Euro spec carb 1500 (late) car.
After some success fitting the Panda light switch and 4-relay set up and putting a relay in to the electric fuel pump circuit (instead of the mechanical pump), I had a failure relating to the fitting of an ignition relay, with which I’d like some help. I wanted to take yet more stress off the ignition switch that I had just rebuilt.
By way of clarification, I adapted a simple ignition relay scheme to suit what I had available, what was easily accessible and the space available in the fusebox, (which means that I was not necessarily able to use the proper polarity connection scheme for the relay). Therefore:
Terminal 87 is fed by +12v from the busbar in the fusebox as the permanent live;
Terminal 30 then feeds +12v to the terminal on the rear of the fuseblock, (which was formerly occupied by the red/black wire which goes to the ignition switch (see below)) which connects internally in the fuseblock to the +12v wire to the coil (pink, if I recall correctly)
Terminal 86 (the control feed) is fed by the red/black wire from the ignition switch which has been disconnected from the fuseblock (see above). However, I see that this red/black wire has a back-feed from the alternator blue/black wire splice…
Terminal 85 is the earth wire to a convenient bolt on the dash underside (there is no earth-terminal rosette on this side of the car)
The engine started very well and idled for 10 minutes. At this point I thought I’d switch off and turned the key off. ………Engine continued to run with key OFF!
The easy way to stop the car was to take the main coil +12v feed from the coil.
I took the 5 pin ignition relay, which I had fitted, out of its holder and tested the female sockets:
12v is present at the high current feed with the ignition OFF as I expected, because it is straight off the battery +12v bus bar in the fusebox.
However still with the ignition OFF there was 0.6v at the low current control feed from the ignition switch; I was expecting 0v. I am wondering if that small voltage, indicating an unexpected current, is sufficient (when the engine is running and at a higher voltage from the alternator) to stop the relay unlatching and thereby allowing the current to the coil so that the engine carries on. The relay tests ok on the bench.
Looking at the ignition switch, the pigtails directly out of the switch ARE separate (there is no red/black wire there) but then those short pigtails go to a connector. At that connector (ie on the fusebox side of it), the blue/black wire to the ignition light and the red/black wire to the fuse block are connected. Hence there is effectively a feed from the alternator down the red/black wire (which I am using as the control wire for the relay) which I believe is causing the relay not to de-latch. The de-latch or drop out voltage of the relay was 2.7v on the bench (another one I tried was 3.9v) however.
I looked at the wiring diagram later and it seems that the control feed from the ignition switch is indeed spliced into the alternator-to-ignition light wire (blue/black at the ignition switch connector). So, I surmise that even though the ignition switch is turned off, whilst the engine “runs on”, the alternator is still pushing a voltage of at least 2.7v in the opposite direction.. As I say, that residual voltage seems to be enough to stop the de-latching or “dropping out” and the engine continues to run.
I wondered about fitting a diode enabled relay ie with the diode in the opposite direction to the alternator’s current BUT then surely I lose the ignition light? Which I do not want to do.
I want to keep the ignition relay add-on circuit within the fusebox and not run wires to the switch or take the switch apart again and separate terminals where etc.
Can anyone please explain what they used for a control feed for the ignition relay that does not allow the engine to “run on” but does keep the functionality of the ignition light and is a simple install. In other words how did you set up the ignition relay?
Thanks in advance.
RDS
After some success fitting the Panda light switch and 4-relay set up and putting a relay in to the electric fuel pump circuit (instead of the mechanical pump), I had a failure relating to the fitting of an ignition relay, with which I’d like some help. I wanted to take yet more stress off the ignition switch that I had just rebuilt.
By way of clarification, I adapted a simple ignition relay scheme to suit what I had available, what was easily accessible and the space available in the fusebox, (which means that I was not necessarily able to use the proper polarity connection scheme for the relay). Therefore:
Terminal 87 is fed by +12v from the busbar in the fusebox as the permanent live;
Terminal 30 then feeds +12v to the terminal on the rear of the fuseblock, (which was formerly occupied by the red/black wire which goes to the ignition switch (see below)) which connects internally in the fuseblock to the +12v wire to the coil (pink, if I recall correctly)
Terminal 86 (the control feed) is fed by the red/black wire from the ignition switch which has been disconnected from the fuseblock (see above). However, I see that this red/black wire has a back-feed from the alternator blue/black wire splice…
Terminal 85 is the earth wire to a convenient bolt on the dash underside (there is no earth-terminal rosette on this side of the car)
The engine started very well and idled for 10 minutes. At this point I thought I’d switch off and turned the key off. ………Engine continued to run with key OFF!
The easy way to stop the car was to take the main coil +12v feed from the coil.
I took the 5 pin ignition relay, which I had fitted, out of its holder and tested the female sockets:
12v is present at the high current feed with the ignition OFF as I expected, because it is straight off the battery +12v bus bar in the fusebox.
However still with the ignition OFF there was 0.6v at the low current control feed from the ignition switch; I was expecting 0v. I am wondering if that small voltage, indicating an unexpected current, is sufficient (when the engine is running and at a higher voltage from the alternator) to stop the relay unlatching and thereby allowing the current to the coil so that the engine carries on. The relay tests ok on the bench.
Looking at the ignition switch, the pigtails directly out of the switch ARE separate (there is no red/black wire there) but then those short pigtails go to a connector. At that connector (ie on the fusebox side of it), the blue/black wire to the ignition light and the red/black wire to the fuse block are connected. Hence there is effectively a feed from the alternator down the red/black wire (which I am using as the control wire for the relay) which I believe is causing the relay not to de-latch. The de-latch or drop out voltage of the relay was 2.7v on the bench (another one I tried was 3.9v) however.
I looked at the wiring diagram later and it seems that the control feed from the ignition switch is indeed spliced into the alternator-to-ignition light wire (blue/black at the ignition switch connector). So, I surmise that even though the ignition switch is turned off, whilst the engine “runs on”, the alternator is still pushing a voltage of at least 2.7v in the opposite direction.. As I say, that residual voltage seems to be enough to stop the de-latching or “dropping out” and the engine continues to run.
I wondered about fitting a diode enabled relay ie with the diode in the opposite direction to the alternator’s current BUT then surely I lose the ignition light? Which I do not want to do.
I want to keep the ignition relay add-on circuit within the fusebox and not run wires to the switch or take the switch apart again and separate terminals where etc.
Can anyone please explain what they used for a control feed for the ignition relay that does not allow the engine to “run on” but does keep the functionality of the ignition light and is a simple install. In other words how did you set up the ignition relay?
Thanks in advance.
RDS