mmcpeck

Alright I checked for ground on the relay base, and it looks like there is ground being supplied from the switch to the side of the relay with the small slots. But when I put a meter between the small slots, with the switch on, I only get like 3.5V.

Now one side of the small slots has 12V all the time, and I can measure that when I put the meter between the Negative side of the battery and the constant 12V small slot. But when I turn the switch on, I only get the 3.5V from that same slot.

Is this a bad ground or is that all it takes to energize the relay in order for it to connect the 12V through to the headlights?

4Crawler

iTrader: (3)

Probably dirty contact in the combo switch or a bad connection between the relay socket and that switch:
- http://www.4crawler.com/4x4/CheapTri...eadlight_Combo

mmcpeck

So I should be seeing more than 3.5V through the small slots on the relay socket, with the headlight switch on?

I take it 12V is what is needed to energize the relay and then pass the 12V from the larger slots in the socket through the relay and to the headlights?

Does the switch in a '91 supply grounds to headlights too, or just supply ground to the relay? I don't see how "jumping" the relay with a piece of wire would work with the switch off, if the headlights didn't have a separate ground.

Thanks.

4Crawler

iTrader: (3)

A 12v relay usually needs anywhere from 6-9 volts across the coil to turn on and pull ion the contacts. 3.5 volts will not cut it. And when the contacts close the 12 volts at one contact is send to the other contact and that goes off to the common terminal of the head light bulbs (bulbs have 3 terminals, low beam, high beam and a common connection where high and low are tied together). The headlight/combo switch ground out the relay coil to turn it on to supply 12 volts to the headlights. The combo switch also then grounds out the low or high beam filaments to turn them on or in flash mode (pull back on the dimmer switch) both high and low beams are grounded and both turn on.

Only exception to the above is if you have the daytime running lights in which case you have a more common switched power setup.

Why would jumping the relay work with the switch off? Well, you might have a short to ground some place in the headlight wiring that causes the headlights to come on. Look at the wiring diagram above, the headlights should not come on with simply power applied as they should have no ground connection and you need both to complete the circuit and have current flow.

scrossDC

hey im new and i dont know if you figured ur problem out yet but wheni bought my 93 last week had the same problem everything worked but the headlights and once in awhile the brights would work.. it turned out to be the switch no fuses no relays got a switch from a junkyard and the lights work fine.

mmcpeck

Thanks scrossDC......how did you test the switch to find out it was the problem?

4Crawler laid out some nice procedures that I am gonna go by, but figured I'd see what you did.

Gonna hook my relay up to 12V with alligator clips from the battery, to see if I can hear it energize (click), then I can at least know if the relay is good or bad.

scrossDC

pulled the steering wheel and pulled the switch off then plugged the assembly into a friends exact truck where there were no problems. its easy to check if you know someone else with a yota

mmcpeck

Yup that's what I was gonna do, pull the switch like 4Crawler suggested.

mmcpeck

OK, so I am totally confused now. I pulled the relay and hooked it to 12V at the battery with some alligator clips, and it clicked like it should, closing the contacts.

Next I hooked up a meter to the other side of the relay, and connected 12v again and the meter showed conductivity through the relay, well it showed .006 ohms through it when the relay was energized, so I figure the relay is good, right?.

I checked for ground at the small slots of the relay socket and with the headlight switch turned on, I get 11.75v, meaning the switch is providing ground to the socket and realy, and 11.75v should be enough to energize the relay right?

When I plug the relay back in and turn the switch on the relay does NOT click and energize.

So how could it energize when I connect it directly to the battery, but not when it gets 11.75v when the switch is turned on????

Is this a bad relay? Should I be seeing less than .006 ohms when the relay is energized.

This is making me crazy!! You don't realize how much you need headlights until you don't have them. It gets dark at like 4:30 now, and I've gotten stuck at work like 3 times.

4Crawler

iTrader: (3)

Well, one possibility is that you are measuring the relay socket voltage under a no-load condition (i.e. the relay pulled out) and also testing it in a bench condition (i.e. applying 12 volts to it's coil) and both those test fine. What you are not testing is a loaded voltage at the socket with the relay installed. Since you see only 11.75 volts at the socket under no load, that is suspicious, you should see the full battery voltage there under no-load. That would point to there being some high resistance in the headlight switch-relay wiring. I suspect that with the relay plugged in, you would see that same 11.75 volt reading to drop to leas than half that value, low enough to cause the relay coil not to energize and pull in the contacts.

mmcpeck

Thanks 4 Crawler. I figured the 11.75v I was seeing was do to the fact that the parking light and rear lights were on when the switch is turned on, so I figured this drain was what was giving me the lower voltage.

When I have the switch on and I measure the voltage in the bigger socket slot (the side that passes through to the headlights when the relay is energized) I get around 11.9v, I figured that was due to the other lights being on. I know those voltages are low to begin with, my battery may be on it's way out, maybe I should measure these with the engine running?

Anyway thanks for the help. From what I have told you, do you think this is the relay at all, since it energized and had .06 ohms when energized?

Thanks.

4Crawler

iTrader: (3)

From your tests, the relay looks good. It turns on and off when 12 volts is applied to the coil and the contacts close and seem to make good electrical contact. However, the best relay in the world will not work if it is not given sufficient voltage to turn on. Kind of like an engine that is out of gas, sure the engine won't run, but that is a symptom of the problem (i.e. no gas in the tank) and not the problem itself.

mmcpeck

How can I test the relay socket for correct voltage with it under load?

mmcpeck

OK, it's been a while since I last posted about this problem, it's been freezing out and I have been busy, so basically just sucking up having no headlights.

Anyway I started messing around with it again and when I jump the relay socket with a jumper wire, my headlights will turn on, even with the combo switch not turned on. Someone earlier had mentioned that this should not happen, since the combo switch also applies the ground to the headlights themselves, when turned on.

Is that true? I don't see what the purpose would be of having the switch supply ground to both the relay and the headlights.

Anyway, when I do jump the relay socket with a jumper wire, the lights turn on and the high beams will work by either pulling on or pushing the turn signal lever...as usual.

But the highbeams won't flash at all when I don't have the relay socket jumped. Meaning not only do the headlights not turn, but I can't even flash the beams.....unless of course I jump the relay socket.

So if I expalined this well enough for you guys to understand, does this sound like a bad combo switch? I get that turning the switch provides ground to the relay so it will energize and pass 12V through to the headlights, but would that part of the switch being broken also keep me from being able to flash my highbeams?

I may be starting to confuse myself, but it just seems to me that if I can flash my highbeams when I jump the relay socket, then they should still flash when I don't have it jumped, even though my headlights won't turn on, right??? The same as if everything is working fine, how you can flash your lights even without your headlights turned on.

So whatever the problem is, it is keeping me from both turning my lights on with the switch and also flashing my high beams with the switch turned off.

I don't know, this is driving me crazy. One day they worked and the next they just didn't. No flashing on or off with bumps, like I've seen mentioned, no high beams having intermittant problems, like I've seen mentioned....just nothing.

Also, what is the procedure for pulling the steering wheel on a '91 4Runner? I may just pull the switch out and see if I can test it somehow.

Thanks for any help.

4Crawler

iTrader: (3)

Turning the combo switch knob turns on the headlight relay to supply power to the headlights. Then the lever of the combo switch grounds one or both of the high and low beam filaments to complete the circuit to turn on the head lights. So in normal low beam position, the lever setting gives the low beams a path to ground, jumping the relay supplies power. Power + light bulb + ground is a complete circuit, let there be light!


Well could be one of two things, perhaps something is causing the relay to turn off when in highbeam or flash position. To test this, have someone flip between low and high while you touch the headlight relay and feel if it is clicking on and off (it should just stay on all the time). If the relay is clicking on and off as you flip low/high, then figure out why, either the switch is flaking out or there is a wiring issue, perhaps a loose connection that pulls loose when you move the lever or something.

desconhecido

See this diagram:http://www.ncttora.com/fsm/1990-1995...i/hdlitusa.pdf

You can see from this diagram that either the high beams or low beams (or both) have a circuit to ground through the combo switch at all times. So, when you jumper between #4 and #5 in the relay socket, one or both sets of lights should have a complete power circuit and should turn on. This is a good thing and it tells you that the ground through the combo switch is being made.

There are two ways that you should be able to close the relay: 1. by turning on the headlight switch and 2. by activating the "flash." Either of these should provide a ground to #3 on the relay, thereby closing the relay and completing the headlight power circuit. Have you tried "flashing" with the relay installed?

mmcpeck

Thanks 4Crawler!!!

I now understand how it works. The lever sitting in normal (low beam) position is always supplying ground to the headlight low beam circuit, so when I jump the relay socket it doesn't matter if the switch it turned on or not, since the ground is still there from the lever position.

When I do jump the relay circuit, my high beams work whether I pull the lever back into "flash" position or whether I push it forward to the constant high beam setting. But the "flash" will not work at all unless I have the relay socket jumped, and the "flash" should work whether the headlights are on or not.

So it makes sense that in order for the constant high beam setting to work, there has to be 12v supplied to the headlights, via the combo switch being turned on, hence supplying ground to the relay, closing it and sending 12v to the headlights, since you would only need constant high beams while driving at night....OK fine.

But since the "flash" position should work even when the headlights are off, it seems like pulling back on the lever to the flash position, will/should supply both ground to the relay and ground to the high beam circuit when the headlight switch is off...say if you were just flashing someone during the daytime.

In which case the flash position would have to supply ground to the relay, the same as turning the combo switch on would do. And I would assume that this would be through the same wire/circuit for both.

So it's possible that I either have a bad connection in the switch to that ground wire, or a bad conection somewhere on that ground wire...or possibly the connection to this ground circuit is just shot inside of the combo switch....meaning I would need a new combo switch.

Does this sound correct? I hope so.

I think I will pull the steering wheel and go get myself a junkyard combo switch.

Any tips on the easiest way to pull the steering wheel off.

Also who were the guys on here that sell used parts? I'd rather order one from somebody than go to a junkyard and sift around in 15 degree weather.

Thanks for all the help....once again this board is priceless!!!

mmcpeck

Hey desconhecido. I have tried using the "flash" with the relay installed, and I get nothing, but the flash works when I jump the relay socket...#4 and #5 as you said, which makes sense.

I completely understand what you are saying. So the lever of my combo switch seems to be grounding low beams and high beams, but it looks like my combo switch is not providing the ground to the relay...either through turning the switch on or through the flash feature.

Am I corrrect in assuming that the "flash" feature should supply ground to both the relay as well as the high beam circuit?

And if that is correct, then can I assume that it is the same ground circuit to the relay whether you twist the switch or pull back on the flash?

If so, it seems my switch is bad.

Thanks.

desconhecido

Yeah, the flash supplies ground to both the relay and to the high beam circuit. But, it looks like there are actually two separate grounding circuits in the combo switch. One for the flash and one for the head light switch. So, it sounds like it's probably the combo switch that's at fault, but it seems odd that both circuits would fail suddenly like that.

4crawler has some good stuff about combo switch repair on his website:http://www.4crawler.com/4x4/CheapTri...eadlight_Combo

mmcpeck

Alright thanks guys.

I think I am looking at a bad switch. I wil pull it and go through 4Crawler's steps, just to see what it looks like.

This looks to be an original switch, and the truck has 200K on it, so I guess I can't be too surprised that it has a problem.....if it is the problem.