I have the 3 volume factory GM Service Manuals for my 1999 Silverado but have been unable to find the ratings for various switches. For example, the Cargo Light switch is actually a small printed circuit board. There are no ratings printed on either side of the PCB. Where can I find the rating for it? I could look up the light bulb specs, but that would only give a minimum bound for the rating of the switch. How much extra sustained current it can handle safely? For example, my truck doesn’t have fog lights nor a fog light switch. Can I change the cargo light switch to turn on/off fog lights? I suppose the best option would be to buy a new assembly that has switches for both the cargo light and the fog lights, but I’m too much of a penny pincher to do that. Alternatively, I guess the safest would be either to to power the fog lights through a relay activated by the cargo light switch (repin the connector), or to install a generic toggle switch on the dash.
Anyway. I don’t really have plans for fog lights. That is just an example. I’d like to know about the amp rating for the cargo light PCB switch in particular, but I’m also asking more generally about how to find rating info.
I do not know of any publication that lists the amp rating on oem switches. I would always consider the load being placed on the switch it was designed for. The cargo light switch directly controls two bulbs that should draw about 2 to 3 amps total so I would expect the switch to be rated for at least twice that. The fog light bulbs would draw about 7 to 10 amps total so the oem cargo light switch would not be able to handle that load. Of course the oem fog light switch would not either and they merely use that switch to control a relay.