Headlights not working

NeilW · Member

Headlights not working

Baz421 · Guru

Follow the wires from a light back to relay is easiest

NeilW · Member

Baz421, is that under the dash somewhere?

Baz421 · Guru

Start at light and follow wire

Cupie · Guru

This link has a manual (soft copy download) for around $14. Should have a circuit that may help.

https://www.tradebit.com/filedetail.php/155673370-mazda-t3000-t3500-t4000-truck-workshop-service

Greg 1 · Guru

More often than not there is a secondary fuse and relay box in the engine compartment as well as the primary one under the dash. Have you check to see if this is the case and if there is an issue in the secondary box?

NeilW · Member

Greg 1, Ill be checking that this morning. After that it means Ill have to strip the huge wiring loom under the dash to follow those wires. Wish me luck.

jebs · Veteran Member

If you go to eBay you can buy a cable tracer (F Set) for about $20-30 makes life easy

Baz421 · Guru

Neil. Follow the power wire, it will be coloured,, from the headlight back to the wiring loom. Then follow the loom and see where the wire COMES OUT OF THE LOOM and follow it. When it comes to the relay, test to see if power at relay, WITH LIGHT SWITCH ON. Wires are colour coded to allow you to do this. Good hunting lol.

dogbox · Guru

have you checked to see if you have power at the switch

Jaahn · Guru

NeilW wrote:
Greg 1, Ill be checking that this morning. After that it means Ill have to strip the huge wiring loom under the dash to follow those wires. Wish me luck.

Hi Greg smile

Do not strip the harness out. That is just more work to fix. It is a simple enough system for the lights just get the colours at the light harness end. Check the earths there too.

What is the history before it failed, that might reveal something. The problems will be at the ends of the wires not in the bunched wires, most likely. The switch, a fuse, a relay, a connector burnt etc.

Jaahn

Aus-Kiwi · Guru

High and low beam ? If not in engine bay . Id be looking under dash . Had one as work vehicle ? Pretty sure its under dash .

-- Edited by Aus-Kiwi on Saturday 14th of September 2019 11:10:22 PM

Jaahn · Guru

Hi Neil smile

Have you checked the obvious things first. Last week I fixed my daughters headlights, low beam not working!! Actually it was only that both globes had blown out so just had to put two new globes in !! Possibly one had blown a while before but not noticed. Do not assume a complicated problem hmm

Jaahn

Cupie · Guru

Jaahn wrote:
Hi Neil
Have you checked the obvious things first. Last week I fixed my daughters headlights, low beam not working!! Actually it was only that both globes had blown out so just had to put two new globes in !! Possibly one had blown a while before but not noticed. Do not assume a complicated problem
Jaahn

I couldn't agree more.

In my days as a Technician, only a half a century or more ago,I would often encounter those who immediately took the 'hi tech' path in looking for a solution when dummies like me just followed a structured approach that checked off those 'common causes', like blown bulbs, early in the process. Yair I know the fuse is one of those common causes.

In this case (after checking the obvious like the bulbs & connections) following the 'halving' principle is the way to go IMHO. eg, The half way in the path is perhaps the horn relay. You might not even have to locate the elusive fuse except for future reference. Of course you should have a wiring diagram et al from the manual.

denmonkey · Senior Member

tracing a harness to track a wire doesn't sound like much fun. plus is may be hard to access etc unless your keen to do the upside down thing under the dash or to get to the back of the fuse block under the bonnet.
Both fuse blocks should have a diagram on the lid/removed panel which should show you which fuse is responsible for what?
Worst case scenario, if you can't find the specific one, just pull one fuse at a time and check them. Wouldn't hurt to check the others anyway.
I'm much prefer to spend 20 minutes pulling and checking every fuse than unwrapping or cutting into a wiring harness, only to have to redo it again.
Don't strip the harness, it's turning a simple enough job into a big pain in the backside job. Plenty of other options to try first.
But as Jaahn said, simple first

On another note, check your tail lights as well. I know the car is older but usually both headlights aren't on the same fuse. They tend to do separate for left and right sides, which means if your left headlight is out, often the rear left tail light goes as well.
This is so when you lose a fuse, you don't lose both headlights at the same time

good luck.

cheers Brett

Aus-Kiwi · Guru

Test lamps !! Could even be a faulty relay or switch . Bad earth ? I have found on older vehicles the relay connection box connector pushes out and when relay seems to be pushed in ? It doesnt push the lugs or pins into connectors !