to assume that most of the power flowing in the circuit was delivered to the depth sounder and was not lost in the switch contacts. In a circuit with 36-watts of power, if we allow even 20-percent to be lost in the switch contacts, this is only 7-watts. I do not think that 7-watts of electrical energy converted to 7-watts of heat and dissipated over the area of a typical dashboard mounted circuit breaker or switch would be capable of melting rubber. I suspect that there is another short-circuit path in this switch which is creating the heating. Discard the switch and replace it with a new one.
jimh posted 10-10-2010 10:10 AM ET (US)     Profile for jimh  Send Email to jimh     
Also, as recommended previously, check the wiring in the circuit for other loads or shorts which could be creating a high-current draw.
masbama posted 10-13-2010 09:52 AM ET (US)     Profile for masbama  Send Email to masbama     
Thanks to both!

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