strange headlight electrical problem

[andycook]

Hi

Headlights on truck doing strange things today, after working fine for last 3 years

The main headlights work fine on dipped beam, but when i push control stick forward for full beam, the lights go off (side lights stay on) AND my 2 sets of SPOTS that only come on with full beam - come on - as expected.
however, they sometimes come after a short while.

BUT If i pull the control stick towards me e.g. like you would to breifly flash headlights, the main beams work fine (along with my spots)

whats going on? Since the spots work fine, it cant be a switch problem
and as for relay problem, why do the work in flashing mode ?

weird

[BUSHWHACKER]

Hi

Headlights on truck doing strange things today, after working fine for last 3 years

The main headlights work fine on dipped beam, but when i push control stick forward for full beam, the lights go off (side lights stay on) AND my 2 sets of SPOTS that only come on with full beam - come on - as expected.
however, they sometimes come after a short while.

BUT If i pull the control stick towards me e.g. like you would to breifly flash headlights, the main beams work fine (along with my spots)

whats going on? Since the spots work fine, it cant be a switch problem
and as for relay problem, why do the work in flashing mode ?

weird

Dirty contacts in the stalk switch, or the contacts have lost their 'springyness' and not coming together firmly.
Used to happen on my Minis .

[Andy Dawson]

Try disconnecting the relay for the spots and checking that your main beam works correctly - if it does then your spots are pulling too much current for the main beam relay.
I know it doesn't make sence, but car electrics rarely do!!!

[andycook]

thanks for replies

Bushwacker: the spots work fine, on both stalk positions - so cant be the contacts!

Andy: I just disconnected the relay for one set of spots, and problem persists..

I first noticed it today, when driving along on full beam and lights suddenly got slightly brighter! - which was the main lights coming on - i hadnt realized they were off!, as the spots were doing a good job of lighting the road.

both sets of spots have independent relays, that are controlled by highbeam feed to headlight - connected just behind headlight

[dave.j.robbo]

Bushwacker: the spots work fine, on both stalk positions - so cant be the contacts!

Could still be. Dirty, high resistance contacts can cause all sorts of problems..

[Andy Dawson]

It hate car electics with a passion - they are a rule unto them selves.

1/ are both spots controled from the same mainbeam wire?
2/ try disconnecting both relays
3/ check the earths are ok (with a meter is best - make sure the reading is the same for both spots)
4/ try changing the Main Beam Relay
5/ hope some one more knowledgable come by to help

[andycook]

OK - i will check the contacts on the control stalks tomorrow,
thanks for help so far

i will also try disconnecting both spot relays and check earths

Yes- both sets of spots relays are controlled by drivers side mainbeam wire

[MattF]

Disconnect any additions and then diagnose. Start with your basic circuit and work upwards.

[andycook]

forgot to mention.... I have a switch for each set of spots, and i turned both these off, so that spot relays are inactive & therefore spots off, and main beam still only works in flashing mode

[Maverick]

I'm suspisious of the main beam switch in the steering wheel stalk, although in theory this should also effect the spots.
Just a thought.

[andycook]

Many thanks for your help peeps!


it turned out to be the contacts on the control stalk,
i dont have a fine file, so used blade of a screwdriver to s$$$$e the contacts to clean them. I will get a file and do a better job in the future,
but have main beam back on headlights now!

why the spots worked fine - who knows! must have been a resistance thing as dave.j.robbo suggested!

anyway, cheers for your help again, much appreciated

[Tallyman]

Could be the extra current pull of the spots was causing the stalk contact to erode. Cleaning them will have restored good connectivity but having had it happen once, keep an eye on them. Might also be helpful to take a separate feed from each headlight to only one spot. Try doing it to opposite sides so that if one feed goes you will still have lights each side of the truck.

[andycook]

Tallyman
the only extra current pull just goes through 2 relay that activate the spots.
the main current for lighting the spots is direct from battery (switched via the relay)

[dave.j.robbo]

the main current for lighting the spots is direct from battery (switched via the relay)

And through a fuse, I hope!

[andycook]

yes - a separate fuse for each set of spots! 20 or 30 amps