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Help with defroster/lights

S

Spearfisher XJ

NAXJA Forum User
Location
SoCal/Maritime Academy
Well the plans for hooking up my rear light off of my rear defroster on my bumper came to a halt today.

I tested the defroster leads with the key on, and defroster switch off, and it read "continuity". Okay sounds good.

Then, with the key on and defroster switch on, it made a clicking noise from underneath the dash as the switch was applied and would continue to click as long as the switch was depressed. The driver side lead for the defroster jumped between 6V and 12V, vary rapidly and in conjunction with the clicks. The passenger side simply read Continuity.

What's the deal with the click? Can I get it to run a steady 12V the whole way back?
 
For an 87, the defroster grid relay is under the dash. Maybe that has gone bad? It's a funky relay that contains some solid state components and a regular relay. Maybe you can switch it out for a regular relay and rid of the timer and fluctuating voltage. You'll have to control the new relay with a switch that stays "ON" instead of the momentary defogger switch.
 
Why wouldn't I be able to use the existing switch? My understanding was that it turns on, and then the simply turns off after the 10 minute timer? I'm fine with having a timer , actually I would like it. I just need a constant 12V source and I think if I replace that relay with a constant voltage relay it would do the trick?
 
The relay contains the timer etc. hence the solid state components within. The trigger to turn on the defroster is a momentary 12v+ to the relay/timer which then stays on for 10min. If you replace with a regular relay and keep the existing switch, your light will only stay on as long as you keep pressing the switch.

If you want to keep the timer, maybe there is something wrong with your existing defroster relay. I can't imagine why it would bounce between 6 and 12V. I think it may possibly be broken.
 
Yeah that's what I'm thinking. I pulled the switch and it has 4 leads to it, so I will test them and see which ones I actually need. Is the relay look like a standard black relay or is it look like a flasher relay etc?
 
relay_zpse30fae4f.jpg
 
Nope, they don't look like standard relays. They look pretty much like the one you took a picture of. The defroster relay should have two thick 12ga wires going to it. One brown and the other brown with a tracer.
 
Got it wired in. Turned out great.

Just used the to heavy gauge brown wires, and a ground and thats it. Deleted the yellow and blue wires, and deleted the relay. Switch is rated to 20A, have a 10A fuse, and 55w Light.
 
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