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MG MGB Technical - Headlights ? & Wipers ?

Well I can tell its Spring, as I'm posting constantly to address the 6 items needing attention last Fall, which grew to 12 items this Spring. On to the questions:

1972 B
Headlights:
All the lights on my car work, although getting the marker and tailights on requires a little rocking of the rocker switch. However, last Fall when switching to High Beams I realized neither light came on. Low beams work and all marker and tail lights come on. When switching to High Beam, the headlights only go out. I have not installed new headlights, as I find it hard to believe both burned out at the same time.

Is there another possible problem?

Wipers:
My wipers used to work, like 2 years ago. Then they decreased in function a year or so ago to the point that if I moved the wiper control arm up and down I could get the wipers to somewhat mimic the movement and they would work. This year, moving the control arm results in no movement of the wipers.

Should I be considering replacing the wiper motor or the wiper control arm assembly? The OD switch in the wiper control arm still functions.

Your thoughts?

P.S. I still don't have the heater box out, can't get the heat vent control knob off to get control out to remove the cable. Box appears still welded in place.

Thanks

BobA
R.W Anderson

Bob,
I'll comment on the headlights. You most likely have a short (or just old age) in the column mounted high beam switch.
I had one once that did the same thing.

As Ronnie Barker used to say on "Open All Hours", try "jj-ii-gggling--g it a bit".
Dave
David Steverson

I see on the "General" board you ask about 2 unattached black wires. Will earthing these restore normal function?
Mike Howlett

Bob, re the wipers. The first thing I would is remove the wiper motor gearbox cover & remove all the soldified grease.Give it a good clean & then see if it works. Barrie E
Barrie Egerton

Soooooo many people say you have a short when you have an electrical problem, and it just isn't the case. If you did you would have smoking wiring and a burned out harness.

If one beam works but the other doesn't, on both light units in each case, then the obvious culprit is the dipswitch or the wiring from it out to the filaments in the headlamps. It could also be the same filament burned out in each light unit of course, or some other *open-circuit* (not short-circuit) in the wiring, which is why you should always diagnose with a test-lamp or voltmeter before splashing out on new bulbs or sealed-beam units. Test at the blue/white (main beam) and blue/red (dipped beam) wires by the dip-switch and the right-hand headlight. Bear in mind you may have more than one fault.

The wiper motor appears to be struggling, but still powered. This problem could be due to (more) bad connections in the 12v and earth supplies to the motor as well as physical binding, which could be in the wiper spindles or rack as well as the motor itself. Wipers like indicators/turn signals are quite difficult to diagnose, physical drag will result in more current which results in more volt-drop in the inevitable resistances between battery and motor. But then resistances themselves will result in more volt-drop and less current through the motor, and both result in slower motor movement.

The heater box itself should still be capable of being moved to some extent even if the cable is still attached to the dash control. If it isn't you have more than one problem. At the end of the day even if you chop through the cable in order to remove the heater unit, you are sioll going to have to remove the control from the dash to reattach a new cable to it. If all else fails then you may have to grind the knob off the spindle, in an attempt to save the control at least
Paul Hunt

Here in the south, "short" means "it ain't working".
David
David Steverson

Yea paul I think you went a tad off the deep end this time. Sounds like your saying your the master of the prince of darkness! If the guy wants he can wire up the motor to a 12v supply and see if the motor starts working. You dont have to get bent because you know more than others on here. Thats why they are here.

James
James

Pot and kettle, James? :o)
Paul Hunt

HA !
James

I hope you two are done :)

Working on the wipers will be less stressful than working on the heater box removal, so I'll try the motor gummed up grease approach or inspection; and move on to checking connections.

Thanks.

BobA
R.W Anderson

James,Paul IS a wealth of knowledge and should be treated as such .
rich osterhout

I am bowing...
James

Has anyone tried the "Power Probe" test units that can be used to apply 12 volts directly to components. I am thinking of buying one. When shown on 2 Guys Garage it seemed like a simple way of knowing if the part worked or if the problem wa in the switch or wiring.
Kelvin Hawkins

Its "Boring" not bowing :)
rich osterhout

'ello,
I have a similar problem with lights. nothing worked at the flip switch (on a '79) but the brights worked on 'flash' from the indicator/horn switch. i bypassed the indicator switch using a new generic toggle from a part store, and both the blue-white and blue-red. now, with the flip switch flipped forward and then the new toggle flipped on, all markers and headlights work. i can even go from low to high beams. of course i don't have the cowl on and alot of wires exsposed - nice fix until i can pull off the steering wheel and get into rebuild the indicator/horn switch.
anyone have advice on that? rather not buy the $80 switch right now. anyway, where's the fun in that?
later,
brady
brady

You might like to have a look at http://www.mgb-stuff.org.uk/wn_electricsframe.htm and click on 'Dip-switch'. That describes one off a 73, it may help with yours. But before fiddling with the switch check you have 12v on the blue coming up from the harness when you have the headlight switch turned fully on. If not, then it ain't the switch.
Paul Hunt

Ha! A case of physician heal thyself! Readying the car for the Yorvik run this weekend, checking the lights, no dipped or mainbeam but the flash works! By the time I'd removed the column cowl they were working again. Wiggled, the switches and multi-plug, steady as a rock. Decided to pull the lighting switch forwards out of the dash so I can test there if it should happen again, and they've stopped working again. But by the time I get my meter out they are working again! So I shall just have to keep going back to it and hope that one time, meter and connections at the ready, it fails again and I work out where the problem is.
Paul Hunt

Gees, I hope you didn't acquire this problem from me through internet information exchange process, electronically! :)

The "physician heal thyself" reference reminds me of a ride with club last year, when my muffler fell off my B on the highway. One of the more comical members berated me for embarrasing the club by having my MG fail in public & provided all sorts of guidance on not having this happen again.

His fell off less than 1 mile later!
R.W Anderson

Rich,

Do you really want to get this NY boy started??? Just kidding... Oh and Paul I love you... Really I do.

-James
James

I'm having the same problem--headlights go out but taillights and side markers still work. Sometimes dash lights and taillights go out and headlights stay on. Sometimes I can wiggle the rocker switch on the dash and everything comes back on. Sometimes wiggling the switch doesn't work. Two weeks ago I drove 60 miles holding the dipswitch on because that was the only way to get headlights on. The taillights worked but no headlights unless I held the dipswitch on. Last year I took the rocker switch out and cleaned it and the problem went away until about a month ago.
Ken
1974 MGB roadster in blaze red
1973 MGB roadster parts car in rust red
Kenneth Thompson

James.....Give it up.....CAUSE i'm a New Yorker ,BORN and Raised!
rich osterhout

Eventually found it was the main lighting switch, and it is only 20 years old! Joking aside I very rarely use the headlights, so it has to be classed as a premature failure. Modern (I almost said 'current') replacement electrical switches are about the most troublesome thing these days, but this is an original Lucas unit (OK OK, cue 'dim, flicker and off' joke). I only replaced it during restoration with all the others because the logos had got a bit scruffy, and as my golden rule is 'if you haven't found a use for something yet you haven't kept it long enough' I still had the old one so fitted that. Given the 20 years it doesn't look that much worse than the 'new' one!
Paul Hunt

This thread was discussed between 30/04/2009 and 20/05/2009

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