headlight issue....... help please

[BOYER73S]

Problem with headlights on my 1972 ST build.

They both used to work but both headlights no longer do.

Parking lights both work
High beams work.
Both bulbs have been replaced but no joy.
Fuses replaced but no joy.

As parkers work I assume headlight switch is OK but that may be incorrect.

Thoughts on what to check next please and I am no auto electrician but it surely must be something simple.

Thanks in anticipation.

[gerakroo]

Clyde, you should check your headlight relay. That may be the problem.Its located next to the flasher relay, behind the gauges. Just swap it with the one for your horn relay (next to fusebox) and see if that helps.

[BOYER73S]

Thanks Gerard will do tomorrow and report back

[John912]

If it's the relay, you might want to consider removing the old electro-mechanical innerds and replacing it with a Bosch solid state relay, they fit inside the original metal housing.

https://www.summitracing.com/parts/b...MaAhgwEALw_wcB

[BOYER73S]

Unfortunately the headlight relay runs the horn and the working horn relay does not get the headlights going so I guess we can exclude the relay as the issue.

As an aside when the headlight switch is pulled out to stage one the light in the instruments comes on as it should and when pulled completely on for the headlights the blue light is visible.

Next suggestions please

[edmayo]

The headlight relay sends power to the high beams, then when current is supplied to term. 86 of the relay, from term. 57 of the headlight switch it switches the relay to close the points and send power from term. 87 of the relay to the fuse #3 (yellow wire) and then out fuse #3 and 4 to the low beams. And term 85 of the relay MUST be grounded. If you ran a jumper wire from a power source to term 87 of the relay socket it should operate the low beams if the rest of the circuit from the fuse box to lights is good. Have you done ANY work on the car after which the low beam stopped working.

[BOYER73S]

Thanks Ed

If I read correctly it is still possible the relay is not functioning fully correctly if the high beams do work despite the sand relay firing up the horn when I did what Gerard suggested I check

I will follow your advice re running power to terminal 87 of the relay and sed what happens



I will follow your advice

The headlight relay sends power to the high beams, then when current is supplied to term. 86 of the relay, from term. 57 of the headlight switch it switches the relay to close the points and send power from term. 87 of the relay to the fuse #3 (yellow wire) and then out fuse #3 and 4 to the low beams. And term 85 of the relay MUST be grounded. If you ran a jumper wire from a power source to term 87 of the relay socket it should operate the low beams if the rest of the circuit from the fuse box to lights is good. Have you done ANY work on the car after which the low beam stopped working.

[dirk07]

I guess your headlight switch in the turnsignal stalk is brocken. There is a small Pin inside that caused this problem most of the times I had a headlight problem.

[BOYER73S]

Thanks Dirk

the turn signal stalk only controls high beam on and off and high beam is working fine its just std lights I do not have for some reason.

[HughH]

clyde
did you test if the pull out light switch on the dash is working correctly