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Interesting turn signal problem & Where is flasher unit?

Posted by JohnfromSeattle 
John Mandella
Snohomish, USA   usa

HI, just bought a 1975 MGB. Last night he turn signals stopped working.

>> I checked the fuses...everyting is OK, no blown fuses
>> Hazard lights work fine. They blink on the dash and around the outside
>> Wipers, headlights, high-beams all work fine

I'm thinking the flasher unit needs to replaced. ANy thoughts?

I looked for the flasher under the hood (per my motor manual) but can't find the darn thing. Does anyone know where the turn signal indicator is located?

thanks

PaulP Avatar
Paul Peterson
Seattle, WA, USA   usa
1973 MG MGB GT
1974 MG MGB

If it's like my '74 it's a 2 wire retangular unit just above the passenger's feet.

Welcome!! Good to see more WA folks on the board. Seems like the southeastern US has us outnumbered.

Are you going to the ABFM in Portland this weekend?

Paul

Kimberly Avatar
Kimberly ?
Pinole, CA, USA   usa

You need to check to see if you have power going in and coming out of the hazard switch (two green wires connected to the hazard switch). Hazard lights have a different power source.

Wiring diagram is available for your car at http://www.advanceautowire.com click on stock schematics.

Usually the contacts in the hazard switch become corroded. Try turning on and off the hazard lights a few times and see if the turn signals work.

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John Mandella
Snohomish, USA   usa

Paul,

Thank your for your insight. I'm a bit new to working on MGs. Was the flasher unit hard to find. Did you have to remove the glove box?

Last question...given that nothing else went wrong (hazard, hi-beams, headlights, gauges all OK) do you think the falsher unit is the culprit?

I lie north of seattle, how about you

JOhn M.


John Mandella
Snohomish, USA   usa

I Kimberly,

Thank you for your advice.

PaulP Avatar
Paul Peterson
Seattle, WA, USA   usa
1973 MG MGB GT
1974 MG MGB

John - I'm thinking Kimberly is giving you the better answer.

My flashers worked very slowly when I first got my Bs. Replacing the flasher got them back to working at normal speed again. Does the green dash indicator come on at all and just not flash?

You may want to take some crocus cloth to the ends of the fuses and connectors in the fuse block too.

On the '74, the flasher unit is in plain sight just inboard of the w/wiper motor.

We're in the S end.

Paul



Edited 2 time(s). Last edit at 2006-09-01 01:46 PM by PaulP.

John Mandella
Snohomish, USA   usa

Hi Pual,

The flasher bulbs in the dash don't come on at all when using he turn singals. They blink perfectly (along with all the exterior lights) when using the hazards.

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PaulP Avatar
Paul Peterson
Seattle, WA, USA   usa
1973 MG MGB GT
1974 MG MGB

From the wiring diagram Kimberly provided, it appears the quick check would be to just take a short piece of wire and jumper the terminals of the flasher unit with the turn signal switch in either the L or R position. If the L or R signals come on steady, you know the problem is in the flasher.

Since the T signals and hazzards are powered via the same fuse, you know it's not anything upstream of the hazard switch. As Kimberly suggestion, give the hazard some on/off cycles.

If you have a test light or volt meter, see what you get between the green wire at the flasher and ground. If the light lights or you get 12+ volts, you know you have power at the flasher and the hazard switch is OK.

Check those two things and report back.


Paul

Nathan Lawless
Monroe, WA, USA   usa

Hi John
I experienced the same phenom in my 80 B. Replaced the flasher unit and all is well. I happen to have a 2nd unit that you can have; I'm in the Monroe area, work in Everett.

DrewFletcher Avatar
Drew Fletcher
Kansas City, MO, USA   usa
1976 MG MGB

John-
I had the same problem with mine a couple of weeks ago. By far the easiest electrical fix ever. Seems my daughter kicked the relay with her feet so the wire looked like it was still on the relay but it was just the plastic cover holding it on.

John Mandella
Snohomish, USA   usa

Hi Nathan,

I live in the Monroe area as well. I have not yet tried to locate te flasher unit (yard work ---argg). If it is the problem, I'd like to buy your spare.

How can we talk? My home email is jkmandella at hughes.net

Many thanks

JackMG Avatar
Jack Lindler
Greenville,SC, USA   usa

Do your headlights work? I think if the haz switch is causing the turn sigs to not work, the headlights won't work either. If the headlights and turn signals are out, try rocking the haz sw back an forth. If it's just the turn signals, look elsewhere.

Had my old 76 go completely dark on I-85 in the middle of Nowhere, NC, when my wife planted her purse on top of the console going 60-70mph. Rocked the haz sw slightly, not enough to bring the hazs on, but enought to switch everything else off.

Sinewave Avatar
T. Keith Vezina
Kenner, LA, USA   usa

I've had better results with a cheap, universal flasher than the $15 Lucas unit. It seems that the Lucas ones are much less tolerant of low voltage; the more stuff on, the slower they would flash.

Keep in mind that the lead to the flasher must pass through a set of contacts in the emergency flasher switch. Removing the plug from the back of the switch and spraying a little CRC Electronics Cleaner on the connector and inside the switch has fixed the very problem you are describing.



T. Keith Vezina
British Motoring Club New Orleans
1976 MGB, 1976 MGB Trailer & 1967 MGB MK. I

Kimberly Avatar
Kimberly ?
Pinole, CA, USA   usa

PaulP Wrote:
Quote: From the wiring diagram Kimberly provided, it appears the quick check would be to just take a short piece of wire and jumper the terminals of the flasher unit with the turn signal switch in either the L or R position. If the L or R signals come on steady, you know the problem is in the flasher.
Since the T signals and hazzards are powered via the same fuse, you know it's not anything upstream of the hazard switch. As Kimberly suggestion, give the hazard some on/off cycles.
If you have a test light or volt meter, see what you get between the green wire at the flasher and ground. If the light lights or you get 12+ volts, you know you have power at the flasher and the hazard switch is OK.
Check those two things and report back.
Paul

PaulP-

The hazards get fused power ( there is an inline fuse holder for the hazard lights ) from the brown circuit. The turn signals get fused power from the green circuit ( third fuse down in the fuse box ). That's why the hazards will work and the turn signals will not work when the car is off. The hazard switch is an A - B ( or on-on ) switch. It has no true on/off function. When the hazard lights are off, the switch closes the connection for the turn signals and when the hazards are on, the switch opens the connection to the turn signals. The switch can fail, become corroded, and allow the hazards to work and not the turn signals.


John Mandella-

To test the flasher, you should have a steady 12 volts on one of the connectors ( input ) going to the turn signal flasher and a blinking 12 volts on the other connector ( output ), when the hazards are off. The hazard lights use a different flasher. You can also bypass the flasher by connecting the two wires together and with the turn signal switch in the left or right position one side of the car should light up and not blink. If the flasher is bad, it can be replaced with a generic two conductor flasher available at any auto parts store.








Edited 3 time(s). Last edit at 2006-09-02 06:04 AM by Kimberly.

tdelony Avatar
Tim Delony
CA, USA   usa

I will second what Sinewave said about the Lucas flashers, I bought a replacement one and it had the same problem as my existing one; I went to Autozone and got a $3.99 generic flasher and it works perfectly.



Edited 1 time(s). Last edit at 2006-09-02 09:32 AM by tdelony.

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