High Mount Center Stoplight

[CareyWeber]

I want to add a high mount center stoplight on my horse trailer. I'm using a seven wire RV plug. Light trucks and auto use the same lights for both turn and stop lights. Can I tap into my trailer brakes and use that to trigger my high mount center stoplight, so that it only has tail light and stop functions?

Carey

[DmaxMaverick]

You may be able to get a module to do the job. Check with Napa.

If you use the electric brake circuit, it will not be consistent with your brake lamps because they don't get full battery voltage, apply gradually, and delayed. At low gain, it may not illuminate the lamp at all or be very dim (not worth the effort, and not effective as a CHMSL). If you use a relay, at low gain (less than full brake application), it won't likely excite the relay to trigger the lamp.

If you want to make your own, it isn't too difficult. You'll need an insulated lamp fixture (not grounded, with + and - leads), 2 relays (inexpensive at Radio Shack, a little more at Napa), and some wiring stuff. Wire one relay, energized by one signal circuit to supply + to the new lamp. Wire the other relay, energized by the other signal circuit to supply - to the new lamp. That way, it will only illuminate when both trailer signal lamps are energized (brakes and hazard flash), and it won't flash when one of the turn signals are used (like I've seen so many installed). Or, you could wire one of the connector legs into your CHMSL circuit on your truck to the trailer, but then it would only work when your truck is towing that trailer. Using the relays, it would work with any tow vehicle, even if it doesn't have CHMSL.

[CareyWeber]

This the LED light I'm planing on using.

http://www.grote.com/product.php?product_number=49252

[DmaxMaverick]

.06 amps is not going to effect any circuit you tap. The lamp you selected looks fine, and appears to have 2 luminosity leads, so be sure to use both leads for the brake lamp. If not, it'll be too dim. Verify this, or it may be too dim for brake lamp use (marker lamps have about 1/3 the luminosity of brake lamps). The lamp is very small, less than 1/4 the area of "normal" CHMSL's (1/2 as high, 1/2 as long), so the luminosity is important to be effective. It should work, though, as long as it is bright enough. They don't list the candle power (should be about 75).