I’m returning to my headlights again to sort a few issues and hopefully get them sorted for an mot. All was well and then first one sidelight bulb and then the other went out. Deciding enough was enough I pulled the cover back over it and after a 3 month spell on night shift it’s now time to get things sorted. I’m sure the outer sidelights should come on first but can’t remember the exact order the switch operates in. All I’m getting at the moment is all 4 main headlights on. I’m going to start investigating tomorrow. 1. Can anyone tell me the order of play that the lights should work in from the switch.( I have no fog lights fitted don’t know if this affects anything?) 2. Which fuses should I check? Are they in the box attached to the wing and I’ve read Greg recommends uprating them but to what size? 3. What if any bulb upgrades would you do? I’ve seen examples of led but not sure on those.4. Anything else you think might be of help? I’m not very good with electrics so any help as always is very much appreciated

 

Brinny
First click is the sidelights, back and front. Check if the rears come on, if they do the switch should be OK.

The sidelight fuses are in the auxiliary fuse box under the passenger side shin trim which has to be removed to get at it. Fuse nos 14 LHS and 15 RHS, one for each side.

If all good, remove one of the outer headlights, the sidelight bulb holder will probably be a push fit into the headlight unit, just below the main bulb. Check that the bulbs are good, or even replace anyway.
With a test light: and the sidelights switched on check if there is 12 volts at the centre part of the bulb holder (the clip going to a known good earth) and if the bulb holder earth (the metal part of the holder body) earths properly (indicated by the bulb in the test unit lighting up). If no 12 volts and a good earth, then the problem is elsewhere.
There are no relays in the circuits, but they do go through bulb failure units. Does your bulb failure unit stay on after about a minute? The panel lights and gerabox selector lights should come on with the sidelights, by the way, do they?

 

Thanks for that Greg I will have a look tomorrow. Very helpful. Will report back.

 

I have these LED H4 bulbs in my outer lights and the H1 LED bulbs in the inner lights
Quicksilver Automotive (bettercarlighting.co.uk)

 

How do they perform?

 

thankyou for the help. Bit too pricey for me, though I’m sure there worth it.

 

checked everything greg. Rear lights on ok. Panel and gear selector lights on ok. All fuses ok. Bulbs ok. Bulb failure light staying on. No 12 v at side lights? Could it be the big silver thing on the inner wing? All was good then they failed one after the other? They were installed by a proper auto electrician.

 

What big silver thing?

Next thing to test for is if there are 12v at the bulb failure warning unit. For the front sidelights this is located, as the auxiliary fuse box, under the passenger shin trim.
It is the lowest module mounted on the shield-shaped piece of steel mounted to the left of the oblong steel plate the aux fuse box it on.
My manual says that there should be 12v at red/slate wire from the switch at this unit, sidelights on. The manual also says that both terminals B and L of this should have 12v sidelights on; these are the terminal having the input from the switch and the output from the unit to the sidelights. If you have 12v coming from thr switch and none going out to the sidelights, bypass the unit and connect the red/brown and red/slate wires, and if there is 12v at the red/slate and the rest of the loom is good, the sidelights should come on.

Bottom unit in this photo
The fact that both lights failed almost at once, could point to a faulty unit. I await reports!

 

Did you have to do any mods to the headlight buckets to accommodate these bulbs?
Jon

 

No they are direct replacement

 

Ive not done any more investigating but wonder if my relay is playing up? Is there any way to test it? Could I check for 12v with the switch on ?

 

Brinny
I think you would be better advised to follow the circuit logically, and test if the bulb failure unit is the problem as in my most recent post
Where does that relay come from? According to my manual there is no relay in the sidelight circuit. Your car may be different, but that does not look like a normal relay, which is all the sidelight circuit would need.

 

Hi Greg, this is the headlamp relay on my car. It takes wires to all the bulbs from it I think. My car is an 89. I seem to recall the auto electrician saying he thought this might have been causing problems before he got everything working. Mine doesn’t look as nice as the one in the photo. I will have a good look at the weekend and use your guidance . Thanks.

 

The headlamp relay is not part of the sidelight circuit, Brinny. Good luck when hunting bat the w/e.

 

Hi Greg, I’ve followed your advice and had a look at this again today. Anyway , I found the items you mentioned and did a test. I had 12v at both the slate wire and the one next to it. I then put a jumper between them but got nothing at the bulb end. ? The bulb failure light is coming on and then going off . Had a look at the wiring but didn’t unwrap any connections . Not sure what to check next. All the other headlights work ok.

 

Brinny,
I think that you are saying:

1. you have found the wire with 12v on it (if all three are disconnected there will only be one with 12v) which is the one from the switch when sidelights switched on
2. That then you connected this wire with 12v on it to at least one if not both, of the other two wires, (warning unit completely bypassed)
3. and no sidelight came on, switch on to sidelights?

According to the wiring diagram I have (copy attached) these two should go directly to the sidelights via the fuses you checked, fuses 14 and 15 in the auxiliary fuse box.

Therefore, assuming I have it right about what you have found, the next test is on the two wires that go to the sidelights from the failure unit. (red/brown I think they are, that is the two wires that do not carry 12v when disconnected from the 12v wire from the switch). The next point they go to is the fuse, so check again that they do provide 12v to the fuses. To do this, remove the fuses, and check that, switch off, there is NO current at the input side of the fuse holder, and that there IS 12v at this side when the lights are switched on.

If all good, the bridge first one fuse holder, switch on the sidelights and see if they come on. Just bridge quickly, with a helper looking at a sidelight while you do it, and unbridge ASAP. Then do the other. If they do come on then:

Replace the fuses with new ones (they can look good but not be) and ensure that the copper clips the fuses go into are tight on the fuses. If they are not, wedge a tiny morsel of rubber down the outside of the copper clip, between it and the plastic divider to tighten it. A bit of wire insulation stripped off the copper wire will do it, for example, pushed in with a tiny screwdriver or similar.

If alternatively, even with the fuse bridged, there is no sidelight, then test for 12v at the lamp socket, fuse bridged, and report back.
What you are doing in all this is verifying each segment of the circuit until we find out where the "blockage" of the 12v feed is. The headlight circuit is nothing, repeat nothing, to do with the sidelight circuit, apart from using the same switch.

 

Cheers Greg. Will try again tomorrow and report back.

 

This is your 89 which should have blade style fuses, rather than glass ones, correct? They are not as likely to give problems, but can still cause issues. Usually, simply unplugging them and plugging them back in will cure any contact issues. Use some electrical contact cleaner on the contacts.

I went thru this exact problem on my 85 yesterday. In my case, it was a glass fuse contact issue. The right front side marker and the right parking light were the ones affected. I pulled both bulbs first, verified that I had good grounds, and that I didn't have 12v at the sockets. Under the dash, I found I had 12v at one side of the fuse contacts, but not the other. Cleaning the contacts with sandpaper and using Deoxit on them solved the issue.

 

thankyou for your help. I am hoping it is a fuse problem as you and Greg have indicated. Not being electrically minded all help is greatly appreciated. I will try again tomorrow after I’ve taken my 3 year old grandson for breakfast with Santa. Many thanks to you both.

 

Brinny
Do you have blade fuses? If so the advice does not change, but I am assuming the aux fuse box has them in the same position as in the manual. The wire colours are the way to check for sure, just make sure they are the same as those coming from the failure unit.