My tractor lamps I have on the rear quit on me.
Yesterday as Todd was following me up the highway to Greenwater I switched on for his to see how bright they were.

I asked on the CB and he said when are you going to turn them on

So, I guess something happened.
The switch lights up, the fuse is good that goes from the battery to the 30 amp relay.

I have a multimeter that I can hook upto the wire that comes off the relay and goes back to the lights.

The problem is I have not used this thing since '96, and I forget how to use it, and I don't have the instructions.

I take it you use the left side of the meter since it has the V=== symbol, and that means direct current, and the right side of the meter that has the V~ symbol means alternating current as in for house wiring?

So what setting, would I use the 20 that is right below and to the right of the V=== symbol?
When you don't work with this stuff all the time, you tend to forget

So if I hook the red poker to the wire coming off the relay that goes back to the lights and the black one to ground, and then throw the switch, I should see 12v.
If I do, then it's the red wire that goes back to my lamps that may be cut somewhere along it's path, or it may have come off back by the lights where it ties into them.

No ground wire back there, the studs for the lamp brackets are the ground, and they are bolted tight to the hitch receiver.

Other than that, the wires on the relay all look good.
I'll have to wait until we get better weather later this week though, as we have been in & out or rain showers here most of the day.

Thanks,

 

You have it figured out correctly Corey.

The === is DC (like on the truck) and the ~~~ is AC, like in the house.

To measure voltage on the truck, set the selector to the "20" position on the DC side. Then take the black probe and attach it to the chassis (with aligator clips or just pin it against a metal piece) and touch the red probe to the output of the relay. When you hit the switch you should see a reading of appx 12v. This could be 11.8 if there's a load on the battery and the engine's not running, or up to 13.8 (maybe a bit more) if the engine's running. The higher voltage comes from the output of the alternator.

If you get nothing, then be sure of the connections (possibly a flakey ground). If still nothing, then look at the other side of the relay - the input side. Make sure that you have a good voltage feed into it. Also be sure that you're getting the trigger voltage to the relay from the switch.

If you have a good voltage feeding the relay, and the trigger voltage is there, then the relay has gone south. Actually, you should be able to hear (or even feel) the relay engage when you hit the switch.


I don't want to over-babble now, but I'll be happy to put up more detail if you need it.


Good luck!

Mark

 

I would check the ground at the lights. Since the ground is exposed to the elements(rain , snow, salt) it will rust out and cause a ground fault. With aux lights i always run a ground wire to a non exposed area like engine compartment. That way it will never rust.

 

OK, here is what I did.
http://www.toyotaoffroad.net/tando/t...lamp_relay.jpg

As you can see by the photo, I have 12.20 v constant from the fused red wire from the battery that feeds the relay, so the fuse is good.

When the switch is flipped, the yellow wire that goes to the relay to energize it also shows 12.20 v at the wire clip.

That in turn should make the other red wire that goes from the relay back to the lamps themselves show voltage.
I am reading zero on the meter.

The relay does click when I flip the switch.
I did wash under the hood two Saturdays ago to get pine needles out of the lip that is right above the relays.
Is it possible to burn out half of the relay?

Zedex, the bolts I am using to attach the lamps to the hitch receiver are the ground for the lamp, and they are stainless steel, as the ones that came with the lamps were to short to go all the way through.

So the ground is good back there.
It looks like the problem is at the relay itself since the red wire that feeds the lamps is showing zero voltage.

That is a good idea though about the seperate ground wire.

The ground on the relay is that black one that goes to the left towards the other relay.
It's screwed right to the firewall, and that relay next to it is also grounded at the same spot.

So I'm guessing here that half of my relay is shorted out?

 

yup.. Its the relay..

 

Hmmm, that will be easy to fix.

Just for the fun of it, I rehooked the meter back up.
Red probe to the red hot fused wire, and the black probe to the black ground on the relay.

Bingo...12.20 v, so the ground for the relay is good taht screws to the firewall.

I bet I toasted the relay when I sprayed the pine needles awhile back?
You know, every once in awhile my roof lights quit too.
But then they come on after a bit.

It must have water in it's relay?
I wonder if you can get water proof relays?
These are just the standard Hella 30 amp ones they include with the Hella 500 lamps.

 

I agree to replace the relay... BUT!

Keep in mind that _something_ burned it out. If you could see inside it, I would bet that you would see that the contacts are fried. This usually comes from too much current (which will generate too much heat which will melt the contacts).

Since you can hear/feel the relay work, then that says that the relay coil itself is fine.

So, before you just swap out the relay, it would be beneficial to figure out just what caused the relay to go. What wattage are those lamps? You have two, right? If that relay is the typical 30 amp model, then that's only 360 watts (at 12v). That means that if those lamps are any mroe than 180 watts each, then you're drawing too much current through the relay.

I don't know how long you've had those there, but it's understandable that something like this could work "fine" for many years and finally just give out.

You may want to ("have" to) move up to a larger relay, or run two, one for each lamp.

 

Yea. I dunno if your supposed to get those relays wet. Probably not. But they are real cheap . You could use a solenoid instead. Alot more durable.

 

I just called Shuck's Auto, and they are $5 each for the 12v 30 amp model.

Mark, my lamps are only 55 w each, so that is 110 w on each relay.
They have been uder the hood for a few years, and they do get sprayed with Gunk Foamy Engine Brite, then hosed off about 6 times a year.

I suppose that could have contributed?

Mine are wired up like this.
https://www.yotatech.com/~corey/tech..._lamp_scan.jpg

Except where they tap into the headlight circuit for the switch to energize the relay, I have my switch setup so I can run the lamps anytime with the key on or off by 12 v constant.

All 3 sets of my lamps are wired up to come on at will.

 

'k.. it sounds like they finally just gave up on ya' then.

 

Yeah bummer...
Oh well, I'll pick up two tomorrow.

That should last a few more years, and I think I will cover these the next time I wash under there.

Thanks a lot for the help guy's.
It was fun diagnosing it with the multimeter instead of guessing what was wrong.

I could have used the backups yesterday coming home on 410.
Todd was in front of me, and I had a white 2WD Toyota truck riding my rear for awhle.
I mean he was right on me.

He went around me and cut in front of me and got on Todd's butt for awhile until he passed him.

 

All fixed!
Picked up two new 30 amp relays.

One thing, you really have to study the instructions with these as not all 12v 30 amp relays are the same.
On the new ones I bought, the energizer wire that comes from my in cab switch and the ground wire on the new relay are switched opposite compared to the old relay I took off.

Other than that, the red fused power wire and the wire that goes back to the lights are in the same position.

Flipped the switch and the rear lights came on the first try.
I like it when things work the first time you flip the switch.