I have a set of 6" KC Slimlites on my truck that I just realized today weren't working. Narrowed it down to the relay switch was bad so I went out and replaced it. I went down to the local Checkers and unfortunately they didn't have the exact replacement switch that I would get from KC if I ordered it online, but they did have a relay switch that match it. I went out and plugged it in and now I have another issue. When I plug the switch in one light will light up even though the toggle switch inside the truck is off. If I turn the toggle switch on then the one light goes out and the other light comes on.

I'm no electrician so I'm looking for a little assistance from anyone who may be or who may know what I problem may be. Thanks

 

can you atleast draw out how it is all supposed to be wired up?

sounds like you have a problem with your switch side of the circuit, or the relay isnt hooked up right....

 

After waaay too many years of experience, let me tell you what a very wise Service Manger once taught me a long time ago. "All stupid / weird electrical problems are a bad ground." He's been proven correct more times than I care to count.

So, what's your problem? First, you said you traced it to a "bad relay switch." I'll take it that it was the switch, not the relay that you replaced since the switch and the relay are separate items. Is it a lighted switch? If so, there are three connections there and one is a ground. Did you hook the new switch up with the correct wires to the correct terminals? Swapping the ground around here by mistake can lead to interesting problems. You also mentioned that only one light comes on. Do both lights actually work if you run a jumper wire? You might have a bad light (or ground) at that end of the circuit too.

I'd verify that the lights actually work (using jumper wires to the battery) first, then go back and look at that switch you replaced.

 

yes he said one is on all the time, he flips the switch and the other original one goes off, and the other one comes on

 

Until we get verification, it sounds like he replaced the relay, and put in a 5 pin relay ( both Normally closed and normally open contacts ) in place of a 4 pin.

Don't ask me how this would be, the harness to the lights I would say would only have 1 set of connections to the relay.

let us know which you replaced, the switch for the relay, or the relay itself ?

simple aux lights wiring diagram :
https://www.f150online.com/galleries...028-188033.jpg

 

Alright here's some pictures I took today.

Light Switch Off


Light Switch On


The new relay switch next to the old relay switch


Another

 

Cont..

Wiring


Fuse


I noticed one difference in the switches today. On each switch there is a diagram and each diagram contains the following numbers;

85, 86, 87, 87 and 30

The difference is on the new switch one of the 87's actually has an "a" (without quotation marks of course) next to it so it's actually 87a. Here's a drawing of the diagram from each switch



Could that be my problem? Should I just return the new switch back to checkers and just order the on directly form KC?

Continued thanks to all for the assistance.

 

There you go, the KC one shows 2 pin 87's, and the standard Bosch relay is 87 & 87A.



Don't know why KC made a relay like that, but one of the lamps is tied to the Normally closed contact ( 87a ) on the one from the Auto parts store. That is why it is on, when the relay is turned off.

2 options, change the harness to splice the wire together for the 87s, so the 87a ( center pin ) is not used, or order the correct KC relay.
Got to hand it to KC, they got you by the short hairs when they do this. Don't think you are going to find that type relay anywhere else.

Standard Relay pin out:

 

Appreciate the assistance and I will just order the correct one from KC. Really was hoping that's all it was and I didn't have to go digging around looking for a bad wire. I truly am no electrician and don't know an amp from an ohm. :o

 

you dont need to order a new one, just chop off the two ends that go into the 87 and 87a, and combing both of those wires and plug them into 87.

You now have a standard ISO relay, and before you had just a relay.
-Patrick

 

Thanks for the heads up on this, but I already went ahead and ordered the correct switch. I may keep this in mind though the next time the switch goes bad. I would think though that after only 8 months the initial switch wouldn't have gone bad, but's that's how long the lights have been on my truck.

 

depends on where you have the relay mounted... Heat, moisture, vibrations, all will weaken the life of the relay

 

Got the new switch in the mail, plugged it in and the lights work perfectly. Hopefully this isn't going to have to be an every 6 month purchase to keep them working.