A few weeks ago I was on the forum with a problem with the control box on our'68 minor 1000. It turned out that the probable cause was a faulty lighting switch and or corrosion on the back of the control box.
I replaced the switch with another I had and rewired the brown blue cable from switch to control box as this showed signs of heat.
As I have been considering an alternator for some time I thought that it was no use buying a new control box so I bought a new alternator kit from a Minor specialist.
They suggested the following connections
leave dynamo connections as were but put them on outer large and small connectors on alternator. Take new cable from middle connection on alternator to solenoid earth side.
Join all thick cables ex control box together, join thin cables together and take the two earth cables to a new earth on bodywork. The particular kit uses a standard fuse box to make these connections.
As I had had problems with the lighting circuit I asked if I could put the blue brown lighting wire onto the other side of the "new fuse" box to give a bit of security. They advised this was ok and we put in a 35 amp fuse.
All is fine when I start the engine and leave on tick over with all lights, indicators on but when I go out for a drive the 35 amp fuse blows.
So the question is, does the alternator put through more than the fuse amperage or do we have a short somewhere that is being shaken when we drive?
Dave
Lighting circuit current?
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Alec
- Minor Legend
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Hello Dave,
"So the question is, does the alternator put through more than the fuse amperage"
In a word, no. That is not how it works, it is the load that draws the current not the source. Assuming standard lamps you have about 6x6 watt side\tail\ number plate lamps, 2x60 watt head light on mains beam plus instrument lights, say about 160 watts, which equals a bit less than 14 amps, so there is possibly a short. Howver, I do seem to remember that Lucas fuse ratings are not continuous i.e. a 35A fuse won't carry 35 A all the time. I really don't know it's continuous rating but I certainly would never fuse all the light circuits through one fuse, as a failure leaves you totally in the dark.
Alec
"So the question is, does the alternator put through more than the fuse amperage"
In a word, no. That is not how it works, it is the load that draws the current not the source. Assuming standard lamps you have about 6x6 watt side\tail\ number plate lamps, 2x60 watt head light on mains beam plus instrument lights, say about 160 watts, which equals a bit less than 14 amps, so there is possibly a short. Howver, I do seem to remember that Lucas fuse ratings are not continuous i.e. a 35A fuse won't carry 35 A all the time. I really don't know it's continuous rating but I certainly would never fuse all the light circuits through one fuse, as a failure leaves you totally in the dark.
Alec
Thanks Alec
I understand your point about the load but surely the load from the lighting is the same whether the car is on tickover and stationary or if it is driving along. Also if there is a short wont it be there in both cases, the only variable is the energy being generated by the alternator
Dave
I understand your point about the load but surely the load from the lighting is the same whether the car is on tickover and stationary or if it is driving along. Also if there is a short wont it be there in both cases, the only variable is the energy being generated by the alternator
Dave
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Cam
- Moderator
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35amp blow, 17amp continuous.Howver, I do seem to remember that Lucas fuse ratings are not continuous i.e. a 35A fuse won't carry 35 A all the time. I really don't know it's continuous rating but I certainly would never fuse all the light circuits through one fuse, as a failure leaves you totally in the dark.
Sounds like you might have an intermittant short which is being 'activated' by the vibration of the road.
Websites: 
It gets worse!
Spent the afternoon going through the lighting circuit, speedo out checked switch checked wiring all round no apparent problems. Started engine with 35 amp fuse in place on blue brown lighting feed, runs well, put all lights , indicators and brake lights on revved engine all working fine, decided to go for test drive, reversed say 5 metres out of garage lights went out fuse blew, appeared to coincide with touching brakes. Decided that maybe the fuse was the problem so put lighting wire directly onto other "thick" wires without the fuse. Tried in garage all working fine, reversed out again with all lights on got about five metres again lights went off, grabbed blue brown lighting wire from connection box but not before it had starteds smoking.
Now feel problem is related to brakes , but doesnt seem to go when just pressing brake pedal in garage but now when there is no blue brown wire connected brake lights are working ok.
Checked all bullet connectors at front and rear lights and in boot, all seems ok
Any ideas out there??
Dave
Spent the afternoon going through the lighting circuit, speedo out checked switch checked wiring all round no apparent problems. Started engine with 35 amp fuse in place on blue brown lighting feed, runs well, put all lights , indicators and brake lights on revved engine all working fine, decided to go for test drive, reversed say 5 metres out of garage lights went out fuse blew, appeared to coincide with touching brakes. Decided that maybe the fuse was the problem so put lighting wire directly onto other "thick" wires without the fuse. Tried in garage all working fine, reversed out again with all lights on got about five metres again lights went off, grabbed blue brown lighting wire from connection box but not before it had starteds smoking.
Now feel problem is related to brakes , but doesnt seem to go when just pressing brake pedal in garage but now when there is no blue brown wire connected brake lights are working ok.
Checked all bullet connectors at front and rear lights and in boot, all seems ok
Any ideas out there??
Dave
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Pyoor_Kate
- Minor Addict
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- Location: Washington State, US.
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Assuming your looms not so badly damaged that you think it needs that secotion replacing.
Well, First, try and remedy the damage done by not having a fuse in....this will probably involve removing the covering from the loom as you may find that the wire's overheated somewhere else, lost it's insulation and melted into another wire. Repair any damage like this. Then, get yourself a fire extinguisher (suitable for use on Electical fires) a (decent size one).
*then*;
- Check for shorts in all the sections of the loom you can get to, Stick a brick on the brakes (or whatever it takes to get the lights on), check again. Disassemble the light holders, check for stray wires, check for separated lucar-connectors.
If that doesn't work...
- put a fuse in, go round wiggling chunks of the loom until you find the bit that makes the fuse blow.
Well, First, try and remedy the damage done by not having a fuse in....this will probably involve removing the covering from the loom as you may find that the wire's overheated somewhere else, lost it's insulation and melted into another wire. Repair any damage like this. Then, get yourself a fire extinguisher (suitable for use on Electical fires) a (decent size one).
*then*;
- Check for shorts in all the sections of the loom you can get to, Stick a brick on the brakes (or whatever it takes to get the lights on), check again. Disassemble the light holders, check for stray wires, check for separated lucar-connectors.
If that doesn't work...
- put a fuse in, go round wiggling chunks of the loom until you find the bit that makes the fuse blow.
Pyoor Kate
The Electric Minor Project
The Current Fleet:
1969 Morris 'thou, 4 Door. 2010 Mitsubishi iMiEV. 1920s BSA Pushbike. 1930s Raleigh pushbike.
The Ex-Fleet:
1974 & 1975 Daf 44s, 1975 Enfield 8000 EV, 1989 Yugo 45, 1981 Golf Mk1, 1971 Vauxhall Viva, 1989 MZ ETZ 125, 1989 Volvo Vario 340, 1990, 1996 & 1997 MZ/Kanuni ETZ 251s
Desires:
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The Electric Minor Project
The Current Fleet:
1969 Morris 'thou, 4 Door. 2010 Mitsubishi iMiEV. 1920s BSA Pushbike. 1930s Raleigh pushbike.
The Ex-Fleet:
1974 & 1975 Daf 44s, 1975 Enfield 8000 EV, 1989 Yugo 45, 1981 Golf Mk1, 1971 Vauxhall Viva, 1989 MZ ETZ 125, 1989 Volvo Vario 340, 1990, 1996 & 1997 MZ/Kanuni ETZ 251s
Desires:
Trabant 601, Tatra T603, Series II Landy, Moskvitch-401, Vincent HRD Black Shadow, Huge garage, Job in Washington State.
Have a look at the brake switch!
I had one that failed, it caused some hiss on the radio while it was poorly.
It's possible that it's shorting to earth ...
(mind you, that could be true of all the connectors, especially moving under braking. - check the usual suspects..)
It looks as if you're going to have to spend a fair bit of time with a multimeter and friend(s) turning everything on/off, waggling it etc.
In theory, the the system voltage is higher with the engine running (the dynamo/alternator has to produce more volts than the battery to charge the battery), but this should not be large enough to cause a significant increase in the current - maybe worth checking the voltage output from the alternator..
Colin
I had one that failed, it caused some hiss on the radio while it was poorly.
It's possible that it's shorting to earth ...
(mind you, that could be true of all the connectors, especially moving under braking. - check the usual suspects..)
It looks as if you're going to have to spend a fair bit of time with a multimeter and friend(s) turning everything on/off, waggling it etc.
In theory, the the system voltage is higher with the engine running (the dynamo/alternator has to produce more volts than the battery to charge the battery), but this should not be large enough to cause a significant increase in the current - maybe worth checking the voltage output from the alternator..
Colin
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Willie
- Minor Legend
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shorts
If you wish to prove if the fault is within the stop lights circuits then you need
to disconnect the Green/purple wire from the stop lamp switch(on the floor
to the left of the radiator). This lead supplies both rear stop lamps when it is
operated ,and, if the fault disappears with it disconnected I would suggest
that you start by checking where the wiring to the rear of the car passes
close to the clutch operating mechanism! It could be that there is chaffing
in that area which only shorts out when the brake pedal and the clutch pedal
are depressed??
to disconnect the Green/purple wire from the stop lamp switch(on the floor
to the left of the radiator). This lead supplies both rear stop lamps when it is
operated ,and, if the fault disappears with it disconnected I would suggest
that you start by checking where the wiring to the rear of the car passes
close to the clutch operating mechanism! It could be that there is chaffing
in that area which only shorts out when the brake pedal and the clutch pedal
are depressed??
Willie
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Alec
- Minor Legend
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- Location: Oswestry, Shropshire
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Hello Dave,
if the blue\brown lighting wire was smoking then the short is downstream of that circuit. This only feeds the headlights and the side tail lights but through a fuse so any problem downstream of the fuse would have blown that. No other circuit will cause the problem unless some modification has been done to the wiring and something else is tapped off the light circuit. I would check the dip switch first of all and look for damaged\frayed\loose connections\wire maybe even the switch itself.
Evidence of arcing in is quite distinctive and easily spotted. The less likely but possible is the side\headlight switch and also the loom from the bulkhead to the front of the car and across the radiator.
Alec
if the blue\brown lighting wire was smoking then the short is downstream of that circuit. This only feeds the headlights and the side tail lights but through a fuse so any problem downstream of the fuse would have blown that. No other circuit will cause the problem unless some modification has been done to the wiring and something else is tapped off the light circuit. I would check the dip switch first of all and look for damaged\frayed\loose connections\wire maybe even the switch itself.
Evidence of arcing in is quite distinctive and easily spotted. The less likely but possible is the side\headlight switch and also the loom from the bulkhead to the front of the car and across the radiator.
Alec
Progress report.
Checked loom at clutch pedal area but although it looked a potential pinch point there was no internal damage. So took out glove boxes and Speedo and found recent damage to cables to /from light switch. Checked blue cable to dip switch and all connections to dip switch intact and no signs of arcing but then having taken out the carpets there it was, the clamp bolt at bottom of steering column had been shorting onto cable running down steering column and feeding dip switch. So when I was in garage with wheels straight all worked perfectly but then when I reversed out and turned steering wheel the bolt head came round and shorted out.
So I have cut away about six inches of braiding from loom behind the dash and damage to blue cable seemsrestricted to that and adjacent cables in loom seem ok.
So I now need to rewire blue brown to feed on bulkhead and from my frogeye rebuild I remeber that AH Spares do a braided loom with same colours for dip switch for less that £5 so I can keep that tidy and avoid cutting any further into the main loom.
But thats for another day!
Checked loom at clutch pedal area but although it looked a potential pinch point there was no internal damage. So took out glove boxes and Speedo and found recent damage to cables to /from light switch. Checked blue cable to dip switch and all connections to dip switch intact and no signs of arcing but then having taken out the carpets there it was, the clamp bolt at bottom of steering column had been shorting onto cable running down steering column and feeding dip switch. So when I was in garage with wheels straight all worked perfectly but then when I reversed out and turned steering wheel the bolt head came round and shorted out.
So I have cut away about six inches of braiding from loom behind the dash and damage to blue cable seemsrestricted to that and adjacent cables in loom seem ok.
So I now need to rewire blue brown to feed on bulkhead and from my frogeye rebuild I remeber that AH Spares do a braided loom with same colours for dip switch for less that £5 so I can keep that tidy and avoid cutting any further into the main loom.
But thats for another day!
I don't have details. The switch was just one from my spares box, with the wires unplugged from foot switch and extended a few inches (I think) so I could mount the switch on a home made metal bracket to the LHS of the dash. Sorry not to be more help - I'll have a look at it tomorrow and see if I did anything else and take a photo.
Congrats on solving your problem, BTW!
Congrats on solving your problem, BTW!
