| Author |  Topic  | |
andydeans3
V4 Guru
United Kingdom
2016 Posts |  Posted - 06 May 2018 : 23:57:00  
| A friend of mine's 70s classic recently had an electrical problem while driving, smoke coming from under the dash. By the time he'd stopped the car, gotten into the battery to disconnect it, the loom behind the dash was smoked. He could have lost the car.
This got me thinking.
I have a battery isolater on the negative battery terminal, but am wondering now if I should have some sort of isolation switch in the cab, that's accessible from the drivers seat.
Has anyone fitted such a switch?
If so, did you route the main battery earth line through the switch, or just the main grey feed line that goes from the alternator up to the fuse box?
Where did you mount the switch?
Any thoughts would be appreciated.
Andy
1978 LHD SAAB 96
1978 MGB Roadster
2008 LHD "Classic" Renault Twingo
1991 Nissan Figaro |
Edited by - andydeans3 on 07 May 2018 00:34:44 |
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TomS
Starting Member
United Kingdom
32 Posts | Posted - 10 May 2018 : 23:01:22
| | Andy, I would fit an isolator cut out switch of the sort that is mandatory on competition cars. They are operated by a large removal red key so a good anti theft device as well. If mounted under the dash the main battery lead to the starter would have to be brought in and broken at the switch, plus the feed wire to the coil and the wire to the alternator which is wired through the switch and to ground via a resistance that is supplied with the switch. Operating the switch isolates all the electrics and stops the engine instantly. |  |
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andydeans3
V4 Guru
United Kingdom
2016 Posts | Posted - 11 May 2018 : 12:30:47
| TomS
Not sure I'd like to bring that circa 100 amp battery to starter cable into the car....
If I smelled smoke, I'd immediately cut the ignition, but would then want to cut all the power to the system.
If I'm not mistaken this could be achieved by putting a switch into either the cable that runs from the starting motor, to the alternator, or the alternator to the top of the "Always live" block on the fuse box. ( 4mm2 grey cable). All ignition controlled circuits take their power from that point.
Andy
1978 LHD SAAB 96
1978 MGB Roadster
2008 LHD "Classic" Renault Twingo
1991 Nissan Figaro | |
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TomS
Starting Member
United Kingdom
32 Posts | Posted - 14 May 2018 : 07:49:30
| | Hi Andy It is mandatory on competition cars to break the main battery to starter cable so the switches are made to cope, another way would be so site the switch under the bonnet and operate it by a pull cable from inside the car. I think they earth the alternator wire through a resistance to prevent a power surge when the feed is cut damaging the diodes. There is an electrically operated remote cut out switch available but they are much more expensive then the manual type.All these are available from the specialist motorsport suppliers Demon Tweeks etc. | |
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andydeans3
V4 Guru
United Kingdom
2016 Posts | Posted - 19 May 2018 : 17:51:52
| Tom
We're not talking about competition situations here, just want to be able to cut power to the whole system, by flicking some sort of switch that can be reached from the driver's seat.
While this can obviously be achieved by bring the battery main power feed cable into the car, and feeding it through a suitably rated switch, I was hoping to achieve this without bring that heavy duty cable into the car.
I'll fit a switch between the heavy grey cable that feeds power from the alternator, up to terminals 1 to 4 on the fusebox.
Andy
1978 LHD SAAB 96
1978 MGB Roadster
2008 LHD "Classic" Renault Twingo
1991 Nissan Figaro | |
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TomS
Starting Member
United Kingdom
32 Posts | Posted - 21 May 2018 : 14:39:51
| | Hi Andy I have used a company called PoleVolt Ltd, they supply a huge range of auto electrical parts from cable to terminals all by very prompt mail order, might be worth checking their website for the switch etc. you will need. | |
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| | Topic | |
Fitting a power Isolation switch on a 96?
