electric fault

[mrb]

Hi
Anybody out there with good electrical knowledge ? who may be able to assist me ?

1968 1000 - oil light was not lighting up - so l took the wire off the switch - put it to earth on the body - the light still did nt work !
so l removed the speed head - replaced the bulb - which did appear to have blown - checked all others too ! refitted the head - but now l seem to have re-created blackpool illuminations

when l switch on still no oil warning light - checked by earthing the switch wire again - still no light !
But when l switch side lights on "main beam glimmers" when l switch on headlights - well now oil light warning light illuminates

Does anyone know what silly me may have done ?


Thanks DAVE

[aupickup]

you have the 2 wires mixed up on the speedo change them round that might do it

[mrb]

Thanks

But tried that one ! only had the main beam and oil light out to change bulbs - felt sure l put them back correctly

Checked wiring but seem s to have changed colour or it s wrong in Haynes Manual looked to see if l had perhaps

disturbed a earth ?

[philthehill]

The correct colours as stated in the BMC Service Manual is:-

Oil pressure switch to oil pressure warning light - GREEN with YELLOW stripe.
Oil pressure warning light to snap connector - GREEN.

Head light main beam warning light to snap connector - BLUE with WHITE stripe.
Snap connector to dip switch - BLUE with WHITE strip.

Did you put the right wire in the right snap connector?

[picky]

So your oil pressure warning light is now behaving exactly the same as the full beam light? are they both on or off at the same time?

[bigjim]

would hazard a guess at a bad earth so main beam is earthing through oil light and vice versa

[simmitc]

Are the bulbs with the red wires in the holes to illuminate the speedo? If you turn the instrument lights off (slide switch under dash) do any of your now bright warning lights go out? Are all bulb holders firmly in the sockets, and is the speedo securely fixed to the dash - that's how the earth return is made.

[mrb]

Thanks to philthehill for colour check - will re-check in day light - do feel sure l replaced correctly but who knows at my age anything can go wrong "thanks"

Thanks picky - just ign light on when ignition switched on - then put h/lt flick switch into position one "side lt" main beam "blue light glimmers" then flick switch onto position two and oil warning light comes on too ! - am going to attempt checking wiring colours tomorrow but "tHANKS"

Thanks big jim - cant find a earth behind speedo head - but got some checking to do as above Thanks

Thanks simmitc another line to check thanks pleased earth comes via speedo and dash am actually working with the head
dangling freely Thanks
Dave

[simmitc]

Just another thought - the oil pressure warning has a feed from the switched ignition, and makes its earth return via the switch, but I think you knew that anyway. The reason for my asking about the bulbs with the red wires is that they come on with the side lights, and so you could have one of those in a warning light hole to give some of your symptoms. You can get an earth for testing by just holding the speedo to the dash. A better way would be a short wire with a couple of small crocodile clips. Final complication - there might be a redundant oil filter warning light there too, and over the year, a previous owner might have moved the wires and the bulbs around Good luck.

[philthehill]

I tried posting the wiring diagrams from the BMC Minor Manual on here but could not get them clear enough to read so it would not be of much benefit.
Having looked at the BMC wiring diagrams I am pretty sure that you have got your wires mixed up. Check the wire colours in the daylight against the wire colours details given above.
If you have the later type trafficator control or flashing indicators the wire from the snap connector to the oil pressure warning light is GREEN and the wire from the oil pressure warning light to the oil pressure warning light switch is GREEN with YELLOW stripe.

[bmcecosse]

As above - it's mixed up bulb holders in the wrong holes in the speedo.... nothing to do with earth since oil light and Ign light don't rely on earth through the speedo. Pretty sure the speedo has a direct earth cable connection anyway - it's been a while since I had one out!

[beero]

Earthing could be a problem, I took my speedo out and when I put it back in the fuel gauge didn't work. I had to run an earth wire to one of the side fixing screws for the speedo before the gauge worked.
You may also have got the lamps mixed up but lack of earth won't help.

[mrb]

UPDATE --

Thanks to all who assisted my request - Today l seem to have made a little progress !

First "yes" seemed to have wrong positions in speedo head - following helpful wiring instructions - rectified this problem

But still have the main beam light on when head lights on - although it does get brighter when dip switch operated !

and yes oil light switch still not working took wire off the switch and put to earth ! changed bulb for a new one still not working

So l think it may require a trip to a auto electrician


But thanks to you again Dave

[aupickup]

can you try another head where the oil switch is

[chickenjohn]

The best place to start for electrical problems is a wiring diagram.

At the back of the manual you will find wiring diagrams, check the wire colours correspond to what they are supposed to connect to.

Then check all connections for corrosion. Most electrical problems on classics are down to corrosion in contacts and wires being put back wrong.

[mrb]

Have not got a spare head to check oil light !

Think wiring all in correct places now - have checked earths " well the one s l've found "

Am having a auto electrician to have a look on Friday


Thanks For help

Dave

[simmitc]

Do you have a multimeter? You need to check whether there is power getting to the bulb holder for the oil pressure warning lamp. Also check that when the wire is earthed at the switch, the other wire on the bulb holder has a good connection to earth - and that there is no connection when the wire is removed from earth. This fault could be a lack of power, or a broken wire to the switch - or even the wrong wire.

For the high beam warning light, you should have a thin blue/white wire that goes to a 4-way bullet connector with two thick blue/white wires and one spare hole. I suspect that you will find it connected to an all blue wire which is the feed from the on/off switch to the dip switch. Dip beam is a lower power than the main beam, so there will be more power left to make the warning lamp glow brighter.

[Roni]

For the main beam warning light, check if there is a small rubber boot between the place where the bulb clips in and the warning light outlet on the face of the speedo. If it is not there, or displaced, there may be some stray light from the speedo illumination lamps leaking through thus showing the light always slightly on when the lights are on. Check it the easy way by using the face illumination switch under the dashboard, lights on, speedo illumination lights off.

[bmcecosse]

" Dip beam is a lower power than the main beam, so there will be more power left to make the warning lamp glow brighter. " Ehhh???

[simmitc]

It's simple: dip beam lights draw less power than main beam (lower wattage), so any other light that is on at the same time will dim slightly when main is selected - try it by looking at the courtesy light and operating the headlights. The extent of the effect will vary with the wattage involved, but if the warning light is on the same feed as the headlamps, it will be seen. The battery is not an infinite source of power. This effect can also be measured with a voltmeter.