Leaky electrics
Discussion
I decided to have a look into why my lights are so rubbish this evening. I've been thinking about putting a relay in for the lights but thought i'd check how many volts the bulbs were actually getting to see if the effort was worth it. So out with the multimeter and I see the bulbs are getting a grand total of...
...7 Volts!
Seeing as my battery was putting out 13 V the other 6 were leaking away somewhere! I have currently tracked down the little blighters to somewhere between the switch on the steering column and the lights themselves. I think I'm going to bypass the dim-dip relay and module to see if that helps then put a relay in for the dip and main beams. Hopefully that will transfer some energy from my warm wiring to the bulbs! Add on some Wipac crystal headlights and I think I might actually be able to see at night
During my rummaging I also found that a previous owner had removed the ignition fuse from the fuse holder and wired it in behind the fuse box where it had merrily melted!
It seems that one arm had got so corroded that the resistance on the connection had got high enough to melt the fuse. I measured the resistance at over 2 Ohms which would explain it! Slightly worrying that was happily heating up and melting away under the dash for god knows how long.
I replaced it with a new fuse and connectors but I think it shocked the ECU having the full voltage available, the car was idling at about 1300RPM when I started it. An hour long drive to the supermarket 4 miles away sorted that out though
Hopefully I'll be able to let you know how I managed to quadruple the light output of my headlights soon!
...7 Volts!
Seeing as my battery was putting out 13 V the other 6 were leaking away somewhere! I have currently tracked down the little blighters to somewhere between the switch on the steering column and the lights themselves. I think I'm going to bypass the dim-dip relay and module to see if that helps then put a relay in for the dip and main beams. Hopefully that will transfer some energy from my warm wiring to the bulbs! Add on some Wipac crystal headlights and I think I might actually be able to see at night
During my rummaging I also found that a previous owner had removed the ignition fuse from the fuse holder and wired it in behind the fuse box where it had merrily melted!
It seems that one arm had got so corroded that the resistance on the connection had got high enough to melt the fuse. I measured the resistance at over 2 Ohms which would explain it! Slightly worrying that was happily heating up and melting away under the dash for god knows how long.
I replaced it with a new fuse and connectors but I think it shocked the ECU having the full voltage available, the car was idling at about 1300RPM when I started it. An hour long drive to the supermarket 4 miles away sorted that out though
Hopefully I'll be able to let you know how I managed to quadruple the light output of my headlights soon!
Was the engine running when you checked and found 7 volts? Some cars knock down the voltage on just ignition to avoid draining the batt. Wouldn't expect it as low as 7v mind you.... But it's likely to be something simple anyway as we all know electricity doesn't leak. Unless there's something in to knock it down or some other reason for the volt drop.. Such as resistance/dirty/dodgy connection.
The S doesn't have anything fancy like that...well at least there isn't anything on the wiring diagram!
I didn't check with the engine on as my neighbours get stroppy with me for having the car running on the drive, apparently it's too noisy
I didn't really want to let it warm up to blip it and get the alternator charging then check the lights. Would have put me in the dog house!
I didn't check with the engine on as my neighbours get stroppy with me for having the car running on the drive, apparently it's too noisy
I didn't really want to let it warm up to blip it and get the alternator charging then check the lights. Would have put me in the dog house!
Yazza54 said:
Wouldn't expect it as low as 7v mind you.... But it's likely to be something simple anyway as we all know electricity doesn't leak.
Electricity doesn't leak? So where does the smoke come from? Reminded me of good old Joe Lucas, Prince of Darkness...
http://www.peizhang.com/forfun/forfun_writings_smo...
...Yes ... I said you must have a resistance to drop the volts... The volts don't just bloody leak into the atmosphere!
The only reason a cable should overheat is if it's carrying too much current for it's size or it's in a much hotter atmosphere than designed for/grouped with a load of other hot cables.
The only reason a cable should overheat is if it's carrying too much current for it's size or it's in a much hotter atmosphere than designed for/grouped with a load of other hot cables.
k this I'm going to make some tyre smoke in the fury. Yazza, sorry my first post was a light hearted and jokey way of saying that the reason my lights are so dim is because my 22 year old TVR electrics are decidedly dodgy!
I know the volts don't just leak away but the resistance of the lighting circuit was causing a significant amount of power to be lost. I was being facetious about it and didn't really explain that to you at the beginning of this thread! Didn't help the others got involved with wires 'leaking' smoke!
I know the volts don't just leak away but the resistance of the lighting circuit was causing a significant amount of power to be lost. I was being facetious about it and didn't really explain that to you at the beginning of this thread! Didn't help the others got involved with wires 'leaking' smoke!
Anyway back to the topic...
I found that the 30A fuse in the circuit had partially melted too which explains why the fuse box was so warm when I felt it last night after my drive. After replacing that fuse, cleaning the other 2 fuses and the Dim Dip relay contacts I now have 9V at the lights! They are now painful to look at when I measure the voltage across the bulb rather than just a little bright.
Today I characterised the entire system by connecting one end of the multimeter up to the battery +ve then measuring the Voltage at each point along the circuit to see where the biggest drops were. I'm sure this isn't useful to anyone but me but here are my results:
Helpfully the wire with the biggest drop goes behind the dash which I refuse to take out!!
I found that the 30A fuse in the circuit had partially melted too which explains why the fuse box was so warm when I felt it last night after my drive. After replacing that fuse, cleaning the other 2 fuses and the Dim Dip relay contacts I now have 9V at the lights! They are now painful to look at when I measure the voltage across the bulb rather than just a little bright.
Today I characterised the entire system by connecting one end of the multimeter up to the battery +ve then measuring the Voltage at each point along the circuit to see where the biggest drops were. I'm sure this isn't useful to anyone but me but here are my results:
| Measurement point | Side | V Indicated | Difference |
|---|---|---|---|
| 30A fuse | +ve | 0.57V | |
| -ve | 0.59V | 0.02V | |
| Side/Dip/Off switch | +ve | 0.79V | 0.20V |
| -ve | 0.95V | 0.16V | |
| Dip/Main/Flash switch | +ve | 1.41V | 0.46V |
| -ve | 1.68V | 0.27V | |
| Dim Dip Relay | +ve | 2.30V | 0.62V |
| -ve | 2.32V | 0.02V | |
| 15A fuse | +ve | 2.32V | 0.00V |
| -ve | 2.38V | 0.06V | |
| Bulb | +ve | 2.77V | 0.39V |
| -ve | 11.77V | 9.00V | |
| Battery | -ve | 12.10V | 0.43V |
Helpfully the wire with the biggest drop goes behind the dash which I refuse to take out!!
Edited by orange_dodo on Saturday 16th April 14:04
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