Hot wire- Vixen

[robwells]

By accident I found that the wires from the Light switch get warm when I turn on the Headlights, especially the green and red wire that goes to the fuse box. My local expert has found no wiring or connection fault and concluded I should fit lower rated headlights (currently 2x45a) or fit relays to the main and dip beam wires. What I don't get is, the car was built in 1968, surely it hasn't been running with this problem for the last forty years, there must be a fault. I've spent the best part of eight years carefully rebuilding my Vixen and this problem has resulted in the cancellation of the MOT and subsequent celebrations with the neighbours who are all waiting to see the Vixen on the road. To say I'm disappointed is a understatement. The Vixen is back in the garage with it's dash and steering disconnected and I'm FED UP. Can anyone help please ?

[Grantura MKI]

Have you checked you earth connections?
Best,
D.

[heightswitch]

robwells said:

By accident I found that the wires from the Light switch get warm when I turn on the Headlights, especially the green and red wire that goes to the fuse box. My local expert has found no wiring or connection fault and concluded I should fit lower rated headlights (currently 2x45a) or fit relays to the main and dip beam wires. What I don't get is, the car was built in 1968, surely it hasn't been running with this problem for the last forty years, there must be a fault. I've spent the best part of eight years carefully rebuilding my Vixen and this problem has resulted in the cancellation of the MOT and subsequent celebrations with the neighbours who are all waiting to see the Vixen on the road. To say I'm disappointed is a understatement. The Vixen is back in the garage with it's dash and steering disconnected and I'm FED UP. Can anyone help please ?

Nice to see it getting close Rob. Have you any pics.. If you have upgraded to Halogen from sealed beams then you will be drawing slightly more current.. Earth connections may be the source of the problem.. when you say warm how warm??

Also..Are you using new or the original loom and cable…An original cable may be significantly corroded under the insulation and give a very high current resistance??

N.

Edited by heightswitch on Tuesday 24th June 18:04

Edited by heightswitch on Tuesday 24th June 21:27

[robwells]

Hi Neil, Always nice to hear from you. I would love to finish the Vixen and bring it up to show you. Head lights are 45a sealed beam. I've taken great care with earth connections and they are all sound. Difficult to describe 'warm', but maybe warm like a modem , although hotter at the fuse box. I've used the original loom but all the connections are clean, sound and free of corrosion. To indicate the problem, 3.4amps shows at the light switch when on then rises to 10.3 when head lights are switched on and that's when the cable from the switch to the fuse box starts to heat up.
Have loads of pic's but can't seem to get them on the site. Regards.

[Mr Tiger]

I changed the original spec sealed beam lights for halogens many years ago on my MG Midget. They melted the connectors on the back of the headlight switch. Fitting a relay sorted the problem.

Chris

[heightswitch]

http://www.autosparks.co.uk/product_info.php?produ...

If a worst case scenario.
Drop me a line Rob if you are stuck.


http://www.autosparks.co.uk/index.php?content_page...

Also this will make interesting reading, look at the Lucas guides on cable sizes and continuous ratings…headlamps need more chunky cable so check..It may be a break in part of the cable strands

N.

Edited by heightswitch on Tuesday 24th June 21:15

[Grantura MKI]

Sounds to me that someone has had there mits on your wiring. H-lite circuits do no have a green or red wire involved. Power should be supplied via a brown or solid blue wire with blue with red/white tracers feeding the lites.
Best,
D.

[RCK974X]

2 x 60w at 12 volts = 10 amps, more or less, so that's just about right.

When rebuilding etc, I *ALWAYS* use relays and thicker wire than the original loom, as I reckon the original wires are at best, marginal....even when new....and the switches can also melt more easily when they get older.

I put wires in directly from main battery feed wire, to relays as close to lights as practical, and then have a nice big earth return. Often this makes the headlights noticeably brighter, meaning the original setup was losing watts somewhere, and would have therefore been getting warm.....

The old style bullet connectors can corrode and cause extra resistance too.

Edited by RCK974X on Wednesday 25th June 00:28

[griff 200]

Looks like you are pulling about 7 amps for the headlights looks about right. Surely if you have high resistance. In earth connections or rubber connectors this will make the lights dim and will be increasing the resistance causing less amps to be drawn by the circuit not more???? Sounds like old or wires to small. Properly been like it for years. Richard.

[whitewolf]

When I checked the taimar I was only getting 8.2v at the headlights connections, I didn't notice warm wires bit definatly worth fitting relays (I took the power feed from rear of the alternator (10amp fuse) to relays) and its now giving full power at the lights and brighter.


My problem is/was the original wiring in the bonnet from the car has had its day, strip back the casing and the copper wiring isn't a good looker!

[RCK974X]

griff 200 said:

Looks like you are pulling about 7 amps for the headlights looks about right. Surely if you have high resistance. In earth connections or rubber connectors this will make the lights dim and will be increasing the resistance causing less amps to be drawn by the circuit not more???? Sounds like old or wires to small. Properly been like it for years. Richard.

Just for clarification... Watts = amps X volts, so 2 std 12 volt headlamps at 55w (dip) or 60w (main) should pull 9A dip or 10A main, or very close to that. 7 amps is way too low. (and I agree with Whitewolf)

if the pair 'only' use 7 amps then it indicates there is too much resistance somewhere, which WILL make your wires or switches or connectors warm or hot.

CHECK the voltage directly at the headlight connectors and that will give you a good idea of any voltage drop.

You could also temporarily connect a thick wire directly from battery to the headlamp (CAREFUL!!) and see if headlamp gets brighter...I reckon most older classics WILL get brighter if they have not been rewired

[griff 200]

Sorry did Robert not say he had 45a lamps is this a light code ?? I thought that he had 45amp sealed lights. Is that not 90 watts in total so 7.5 amps at 12 volts???? Did he not say when he turned the lights on he had about 3 volts and up to 10 volts when headlights turned on so about 7 volts to headlights rest to side and tail lights ? A bit difficult not having the meter in you're hand. But relays is always a good way to go especially with old wires and switches.

[RCK974X]

Oops !!

I decided 45a was a TYPE, because a 45 amp headlamp would be 45*12 = 540 watts !! Nice and bright !!

But of course 45 WATTS (90 watts for 2) is indeed 7.5 amps so that all fits neatly.

Sorry about that.....my mistake.

Personally I would rather NOT go with lower power lights, the standard 55/60 sealed beams are already poor on an A road at night, but if most driving is in urban, then no big deal.

But then modern tech. can probably make 45w lights as bright as the old 55w, so perhaps I'm being a dinosaur....

Edited by RCK974X on Thursday 26th June 21:07

[griff 200]

Fair play thanks. Richard