Headlights only working on full beam after install new headlight AC ACE Bristol

[Simondgb]

Hi everyone,

I have just purchased my first AC Ace Bristol. 2 owner 30k miles from new never been restored.

I have a just broken my new toy to replace a pair of generic sealed beam lights with a beautiful pair of Lucas LeMans with 45w bulb.  After installing the driver’s side light I tested it and it worked. Once I clicked full beam, both stopped working. Now, I the lights only seem to work on full besm only.  I checked the fuses in the little lucas square fuse box and all is ok.  I’m guessing I overloaded a tired relay and it is now bypassing regular beam and only works on full. Any advice would be greatly appreciated.

If it is the relay, i’m not sure which one. There are a couple under the bonnet and one under the dash.

Best Regards,


Simon De Giuli Botta

[Simondgb]

Does anyone have a photo of the headlight relay? Is it the DB10 unit that could be st fault sending power to the high beam bypassing low?

[nicksonsticks]

Hi Simon, I'm guessing you may have done some checks already but if not then it's definately worth proving a few things before replacing anything. It could be the relay at fault but let's prove it before replacing.
Asuming all the lights worked fine before. All you need to get some accurate info is a 12v test light with a proper bulb (21w ideally). Remove both headlights and check the feeds and ground. Blue/red is dip beam, blue /white is main beam. Connect your test light to the battery earth terminal and the other end to the main beam wire and operate main beam,  do the same for dip beam. If the test light operates then it's not the relay. Check the earth wire, connect your test light to the earth wire at the headlight and the other end to the battery, if it lights up then the earth is ok. I'm assuming that one of these tests will show a fault at which point you can follow the appropriate wire back untill you come to a point where the feed goes in but doesn't come out e.g. at the relay or quite likely at a corroded connector etc.
Hope this helps a little bit. Let us know how you get on.
Kind regards Nick

[Simondgb]

Thank you very much for the reply. So, I found out there are 2 issues. One of the bulb holders on the new lights had a bad connection which is now fixed so both lights come on now with high beam. Same for the sealed beams. I will test the connections tomorrow. In any case I have ordered as a spare a DB10 unit. Just in case