Bad Earth Or Blown Fuse?

[baz1631]

Hello again , more problems! I've got a dodgy light (front n/s) and dont know wots wrong , and would like some help/advice on how to fix.......

Cant get much power on dipped beam (looks like brown light instead of white) and goes even dimmer on full beam.Ive checked fuses that I can see and none are blown (are there any hidden ones?) and tried the earth points on the side of the bodywork next to unit, also earth points in the n/s kick panel, to no avail abd all are tight and clean. Can any body help?

[Tech01]

Amost certainly the earth connection to the n/s headlamp bulb has become disconnected. Suggest you unplug the connector from the headlamp bulb, and identify which two of the three connections are Supply (use a voltmeter or testlamp - one pin should go +12v on main beam setting, and the other +12v on dipped). The third connection should be permanent earth. If it isn't earthing properly, try running a temporary connection between this pin and chassis, and see if this cures the problem. If it does cure it, make this temporary connection into a permanent one.

Absence of a ground connection at the headlamp bulb will make the two lamp filaments run in series, and possibly series again back through one of the filaments on the other headlamp bulb before reaching earth. Guaranteed to make the lamp look dim!

Good luck,

Chris

[baz1631]

Hi tech01, thanks for the reply. tried wot u said and lights wre coming on without switch!. also tried direct lead to +terminal on bat. f rom live lead on connector and...bingo! lights all work as they should ie: dipped/main beam come on when switched on!. Would a faulty or worn connection/wire cause the same problem? 'cause it seems to have cured the fault.! Hope I havent done anything stupid!!!!

[Tech01]

Hi Baz,

My original reply was done without looking at the wiring diagram - sorry for this. I've just checked the Toyota diagram for RHD headlights, and

1 The supply to each headlight is via a 10A fuse (look for H-LP LH, and H-LP RH in your owner's book), and this is taken, effectively, straight from the Battery. That means that each headlight "common" terminal (the one which I originally assumed was a ground connection) is receiving a "permanently live" feed.

2 The dipped beam is switched on by the steering column light switch ('Combination Switch') making a connection to earth/chassis. According to my diagram, a White-Black lead leaves the switch, and goes to chassis at an earthing point "on the Right Hand kick panel".

3 It appears that this earthing point is for the purposes of activating the headlights only. Other lights (side, tail, numberplate, fog, etc) get a +12 live supply from the Combination Switch, which then goes to the relevant lamp, and then to ground.

So, if your sidelights etc all work OK, but the headlights don't, I'd suspect either the earthing point in #2 above, or a defective Combination switch, or (most likely) and poor connection along this route.

Hope helpful,

Chris

PS Not sure what year your RAV is; let me know if you reply.

[baz1631]

hi tech01, thanx again for the quick reply, yes the side/dipped and main beam all come on as they should. I was won dering why the lights worked all right when connected to Battery! and after reading your post I UNDERSTAND! I'll wire it up all properly ( was only done as a quick fix/temporary till I got home after nightshift!)Your reply has renewd my faith in mechanics ! and given me a wee confidence boost! thanx again and keep on ravin'! PS: my car is a 02 plate rav d4d 5door..........much to BIG KEV'S disgust ! n (he dose'nt like 5 doors on a car for some reason) ha ha ha