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MG Midget and Sprite Technical - Head Lights and relay switch

I have a question about how testing relay switches. I put in halogen headlights plus a heavy duty electrical harness for them. I have had problems with the headlights working. Sometimes yes, sometimes no and I am beginning to suspect the relay switch.

So how would one test a relay switch?
Thor Patterson-Ritz

Trek to radioshack and get yourself a 12v buzzer, Hook the red wire to the relay coil feed (from the original switch) and the black wire to the relay output to the lamps.

If the relay ever gets a signal to turn on, but fails to turn on then the buzzer will sound. You can test this by removing the earth from the other relay coil terminal.
Will Munns

the relay should be wired thus:

85 -> original switch
86 -> ground
87 -> Lamps
30 -> Fuse

85 and 86 may be swapped.

87 and 30 may be swapped.

Will Munns

As an aside, I am about to stick relays on my headlights and from untangling the wiring diagram it looks like the line to the headlights is unfused (seems to come from terminal 7 on the fusebox, which is the unswitched circuit pre fuse). I take it putiing one in line would be a reasonable idea?
Steve

I always thought that the idea of NOT using a fused supply to the headlights was to avoid putting something else in the circuit that could fail, plunging you into darkness just as you approach that 90 right in front of the barn wall at 65 on wet cow-sh*t splattered tarmac. Worse than that, something actually designed to fail!
Not sure that it is sound logic though!
I do know that we fitted relayed lights and spots with separate fused supplies to each on our rally mini 35 years ago. That was after the above mentioned incident which I still remember clear as daylight - only it wasn't! I was navigating that night!
Guy Weller

Guy. Not MG related but you reminded me of a COW-PIE incident of mine.
I was stationed in France with the RCAF and lived in a small town in Belgium. En route was a little village that all the residents seemd to have cows that they brought home at night and returned to the field at approx 0700. We all tried to miss the fresh plops but also drove through with our windows closed. One early morning I was going to work and met another RCAF car coming the other way. He had his window open and I hit a pie just as we met. You know the results. It was the subject of much ridicule in the base canteen.
Sandy Sanders
conrad sanders

If you're a brave man you can change the wiring so it pulls to ground (just remember to fix the flash circuit as well as the normal lights or smoke will be forthcomming) that way you can use relays and fuse the lamps in the engine bay. If chaffing occurs behind the dash (most lightly place) the lamps will lock on rather than lock off, with no smoke forthcomming.
Will Munns

Interesting,...I didn't type that * in place of an i! The BBS morphed my anglo-saxon word!

Just down the road from me here, if you drive at the wrong time of the day you are likely to be confronted by 180 cows slowly plodding and plopping their way back for afternoon milking. In the narrow lane they push and barge their way past the car. It hasn't happened yet but I can tell you that when sat in my Sprite I do feel exceedingly vulnerable to the direct effects of a full day's diet of fresh green grass!

Wots this got to do with light fuses?
Guy Weller

Following the bovine thread of this forum,I once went for a walk on the Solway marshes, leaving the midget by the side of the road (open as I didnt have a hood fitted at that time). When I returned it was surrounded by about 30 cows, after shooing them away ( thats alot of beef) found they had licked the whole car, every inch, inside and out. The exterior I could live with but the drive home wasnt nice. Then I bought a hood!
mike

Mike

Did it have leather seats? They may have recognised a relative!
Dave O'Neill 2

This thread was discussed between 28/07/2008 and 30/07/2008

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.