Low Beams Dead - Shortly After High Beams Die

Hi there,

I am posting on behalf of my father so some info I dont have. Anyways, i was told he was driving with low beams and both lights went out, he then switched to high beams but after 15 minutes those lights when out as well. He has replaced the high beam relay with no luck.

I will be giving him a list of other things to check but i am wondering if someone has had this same issue and has ideas for items to check. I just found it really weird that the low beams went out so he used high beams to drive but they then went out as well.

Hopefully this issue has come up before!

Cheers all!

Chris,

 

Maybe a loose ground.

 

As far as I know the first gen trucks without DRL use ground switched headlights.

If you pull the headlight connectors off the back of the lights (pull them both at the same time for testing), there should be + power at one terminal only whenever the main headlight switch is twisted to the on position. Moving the dimmer from high to low should not affect the power on that one terminal. One of the remaining two terminals will show ground in the low beam position, the other in high beam.

Again, I am not 100% sure this is the setup on a first gen, my experience with this is on an 86 Toyota truck. On those trucks the common problem is a bad dimmer switch (high/low beam/column switch).

If that switch is your problem, applying ground to either the high or low beam ground terminal at the headlight connector while the main switch is on and positive power is present at the common terminal will make the lights come on.

 

This guy has a good writeup on the headlight system for earlier trucks. I believe it still applies to a first gen. http://www.4crawler.com/4x4/CheapTricks/Headlights.shtml#OnLineOrdering

 

The Truck has DRL.

Where abouts is the DRL fuse located, and the DRL bus bar, is there a way to bypass the DRL system? My dad figures it may be the issue?

 

Also, if there is a module issue somewhere or relay issue, there there any to jumper to get the lows running. Just asking as the truck is needed tomorrow first thing

 

I am wondering if someone has a schematic or knows which wire supplies which at the headlight plug. My dads truck has 3 wires going to each light. Just wondering if you know which wire is for low, high and ground. Its a 98 tacoma 4x4 3.4L

Also, what is this item, its located between the battery and the drivers side fender

 

I found this on AutoZone's website.

 

Not sure what that box is. Is it connected to the headlights?

Knowing it's drl, I'd check every fuse shown on that diagram. If they are okay, my best guess would be a bad DRL relay. (main one with all the wires going into it on the diagram).

If I was you, and I needed the truck right away, I would cut the wires at the headlight plugs, ground the ground wires direct the the fenders, and then run a fused wire from the battery to the low beams. It is not worth the risk of not running a fuse for any reason!

Do you have any switches, relays, connectors available to wire up a bypass? If not, and you can get to an open auto parts store, or possibly a Walmart or something of that nature that would sell auxillary lighting, a basic wiring kit for adding auxillary lights could be modified to get you some lights temporarily. With a little more work it could even be permanent.

 

He apparently has voltage at the headlight plug and he tried putting a wire into the ground of the plug and to the battery with no luck, is there anything that wont let the lights work aside from the bulbs if theres actually voltage at the plug?

 

That's odd. If the bulbs are good, direct voltage should light them up.

I will say that if you test voltage at a connector that is disconnected from any electrical load (light bulb), that voltage measurement can be inaccurate. A bad connection or a bad relay, switch, etc can show voltage until load is applied, then fall to nothing.

Sounds like he's identified the different wires at the headlight. I'd try jumping both ground and power to the appropriate terminals with the headlight connector completely disconnected. If the bulb lights, the problem is in the trucks wiring, relays, etc. (likely)

 

If he does have positive power to either the high or low beam wire at the light, and it's dropping under load, I'd suspect a bad headlight or dimmer relay shown on the diagram.

Those relays are probably in the main fuse box under the hood. I'd expect the headlight high and low fuses are there as well. Usually you can pull relays out of the fuse box and jumper the contacts in the box for testing purposes. Just make sure you are jumping the switch contacts and not the coil contacts. Don't want to fry anything. Usually relay terminals will be numbered. Common numbers for relay coils are 85 and 86. Switching contacts are usually numbered 87, 87a, 30. Often there will be a diagram on the relay itself telling you what terminal does what.

 

Does anyone happen to have a headlight wiring diagram and possibly a diagram of the voltage's a certain electrical components throughout the headlight system?

Cheers,

 

Well, I managed to get up to see my father and it turns out it was just the bulbs!

Although im sure its very rare. Both low beams went out at the same time, he switched to high beams and they ran about 15 minutes before they both went out. So its rare, but happens!

 

voltage checks tell all also voltage under a load tells much more but i have seen headlights do strange things like the regular light circuit inside the bulb burn itself to the high beam circuit causeing strange problems