• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

MGB MGB - Left turn signal wont flash, brake light dim

Share this page

Scott_Hower

Scott_Hower

Luke Skywalker
Offline
Looking for some advice... car is a 73 MGB.

The left side rear turn signal refuses to flash and the brake and parking lights are VERY dim. All bulbs (all around) are fine. I thought I had bad grounds, so I ran a seperate ground to both L side bulb sockets. Still cannot get the L rear to flash. The right rear brake/flasher works fine.

The hazard flasher also works fine, front and back on both sides flash, although L side is dim.

Anyone have any ideas?
 
My first thought is that your power is grounding out somewhere along that rear harness. Easy way to test it to connect the left hand light to the right hand connectors. If the light works there then work back along the harness. If not then you can narrow the problem down to the socket.
 
Ok, thanks. I have some jumpers with bullet ends, I'll wire the left side lights to the right side connectors to isolate the problem and see what happens.

I'm guessing they will work fine, which suggests something in the loom between the left and the right (the right side powers the left via double connectors).

I keep forgetting that resistance changes can screw up the flasher circuit. Maybe the connectors are just toast.
 
Re: MGB - Left turn signal wont flash, brake light

is the battery fully charged? as simple as it sounds, that could be a reason for the dim lights/flashers.

also, when the hazards flash, do they all flash at the same time, or do they alternate? (which would indicate your wires connecting to the e-flasher unit are switched)

also, what condition is the fusebox in? a little bit of corrosion can really add to your headache.

just a thought.
 
Re: MGB - Left turn signal wont flash, brake light

[ QUOTE ]
is the battery fully charged? as simple as it sounds, that could be a reason for the dim lights/flashers.

also, when the hazards flash, do they all flash at the same time, or do they alternate? (which would indicate your wires connecting to the e-flasher unit are switched)

also, what condition is the fusebox in? a little bit of corrosion can really add to your headache.

just a thought.

[/ QUOTE ]

1. Battery is newish and fully charged.
2. Lights all flash in unison, including the directional and console indicators.
3. Fuse box is original; looks like a new one is about to be added to the list.

Dont know if this matters, but I bled the brakes and this problem happened (or at least I noticed it) when I was finished. I could swear that I read somewhere that if the PWDA shuttle gets offset to one side (brake failure switch) weird stuff like this is a result. I don't really see how if could after tracing the circuit in the Bentley book. It just grounds the bulb in the failure switch on the on the dash causing it to light. /ubbthreads/images/graemlins/confused.gif
 
Re: MGB - Left turn signal wont flash, brake light

couldn't tell you about the PWDA, haven't had an issue with that yet.


as far as the fuse box, clean it instead of replacing it, just make sure you know where your wires all go.

What I did is I took it off the inner wall, removed the fuses, and sprayed some battery corrosion eater (stuff in a can for about $5) all over it and let it sit for about a half hour. Rinse well with water and squirt it again. any corrosion that is there will show up as a pink color. (the spray comes out foaming yellow). do this a couple of times until it is clean. rinse well, dry it off (or let air dry for a while) then put it back on the car. I did this because one of the hot leads going back to the tail-lights was only sometimes working. it wasn't making a good connection at the fuse box at the time. Now, it is a strong contact point.

I'm sure someone will come along that can get you an answer on the other part of your electrical issues.
 
Re: MGB - Left turn signal wont flash, brake light

Just my 2¢, but did you check the brake light switch? Mine did some pretty funky things a while back (until I got some advice on adjusting it).
 
Re: MGB - Left turn signal wont flash, brake light

Thanks; switch is newish (~ 2 years old). I'll check the pedal freeplay and add jumpers to take it out of the loop when testing.
 
Re: MGB - Left turn signal wont flash, brake light

Scott,

First, welcome to the Forum from another PAer /ubbthreads/images/graemlins/savewave.gif

It sounds like you are getting there...just one more thought based on my experience...a long shot...Pull the connections on the second harness split in the trunk for all the lights and clean them. This spot in suceptable to loose item is the trunk mashing the exposed wires there...the top wire get the most abuse. Make sure the old brittle wires are not cracked to badly or broken and reconnect. If you have an ohm meter, check this stretch of wire, moving it around to find any weak spots as you check the meter. Yes,that how I fixed the exact same problem that was covered in paint...peel it back and rejoin, solder and tape...good as new /ubbthreads/images/graemlins/grin.gif

Good Luck!

Bruce /ubbthreads/images/graemlins/cheers.gif
 
Re: MGB - Left turn signal wont flash, brake light

Thanks, I'll give it a try.

/ubbthreads/images/graemlins/savewave.gif I'm located near Allentown. You going to the Carlisle Import show in May?

Here's a couple of photos of the culprit:

mgfront.jpg

enginebay2.jpg

boot.jpg
 
Re: MGB - Left turn signal wont flash, brake light

Holy #$%%, wow Scott that's one AWESOME looking B. Its breathtaking. You sir, must be one proud papa. /ubbthreads/images/graemlins/cheers.gif
 
Re: MGB - Left turn signal wont flash, brake light

Check the ground wire on the light itself. Use a secondary wire with clips and ground the light base to a known ground like a bumper bolt or fuel tank retaining bolt. It this correct the problen then make sure that the actual terminal is clean and the stud it attaches to. Also check the other end of that ground wire where it attaches in the centre of the trunk unter the latch hook. If no ground then the double fillament bulb uses the other side of the circuit for grounding ie. the clearance light grounds through the brake light to the other side brake light then to ground there - added resistance results in slow blinker and dull clearance.

Look for you at Carlisle. We're going Thurs and camping on site. Regards, Bob
 
Re: MGB - Left turn signal wont flash, brake light

[ QUOTE ]
Check the ground wire on the light itself. Use a secondary wire with clips and ground the light base to a known ground like a bumper bolt or fuel tank retaining bolt.

[/ QUOTE ]

Thanks, Bob. The light in question is grounded via the mounting studs, it doesn't have a seperate ground. I did use a jumper from the housing to a good ground in the boot. The light got slightly brighter (suggesting I should add a seperate ground), but still wouldnt flash. I'll have some more time tonight to noodle with it.

I'm arriving Carlisle Friday AM. Probably in the BMW section on the "fun field". Will drop you a PM as date approaches.
 
Re: MGB - Left turn signal wont flash, brake light

[ QUOTE ]
Check your hazard light switch.

[/ QUOTE ]

Thanks; thats the first thing I suspected as the signals are wired through it. Works fine and lights flash (albiet dim on the left).
 
Re: MGB - Left turn signal wont flash, brake light

It being dim on the left is suspicious. You might pull the switch out and clean the connections and see if it helps. I had a similar problem in my '73 and actually replaced the switch. No problems after that.
 
Re: MGB - Left turn signal wont flash, brake light

Had some time yesterday to diagnose some more. I removed both taillights. The right side had a loose bullet, so I soldered a new one on; I cleaned the others with emory cloth. I replaced all of the rubber bullet connectors. I also added seperate pigtail grounds for each tailight. The taillights are now bright on both sides. The left front sidelight is now very dim. The connections looked good; I removed the bulb and the housing/contacts are pretty corroded. I ran out of time, but I suspect the problem is high resistance here.

All of my switch gear is relatively new.
 
Back
Top