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MG MGB Technical - Bad headlamp switches
|Has anyone had experience with new headlamp switches burning out? I've replaced two new switches recently in 72-76 MGBs. Both had been replaced ( I'm assuming because they looked bad but, were working switches ) and the new ones melted in the back where the wires connect. I don't know who the supplier was in either case. These switches are Moss# 141-260 or Victoria British # 8-485.|
|lot of power runs through them. easiest way to prevent this and get more power to the head lights is to run power to headlights through relays with only the power needed to switch the power actually running through the switch. Sounds like something is wrong as I haven't heard of it happening that frequently. David Dubois who posts on this site occasionally is pretty knowledgeable in that area. Relay set up example at www.mgb-stuff.org.uk (or uk.org) on Paul Hunts site.|
If you have a problem with a Moss Motors sourced headlight switch, please contact Michael Grant at firstname.lastname@example.org with specifics. If there is a manufacturing problem, we want to address it.
First, make very sure that there is not a short in the wiring causing the switch to melt down. A common problem has been loose side light wiring in the trunk shorting to the body.
|Miswiring the switch will also cook it, at least in my experience. I had the power feed hooked to what should have been the output for the parking lights. It switched the lights properly, but I guess the contacts on that blade aren't up to the task of parking lights + headlights....|
|Failure of a switch due to overheating also damages the connector on the wire(s), by annealing and oxidising it. The connector is then loose and dirty, which causes heating of the connector on the switch, which softens the plastic, allowing the rivet to the internal contact to be loose, which causes more of the same = meltdown. You can help a bit by carefully squeezing the sides of the wire connector, so that it is tight, but it is basically junk once it's been hot. The later connectors with the black hard housing and the stupid latch are worst. They latch on, so you don't realize that there is virtually NO contact. New connectors are called for anytime a connector has been visibly overheated; Relays are the final answer.|
|Thanks for your help. I know how to repair this problem. However, I'm trying to find out if antone else has had a problem with these switches.|
Kelvin, I'll contact Michael today.
|Not surprised, brake light switches from some sources are also rubbish and need relays now.|
Sorry to get on a soap box, but a global statement about parts being rubbish and veiled suggestions to modify original wiring does not help anyone.
John did contact Michael at Moss and there will be follow up. Moss has these switches manufactured, and although the failure rate due to mechanical assembly is higher than we like, it is still lower than average for electrical switchgear. So far there have been no complaints of this type of meltdown, so it is something we are taking very seriously. When Lucas discontinued these switches (141-260 is actually a generic replacement for the 68-72 Federal Spec MGB, not 73-76 as John stated) Moss US stepped in to get them back into production. If there is a manufacturing or quality control issue, we are very concerned and will address it. The intent is not to supply rubbish, but to keep products on the shelf, so the cars will stay on the road. Any reports of failure will be taken seriously and addressed.
Ok, off soap box. It's just that there are really people who care about these problems, even if it doesn't seem like it.
|Kelvin, I think you jumped in too quickly and didn't read what I said in full. I said *some* sources and hence it is not a global comment. The fitting of a relay, whilst highly undesirable to me, may be necessary if one is unable to obtain replacement brake light switches that last more than a few days. The experience with some of these is so bad that the relay also has to have a quenching diode as even the back-emf from the relay will destroy the contacts. This hasn't just come from me.|
|Some difficulty may be from the higher|
current draw of quartz-iodine headlights.
I moved my QI headlights from a 65 midget
(200,000+ miles, original owner), to my
69 MGC. No problem with the original Midget switches, but I cooked a couple of column switches (locally sourced) in the C until
I added relays. It seems the newer switches have a lower current capacity.
I know the relays are not original, but on
a dark rainy night...... I didn't cut the
harnass, but unwound it to add relay leads,
and re-did the cover.
|Alon's been having the same problems wih some of the switches we've ordered from Victoria British. The brake & headlight switches both melted in the back(dash light retrostat went out when the headlight switch burnt out after the third replacement). Heck the headlight switch lasted 1 minute in the on position with me monitoring the electrical supply and a buddy going through the gt's wiring. We still can't fiqure out whats causing it or why. Damned light switch burnt my arm when it melted. We've gone over the harness four times already to fiqure out whats happening to the switches and are still puzzled by it. I've got her running with my spare lucas switches right now with no problems, good thing for her I buy Lucas NOS switches whenever I get the chance. I'll hazard a guess that victoria british got a load of defective switches is all, that or Chris is onto something about the power tolerance differences from the original switches to the replacement switches. Hope not though. At least Alon doesn't have to worry about getting any new switches for a long while since she's got original's now. |
I just wish I hadn't of given her that nos retrostat switch, those buggars are hard to find, so's the oil psi guages annoying rectangular buggars.
Oh well thankfully I've still got one nos headlight switch to use, or more then likely give away to a fellow B owner. *lol*
CJ Dark: Getting ready to head back to the old BL parts storage in _____ for more nos Lucas parts. And No I'm not telling ya'll where its at!! That's my secret!
This thread was discussed between 20/10/2004 and 24/10/2004
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