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MG MGB Technical - All lights, just no Dipped beam
I am the proud owner of a 1975 MGB GT which is my first car and proving to be much fun. I have a wee problem with the lights. All of the lights work as they should, except the dipped beam headlights. When the rocker switch is turned on once I get sidelights (as it should do) but if I flick it once more onto dipped beam, I continue to get just sidelights. Full beam on the stalk works as it should. Any suggestions?
|It could be a number of things.|
Faulty dip switch.
Corroded bullet connectors behind the grille.
Check the wiring loom behind the grille where the blue/red wire from the main loom goes into a double bullet connector which then feeds both headlamps.
Has the problem just happened, or was it like this when you bought it?
|Dave O'Neill 2|
|It is a problem that has just recently happened. I have had all the lights working and it passed its MoT no problem. I had the grille out and was fiddling about with the wires but nothing seemed to work; I think I will have another go anyway. When you say faulty dip switch, do you mean the rocker on the dash that gives sidelights too?|
|The stalk on the steering column sounds faulty. The stalk has three positions for headlamps. (From memory, the car isn't around at present) The center position is dipped, the position away from you is main, and the momentary position towards you is dipped and main at the same time, used to flash your lights etc. Don't hold this position when it is working as the current is significant.|
If you check what Dave O'Neill suggests, iIf it indeed is the stalk, removing the column cover is straight forward, if fussy. Then you can remove the screws holding the stalk. Drill out the rivets holding the spring leaves, and bend them into position, and then use a small screw and nut (with a lock washer) to reassemble. Test with a ohm meter to verify function.
|Thanks for that, Dave and Dave. The dipped headlights are not stalk operated. There is a rocker switch mounted on the dash near the choke which at 1st position is off, 2nd gives side lights and 3rd gives dipped headlights.|
The stalk then gives full beam if pushed away, flash if pulled toward driver and direction indicators if moved up or down. All of these functions work so I dont think it is the stalk.
Will recheck the wiring and report back!
When the stalk is pushed away, it switches off the dip and switches on the main beam.
|Dave O'Neill 2|
|Just had the same problem last week and it was a corroded bullet connector, left side behind the grill (looking from the front). Nice cheap fix!|
|James. As Dave O. suggests, the rocker switch provides power to the side lights, parking lights and rear lights in the first position. In the second position it provides power to the headlights through the stalk on the left hand side of the steering column. When the stalk is in the central position, power flows to the low beams (dipped beams) and, when pushed forwards to the high beams (main beams). |
Get a copy of the wiring diagram and a test light. Turn on the lights and check for power going to the headlights when the stalk is centralized. If you have power through the switch, the problem is further forwards. If you do not have power through the switch, the switch is bad.
If the switch is bad, jumper the wires and see if the low beams come on. If so, your wiring is good forwards of the switch.
If you have power thought the switch, or have jumpered the wires with no low beams, continue checking for power towards the headlights to see where the problem is. When you find power on one wire, but not through the connector to the next wire, clean the connector and continue working to the lamps until you have power. Do not forget that headlights do burn out. But, this normally happens to only one of them at a time.
|What the Dave and I are saying is just about the only reason we've ever taken apart a stalk switch is to repair it for either dipped or main beam operation. The little leaves can fail, leaving one or the other inoperative. The dipped headlights are stalk opperated.|
The power goes like this:
A purple (fused, always hot) wire to the stalk switch to provide power all the time for the flash to pass momentary portion of the switch only.
A brown (unfused, always hot) wire to the panel light switch, with red with green leaving for the parking lights and panel lights (first position) and also a second blue wire going to the stalk (second postion).
The stalk then has a power source (the blue wire) to use to select the blue with red wire for dipped (normal position, but it is still a position) or the blue with white wire for main (pushed away position). You have main beam so the dash switch is functioning. You don't have dipped beams so the stalk or the wiring after the stalk is not functioning. The head lamps have a common ground. Since the main beams are working, you have a ground.
So you see, the fact that you have main beam and not dipped beam could be in the wiring between the stalk switch and the head lamps (the blue red wires) or in the stalk switch itself. The flash to pass momentary position (pulled towards you) gets its power from another source, so you don't have to have the lights on to select the flash. It is also a functions on a separate set of contacts from the main or dipped selections, so it can work regardless of the function of either the headlamp switch or the other stalk functions.
I hope this clarifies your possible reasons to examine the stalk switch if your wiring after the stalk switch checks out.
|oops, simultaneously posted with Les!|
In the UK, the stalk is on the right side of the column.
|Dave O'Neill 2|
|Dave B. Never hurts to provide similar information in slightly different ways. Who knows which one will work best for any individual? I find that tracing power forwards works best for me. Others find that tracing power backwards works best for them. In the end, either method works.|
Dave O. Does the switch on the right also contain the turn signals? Here in the US, it is turn signals on the left, along with the dip switch, while the windscreen wipers are on the right. But, when I lived in Germany, my BMW sedan had left hand drive with the turn signal switch on the right side of the column. I had always assumed that the UK cars had the same set up as the North American cars, except the steering columns were on opposite sides. This seems not to be the case.
I would be interested in learning what the turn signal/wiper controls were on both the Home Market cars and the Export/non-NA cars if anyone has the time to post such information.
Yes, turn signals and headlamp dip/main were always on the right for the UK market - except when dip was on the floor.
Wiper switch was on the dash until rubber-bumper models, when it migrated to the left side of the column, along with the overdrive switch, where fitted.
|Dave O'Neill 2|
This thread was discussed between 11/07/2007 and 12/07/2007
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