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need schooling on choosing a diode

ehall

ehall

NAXJA Member
NAXJA Member
Location
Southern Maryland
I am going to try putting a diode between the cargo lamp and the rest of the interior lighting harness so that opening the hatch will only cause the cargo lamp to activate and not the rest of the interior lights (if this works, I'll wire some hatch work lights into the cargo lamp portion of the circuit). However I have no idea of which diode to buy.

I have read on wiki about diodes but that info is all low-level tech and does not really talk about the practical aspects. I have also read around the interwebs about people doing similar things for fog lights and daytime running lights and whatnot, but those are much higher wattage than the application, and none of them really explain how to choose a diode.

I know Radio Shack has what I need, but no idea which one or what to look for or anything. Basically I'm looking at at 10 amp, 12 volt circuit. Where to go from there?

Thanks for any help
 
Diodes are rated in amps and PIV(peak inverse voltage).So a diode with a PIV of 20Volts or more would be fine on a 12v car system!Your also looking for a Power(rectifier) diode.
 
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200 piv does not give you the amperage it can handle, the lower the voltage, the higher amp requirement for a given wattage.
 
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ehall said:
sorry one more--since there is no operating voltage and instead just a peak voltage, I assume that the amperage is for the peak voltage. IE, a diode rated for 3 amp 200 piv can carry 50 amps at 12volt?
Click to expand...
Doides are not based on wattage,so no the doide you spec'd will only handle 3amps period!
 
Why do you just want to turn on the hatch light? There is a button on the rear dome light that usually melts and needs to be replaced, however the function is to turn off all interior lights to save the battery if you are going to leave your hatch opened for an extended period of time.

Not sure if that is your problem or not, considering you just want the rear dome light to activate.
 
why not just add a small second switch that only allows the cargo light to operate in one setting and both front and rear on the second setting
 
He's replacing the OE cargo light with another unit that has only two wires. In order to retain stock function, he needs the diode to connect the light to the stock wiring. Otherwise, he's got to add additional switches, and won't retain the dimmer knob/jamb switch operation. Plus, sometimes it's just more fun to find a more complex solution and make it work, especially when you can do it in such a way that only someone who knows XJs will be able to tell it's a modification.
 
hubs97xj said:
He's replacing the OE cargo light with another unit that has only two wires. In order to retain stock function, he needs the diode to connect the light to the stock wiring. Otherwise, he's got to add additional switches, and won't retain the dimmer knob/jamb switch operation. Plus, sometimes it's just more fun to find a more complex solution and make it work, especially when you can do it in such a way that only someone who knows XJs will be able to tell it's a modification.
Click to expand...

No he doesn't. He just needs to replace the switch he took out when he removed the 3 wire OEM light.

Terminals of the old light were:
B & C - Common
A - NC Switch in series with lamp to B & C
 
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He's already ruled out using the OEM switches and cargo lights, so yeah, for what he wants to do, he has to modify the existing wiring to work with the lighting he's looking to replace/add.
 
Well honestly I'm not sure what I'll do yet. I bought a $3 toggle at Radio Shack so that I could figure out the cargo light wiring, then hacked a $3 diode into it to see if that would work. The original cargo light is working but the wiring is destroyed on it. I might still use the NAPA lamp, or I might go get another busted OEM one and dress it up pretty now that I know what's up.
 
kennzz05 said:
why not just add a small second switch that only allows the cargo light to operate in one setting and both front and rear on the second setting
Click to expand...

that's a thought. another idea would be to have three positions, ON for the cargo and hatch lights, OFF to kill the cargo entirely, and ON for the interior cabin lights including the cargo light (but not the work light).
 
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