Low beam works but high beam doesnt?

Xcellor

Have a weird problem with headlights, after speaking with a mechanic he thinks its electrical.

All headlights work on dipped but when I engaged full beam the two lights on the right of the car turn off completely. (these bulbs work fine in low beam). The full beam works on the other side... I thought it could be a fuse but since two of the headlights work in full beam I don't see this as likely...

Any ideas?

I am going to try isolate, disconnect one headlight at a time to see if I can eliminate a short circuit ... Any other ideas? Thankfully dont have NCT for ages but still want to get it fixed.

JoeySully

make/model/year would help

Xcellor

JoeySully wrote: »

make/model/year would help

Yes it would

Toyota Avensis 2002 old model.

Some other info... there was no discernable reason for it stopping working. One day they worked, the other day they didnt. I thought it was a bulb problem but I've ruled that out...

Even in low beam the bulbs on the right side of the car seem dimmer...

Avns1s

More likely a bad earth or other bad connection. If it was a short, it's likely be blowing fuses.

Also could be something to do with the relays.

Would really want to do some probing with a multitester.

Xcellor

Avns1s wrote: »

More likely a bad earth or other bad connection. If it was a short, it's likely be blowing fuses.

Also could be something to do with the relays.

Would really want to do some probing with a multitester.

Since I'm in no rush I might take this as a DIY project...

Would I be right in saying the voltage of the right headlights in low beam + full beam should equal that of the left?

Is it likely this is the actual lever on the steering wheel that is the problem. I am inclined to think no since its capable of turning headlights on full beam on one side. But I guess once I eliminate wiring issues I may have to look at this...

I am going to try the following.

1) Disconnect furthest right headlight. Test to see if its neighbour starts to work ok.
2) repeat other way around
3) Clean conenctors with WD40 or some other cleaner.
4) get a voltage reader compare all voltages to see

Haven't done a lot of electrical work I suppose the worst damage I could do by tinkering is blow some fuses?

Wheelnut

Xcellor wrote: »

Have a weird problem with headlights, after speaking with a mechanic he thinks its electrical.

That must be the diagnosis of the century!

I go with the bad earth theory too.

Plug

Are they H4 bulbs in the car? They are two filaments inside them. One for the dipped and one for the main beams. Try put in a new bulb on the side the main beam is not working and give it a try. Some cars go like this when a main beam goes in the bulb. I.E a Fiesta etc.

crosshair1

These are not conventionally wired( as in permanent earths/switched live) to both dim & main, the dim and main are both relay fed lives once main light switch is on, the dim is permanently earthed and the mains are earthed through the light switch, the fuses are on relay supply out to each side so a blown fuse may cause both dip and main loss on one side

drBill

Sounds very like it could be a bad earth on the right hand side.

Try using a multimeter to measure the resistance between the earth terminal of the headlamp bulb connector and the chassis. It should be less than 1 ohm.

Xcellor

Thanks for all the replies. I will try and have a look at this sometime during the week. Want some dry weather first!!

Xcellor

Plug wrote: »

Are they H4 bulbs in the car? They are two filaments inside them. One for the dipped and one for the main beams. Try put in a new bulb on the side the main beam is not working and give it a try. Some cars go like this when a main beam goes in the bulb. I.E a Fiesta etc.

Single filament per bulb

dharn

is that the same car with the oil pressure problems ?

Xcellor

dharn wrote: »

is that the same car with the oil pressure problems ?

Yes but I fixed this head light issue yesterday. Had a poke around in the fuse box and after referring to the manual realised that the right headlights have a seperate fuse. I checked the fuse and sure enough it was gone.

I swapped in a spare fuse and turned on the lights and all is working normally. Light on dashboard behaving normally, full beam on both sides.

I guess the last light bulb that blew must have created a surge which blew the fuse. (15 amp?)

dharn

good one down one to go the joys of motoring