Richardtr3a Posted October 4, 2017 Report Share Posted October 4, 2017 I had some problems fitting my heater back in behind the dashboard after cleaning it up and repairing the battery box. It was very difficult to lift into place. I had to use a short length of timber and squeezed it in finally. Some months later I discovered that the engine would not switch off when the side and headlights were on. I assumed that the compressed wiring behind the dash was responsible. So I was able to live with that for a while and plan to lift out the instrument panel on a warm day this autumn and check all the connections However on my return from our SDG Autumn run this week-end I tried turning off the ignition using the key, while the car was still moving on the open road, and it cut off the ignition instantly. So when stationary with the lights on there is a rogue electrical supply to the ignition and when moving with the lights on the rogue supply is off. Is there any one available to help with an answer? Thanks Richard & H. Quote Link to post Share on other sites
TomMull Posted October 4, 2017 Report Share Posted October 4, 2017 My first guess and I emphasize guess would be a missing or loose ground on the panel. I have absolutely no idea why moving or stopped would make a difference unless of course your foot was on the brake when stopped. Tom Quote Link to post Share on other sites
Dave Larnder Posted October 4, 2017 Report Share Posted October 4, 2017 Richard When you finally find the source of your problem, consider installing relays and an 8 way fuse box in your car. I have fitted four in my TR3A, one for lights, second for horns, third for Alternator and fourth for Kenlowe fan. One thing I do know is that the lights are so much brighter since fitting the relay. BTW I owe my thanks to IAN C and his friend for the extra wiring diagram to suit these relays, so if you need it, and they have no objections to me passing it on, I will e mail it to you when I get home in 7 days time. P.M. me your e mail address if you go that way. Dave Quote Link to post Share on other sites
MikeF Posted October 4, 2017 Report Share Posted October 4, 2017 My first guess and I emphasize guess would be a missing or loose ground on the panel. I have absolutely no idea why moving or stopped would make a difference unless of course your foot was on the brake when stopped. Tom Agreed. Most electrical faults are bad earths and this sounds like a classic one. The wiring on our cars is not particularly complex but there is enough to provide alternate pathways if you have a mix of poor and good connections to cause your volts to find an alternate lower resistance pathway. You can either spend a lot of time fault finding for the intellectual satisfaction of knowing which ones. Or spend the same or less time just cleaning up all your earth points. Start with affected circuits obviously. MIke Quote Link to post Share on other sites
Richardtr3a Posted October 5, 2017 Author Report Share Posted October 5, 2017 (edited) Checked it out on a short run this evening. When it was cold it all worked well and normal. But arriving back at home. the same problem cropped up. How can a warmed up engine make a difference? Week end for heater out after the classic car run in Uckfield on Saturday. Edited October 5, 2017 by Richardtr3a Quote Link to post Share on other sites
Richardtr3a Posted October 7, 2017 Author Report Share Posted October 7, 2017 Incorrect assessment by the owner. I have discovered that it is nothing to do with the engine running. When stationary I have my foot on the brakes. So I rewired the brake light switch to the main loom with a short length of cable and new connections and cleaned up the brake light switch. After some experimenting it seems as though the green/purple cable is the fault. If it is disconnected the problem has gone. When connected the engine will not switch off with the brake pedal depressed. The cable, 22 on the wiring diagram, only runs to the rear lights. The indicators have been running faster recently so there may be something affecting both circuits. I will have to clean up the earths on the lights and look for any damaged cable. This may lead me back to the dashboard switch Any further advice would be very useful. Thanks Richard & H. ( who is attending Saltdean Lido open air pool dog day tomorrow.) Quote Link to post Share on other sites
RogerH Posted October 7, 2017 Report Share Posted October 7, 2017 Hi Richard, have a look at your fuse box the White ignition feed cable and the Green cable to the brake switch are connected together there. Give it a good clean. Roger Quote Link to post Share on other sites
Richardtr3a Posted October 11, 2017 Author Report Share Posted October 11, 2017 Thanks for the tip Roger. I checked the fuse box and all looked fine.There were no loose or damaged cables. So I took out the cables at 2 x A4 and cleaned up all the wires and contacts. I tested the ignition switch with the engine running and it worked well with or without the brake light switch activated. I polished the connecting strip and sprayed connection cleaner in the thread before fitting the screws back in. This evening I cleaned up A3 as well. All is now back to normal but it is not clear what the defect can have been. Well done Roger Richard & h. Quote Link to post Share on other sites
Richardtr3a Posted October 20, 2017 Author Report Share Posted October 20, 2017 More progress. I have been fitting new earth connections to the rear lamps. Now it is darker in the evenings I was able to spot that the front side lights come on when you press the brake pedal. After a lot of dismantling I found that the rear left hand bulb was lighting up on both filaments which ever supply was connected. So I assumed that when pressing the brakes and sending current to the brake filament I am therefore sending current to the sidelight circuit. I changed the bulb and all lights are working properly. The ignition will now switch of with the side lights on and the brake light activated. I have not yet found out how the lights affect the ignition. Does any one have any ideas? Thanks Richard & H. Quote Link to post Share on other sites
RogerH Posted October 20, 2017 Report Share Posted October 20, 2017 Hi Richard, if the brake light is passing current to the side lights this would be fed back to the light switch and in turn feed contact A1 on the regulator box. I don't know what goes on in the Reg Box but this may feed to the Ig circuit. http://www.advanceautowire.com/tr24a.pdf Roger Quote Link to post Share on other sites
billy l Posted October 21, 2017 Report Share Posted October 21, 2017 With a dodgy bulb, power comes from the side lights through the dodgy bulb into the brake light circuit up to the brake light switch and via the switch into the ignition circuit keeping the engine running even when switched off, assuming the brake pedal is kept depressed?. I had this happen on an old vauxhall I used to look after for an old chap, I was scratching my head for a while until he told me he had recently changed a stop and tail bulb. Cheers, Bill. Quote Link to post Share on other sites
barkerwilliams Posted October 21, 2017 Report Share Posted October 21, 2017 Richard, Have you fitted a relay to control the ignition circuit? If so the limited current draw to hold a relay is provided by the ignition lamp circuit. A simple test if the ignition is running on with the ignition off is to turn on either the cabin heater fan or the wipers. If the engine stops instantly then the (brown white?) wire from the alternator needs a diode to prevent the limited current flow through the ignition lamp keeping the relay energised. This was an issue that Morten and I both experienced with an ignition relay. Alan Quote Link to post Share on other sites
ijonsson Posted October 21, 2017 Report Share Posted October 21, 2017 (edited) Richard, Have you fitted a relay to control the ignition circuit? If so the limited current draw to hold a relay is provided by the ignition lamp circuit. A simple test if the ignition is running on with the ignition off is to turn on either the cabin heater fan or the wipers. If the engine stops instantly then the (brown white?) wire from the alternator needs a diode to prevent the limited current flow through the ignition lamp keeping the relay energised. This was an issue that Morten and I both experienced with an ignition relay. Alan Ahhh, this explains it! I can't turn of the engine with ignition key, but it isn't a problem because I have a "hidden anti-theft" kill switch in the wire to the coil. Out looking for a diode then http://www.ijonsson.se/tr2/photos/el/wiring_mod.jpg EDIT: No diode in the shelf, would changing to a LED lamp instead of an ordinary filament bulb for ignition lamp work as well? Edited October 21, 2017 by ijonsson Quote Link to post Share on other sites
Lebro Posted October 21, 2017 Report Share Posted October 21, 2017 Richard. You "problem bulb" is a bad earth on either the bulb holder or the lamp unit to chassis. Bob. Quote Link to post Share on other sites
Richardtr3a Posted October 21, 2017 Author Report Share Posted October 21, 2017 Hi Bob I am very careful with earth connections and have fitted a number of extra points. The engine has one on each side and there are a number behind the dash connected to one place on the heater support. Each back light has a single earth. But they do need cleaning a lot, and my car does not get wet often but there is still corrosion. When I had the lamp in my hand and touched the earth to the body and a live feed to either terminal both filaments would light up. I replaced the lamp in the light base with a spare and it worked properly immediately. The chrome edge is worn so I have ordered a new unit and hope that it will be better made than my existing one. I was about 1/2 an hour away from calling out a specialist old car electrician I am sure that he would have found it much quicker than me. Roger, Thanks for the wiring diagram I have had it printed on heavy paper and it is easy to read. Quote Link to post Share on other sites
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