MGB 77 MGB Turn light dashboard indicator

[Petizo]

On my 77MGB all the turning signals were working ok including the indicator on dashboard, all of the sudden the left signal indicator on the dashboard does not flicker any more. I removed the light bulb and tested it and it worked ok, if I turn on the hazard light, both indicator on the dashboard light up. Does anyone knows what can cause this? maybe the turn light switch??

Thanks,

 

[90 XJ-S]

Do the lights on the left hand corners of the car light?

Mike

 

[Petizo]

Hi Mike,
I have checked all the lights and they are all in good working order, if I set the turn signal to the left the lights flash as they are supposed to, the indicator in the dashboard does not.
I am thinking is the actual switch.

Jorge

 

[Bret]

Hmmm? My money is on your Hazard Switch.

This was a long time ago but I seem to remember a similar problem with my 78B when I first brought her home. Same basic description of the problem hazard flashers worked but the turn signals wouldn’t.

I think my problem turned out to be the hazard switch itself. Try removing it and use some contact cleaner (Radio Shack or some electronics store) to clean the contacts. If you have a Bentley or a Haynes Service Manual you’ll find that a substantial amount of the car’s circuitry comes & goes through that little switch.

Now I had other electrical issues with my car but I ended up replacing the hazard switch.

Good Luck!
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[90 XJ-S]

[ QUOTE ]
...Same basic description of the problem hazard flashers worked but the turn signals wouldn’t.

....I think my problem turned out to be the hazard switch itself....

[/ QUOTE ]

I agree with Bret! Same thing happened to me.

Almost guaranteed to be one or the other of those two switches. And it's a whole lot easier to do the hazard switch (and I think more likely)
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Mike

Interestingly, I have the exact same problem in my Jag.
Lord Lucas... Our friend!

 

[fadler1]

If that does not do it and Brett knows his stuff.........then it is the same as my 1977 perhaps. It turned out to be that fuse #3 was arching at the fuse box. I replaced the fuse box and made sure that the insulation behind it was good and voila............worked fine again. That was a heck of journey to get to that point including changing our many of the wire joints, turn signal switch, etc. A new fuse box WITH COVER is about 25 bucks from Bee Hive. Don't buy an old one. Chances are that the same old bakelite it cracked...........

 

[Bret]

[ QUOTE ]
If that does not do it and Brett knows his stuff.........then it is the same as my 1977 perhaps. It turned out to be that fuse #3 was arching at the fuse box. I replaced the fuse box and made sure that the insulation behind it was good and voila............worked fine again. That was a heck of journey to get to that point including changing our many of the wire joints, turn signal switch, etc. A new fuse box WITH COVER is about 25 bucks from Bee Hive. Don't buy an old one. Chances are that the same old bakelite it cracked...........

[/ QUOTE ]

Ah quit it, you’re making me all misty. /ubbthreads/images/graemlins/blush.gif

Anyway this brings up a good point. A lot of folks only address electrical issues as they arise. Nothing wrong with that, but given the history of Lucas electronics and what I’ve found while working on my car. I would say that the suggestion of replacing or at least cleaning the fuse box like I suggested with the hazard switch is a great idea. Even if everything seems to be working fine. IOW think of it like "Preventative maintenance", just like changing the oil.

One of the biggest issues in dealing with older car’s electronics (not just Lucas BTW) is that corrosion, grease, grim & carbon can build-up on connections and increase power consumption. Or worst yet complete loss of circuit continuity (ground being very common). Sure components can get tired and need replacement, but in the world of electronics it is quite often the simple or cheapest item that has gone south first. Then damages the higher dollar items. So to simply replace the malfunctioning component might be correct – further thought should be given to why that failure occurred in the first place. Another aspect to this is that too often folks try to crank up the power, only to damage new components and other wiring.

Believe it or not the simple act of measuring the resistance of a wire from point A to point B can tell you volumes.

I know this is a bit boring to those of you that know me, but I am probably the biggest advocate of having a multi-meter in every tool box. You don’t have to be an Electrician or an Electrical Engineer, but if you arm yourself with a multi function meter (ohms, volts, & current) & a schematic you should be able to diagnose down to the basic component level.

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[CDNMGBguy]

P. check to see if it makes a difference what position your hazard light switch is in - yes really!! If your signals function with the hazard switch in one position, but not the other, or some variant, then it is time to replace the hazard switch. It is easy to do and fixes the ills. Generally if this is the case the switch is coroded time to replace. This happened with my 80 B.
Also I do agree clean the fuse block, it helps. Use the switch cleaner from radio shack. Good luck.

 

[Petizo]

Well,

Sorry about the delay, I have been kind of busy and did not have the time to check things out until today. I went and just pulled the hazard switch and wiggle all the wires behind it and voila, The light started working again. That was the last place I would have tought, I thought for sure it was the signal switch.

I went today to the automotive section of wallmart but they did not have the contact cleaner, I guess I will have to go to Radio Shack. Also I will follow the advice of replacing the fuse box. About 2 weeks ago I took the car out at night and I noticed that some of the lights were off. Sure thing I started taking bulbs out and testing them but they were all ok. The funny thing is that the lighs were off across ie, front driver side, back passenger side. I went an play around with the wires on the fuse box and all the lights went on then. I has been working ever since but I know it has to go. I am getting ready to store it for the winter, once is done I will have some time for it.
I will like to thank everyone for the invaluable advice. Hey Bret my B looks like a beat up version of yours ;-)

 

[Bret]

Glade you got the turn signal issue figured out. As for the other lights – it sounds like a blown fuse or some of the contacts on the fuse block need cleaning. If you’ve addressed that already and still have the problem, then you have a couple of other issues with your wiring or you might have simply lost or have weak ground for that particular circuit.

A quick test – would be to use a multi-meter and measure the voltage going to the light itself. It should be ~ 12volts (duh?) +/- a volt or two, if much less that that then you probably have a high resistance line. Common problem with older wiring harnesses. If NO voltage is found in the socket - find a good ground point and re-take the measurement again. If you get a voltage reading then it means you lost your ground if still no voltage – you’ll need to follow the wire back to its origin to see where you lost voltage.

For a low voltage reading:
Follow the wires (using a schematic) back to a common point like say a connector or the fuse block. Taking the time to measure the wire resistance from the common point back to the socket or starting point. Typical resistance reading should be less than an ~ ohm any thing higher than that and you will need to either clean the contacts or re-terminate them – worse case replace the wire but only as a last resort. Caution: when measuring resistance car’s ignition should be off - better yet be really safe & disconnect the battery altogether.

Another way to check for a high resistance wire would be to measure the voltage drop across the wire (ignition on). This is done by first turning on the circuit in being diagnosed (in this case the light switch) and measuring the voltage between the socket & the common point as mentioned above. If more than a few milivolts (ie. 0.5 vdc), you’ll need to either clean the contacts or re-terminate the wire connections.

PS be sure to post some photos of your B when you get the chance?
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