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MG MGA - light problems, help requested

Hi folks, been a while since I posted last. I have a problem with my MGA 1500 roadster. The headligts work, the front and rear parking lights work. Both front turn signals work,The driver side rear turn signal and brake lights work, but the passenger side brake light and turn signal DO NOT work. I have cleaned all bullet connectors under the rear of the car, and under the hood by the starter switch. Since the rear tail lights work, I know the bulb is properly grounded. Any ideas as to what is probably the culprit? Im guessing the firewall mounted turn signal relay is perhaps to blame. Thanks, Glenn
G Hedrich

RHR bright should be terminal 7 on the eight legged box, so the contact feeding that; but, it is closely related to terminal 5 brake, with two different contacts, so look and see if the contact arm is dead.

First "Since the rear tail lights work, I know the bulb is properly grounded. "
No. You do not. The tail filament will ground through the brake/turn filament, and appear OK. But not usually the other way round, because of the different resistances of the filaments. Check voltage at the wire terminals to see if the 8 legger is sending a signal, then fix the bad ground on that lamp.

FR Millmore

Try swapping the bulbs at the back. You know that the drivers side one works. Does the problem move with the bulb?
Dan Smithers

Switch on parking lights. Switch on key. Step on brake. If the tail light gos out when you step on the brake, it's a bad ground in the lamp.
Barney Gaylord

Hi, everyone.Thanks for your responses! As suggested, I swapped tail lamp bulbs side to side but still no brake light or turn signal. I have ascertained that the defective brake light and turn signal bulb do indeed have a proper ground, so that isnt the problem. When I switch on the turn signal both left and right, I hear the flasher unit cycle on and off. When I activate the turn signals switch both left and right, and watch the contacts in the turn signal relay box, each set of contacts move in relation to the left or right turn signal switch being activated. So Where do I go from here folks? Glenn
G Hedrich

If the flasher cycles, there must be power going somewhere. So, it is either going to earth at an unauthorized short with just enough resistance to not blow the fuse, or it is going through the lamp filaments but not lighting them because there is too much resistance. So you are back to bad grounds or catywhompus wiring.
Get a test light or voltmeter and start checking from flasher onwards, each step in sequence.


FR Millmore

You could have a dirty contact in the relay unit. BTDT and finally replaced it after wasting too much time fiddling trying to fix it.
Barney Gaylord

This thread was discussed between 17/07/2012 and 19/07/2012

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