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Hazards, Indicators And Internal Light Fault


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#1 Sam Biscuits

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Posted 05 January 2020 - 05:04 PM

Evening everyone. Looking for help tracking down an electrical fault on a Jan 1993 Mini Sprite. The hazards, indicators and interior light have stopped working.

 

Looking at the Haynes Manuel I've struggled to find the right wiring diagram, the 1986-onwards show separate flasher units for the hazards and indicators, but I believe this changed to a single flasher for both from 1993-onwards (under the dash to the right of the steering column), so I'm using the redrawn diagrams from the forum which look a much better fit.

 

Given the hazards, indicators and interior light are at fault I checked the line fuse 1 and found it burnt out. Changed this fuse and have 12v on the fuse input, but doesn't fix the fault. Retested the new fuse and it is ok (image 1).

 

Next tested the 12v input to the flasher unit (pin 49 on the relay installed but pin 85 on the diagram), no 12v found. Also tested the 12v input on the interior light but again found no 12v (image 2). I'm a bit dubious of the quality of the earth doing these checks, using about on the seat clamps for the black probe. 

 

I've also pulled out the hazard switch, taken it apart and cleaned it up.

 

Tried jumpering pins 49 and 49a to bypass the relay, but no change, same with the hazard switch.

 

Has anyone got any ideas on where to go next? Other than replacing the hazard switch and the flasher relay I don't know where to go and given I can't see 12v on the relay input, seems a redundant check.

 

 

Attached Files


Edited by Sam Biscuits, 05 January 2020 - 05:05 PM.


#2 MiddletoM

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Posted 05 January 2020 - 09:02 PM

If you have power at the fuse now you have changed it and dont have power at pin 85 of the relay then that would suggest there is a break in the cable. When testing use a proper ground like the engine ground strap, then you eliminate issues with faults on the loom ground cables.

Do a continuity test between the purple orange cable at the relay and the purple orange cable at the line fuse to make sure there are no breaks in it.

Also check fuse 1 in the in the box just to make sure power is getting to the other relay

 


Edited by MiddletoM, 05 January 2020 - 09:14 PM.


#3 MrE812

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Posted 05 January 2020 - 09:38 PM

There was probably a reason that fuse had blown. Have you checked continuity from the fuse to those points too? assuming you have a multi-meter? it could well be a burnt out / frayed wire.

Given the fuse is now known-good you are right to expect the relay(s) to work. The relay you speak of - sounds like a 3 pin relay? 31 = ground, 49 = +12v, 49a = indicator switch. 

To eliminate the wiring you'd have to inject 12v into the circuits to see if that makes things work.. be careful though, you could be blowing more fuses if you get the wrong pin.

 

Hope this gives you some more ideas for troubleshooting - classic car wiring is a pig.



#4 cal844

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Posted 05 January 2020 - 09:51 PM

The indicator relay Is at the steering column, the hazard relay is one of the 2 relays at the wiper motor. You'll also have an inline fuse behind the carb (purple/orange)
Also check the top fuse in the main fuse box.
The power to the indicators goes through the hazard switch.

Personally I'd check the inline fuse, then change the hazard switch (be careful when changing the switch so you dont earth it and blow fuses).

A power probe is a great tool for diagnosis.

Hope this helps

Cal

Edited by cal844, 05 January 2020 - 09:53 PM.


#5 Sam Biscuits

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Posted 06 January 2020 - 07:52 PM

I found the issue. The 12v input side of the fuse holder had melted a little when the fuse burnt out, so whilst a test prove measured 12v there, when a fuse was inserted it wasn't making contact. Fault sorted thankfully. Thank you for people's advice.






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