SECONDARY FUSE BOARD AND RELAY PANEL
Sept 1, 2022 15:48:02 GMT
Phil Nottingham and tarnowl like this
Post by p5andrew on Sept 1, 2022 15:48:02 GMT
After continued problems with the original fuel pump and occasional fuel vaporisation issues, I decided to give in and install a Facet electric pump. However, I was not comfortable with the idea of an electric pump without also including an inertia cut-off switch; in my view this is an essential safety feature which shuts off power to the pump in the event of a serious accident. My car is fitted with Lumenition electronic ignition and I decided to take things one step further and design the system such that the inertia switch also shuts off power to the ignition system.
When I purchased my P5B it had already been fitted with a Kenlowe electric fan. The installation had not been particularly tidily done, there being a good many loose wires, and it always offended my eye. Those with OCD like me will know what I mean! So, I decided to redesign the fan electrics as part of the project.
The tendency for the toggle switch on the binnacle which controls the lights to overheat and fail is well-known. Although less common, the headlight switch on the steering column can also fail. A simple way of avoiding both problems is to install relays into the headlamp circuits and I know a good many owners have gone down this path. Doing this reduces the loads imposed upon the switches to extremely low levels and dramatically improves switch reliability.
Taking everything into account, I decided to design a secondary fuseboard/relay panel to combine all functions. Separate outputs would be required the for the fuel pump, electronic ignition, electric cooling fan, LH dip, RH dip, LH main beam, RH main beam. The board would be powered from a single source and fitted with a fuse and relay for each of the required outputs. On my car, the obvious place to install the board was the nearside inner wing, there being just enough space to install it alongside the power steering reservoir.
The best place to install an inertia switch is on a bulkhead and out of harms’ way and I installed mine between the heater and the main fuse board. The power input to the switch is taken from a spare terminal on the Ignition Control output on the main fuse board (right hand terminals as you look at the fuse board from the front of the vehicle are the outputs i.e. after the fuses). The output from the inertia switch is taken to the actuating coils of the relays which power the fuel pump and electronic ignition. This means that, when the ignition switch is in the “on” position, there is power to the inertia switch and from there to the fuel pump and electronic ignition. If the inertia switch actuates, for instance in a serious frontal impact, power is immediately cut to the pump and ignition regardless of whether the ignition switch is still in the on position. Resetting the inertia switch to restore power is a simple matter of pressing a button on the switch.
Both the headlamps and the electric fan have high power requirements. It follows that the power supply to the secondary board needs to be more than capable of coping with the maximum load which might be imposed. If the ammeter is to register the load correctly, it is also important that the supply for the secondary board is taken from the correct point in the vehicle electrical system. There is a busbar behind the instrument binnacle and above the steering column which on my car, and I guess all unmodified cars, has a spare terminal. However, it is worth noting that this terminal is ½” rather than the usual ¼” found elsewhere on the car. The size of the terminal is a major advantage as it means it is more than capable of coping with the total power demand imposed by the secondary board, though the spade connectors of the correct size are very expensive. The only downside of taking a feed from the busbar is that it is pretty inaccessible, especially if like me you have large hands and are built like a brick outhouse! I used a 10mm² cable for the feed to the panel, to which I soldered ½” spade connector. The cable is led out through one of the existing holes in the bulkhead to the engine bay and then passes behind the heater box and round to the new board location. Separate cables from the inertia switch to the board, and from the board to the ignition module on the offside inner wing, were routed on the same path. A further four cables were laid from the offside dip/main beam headlamp feeds and also the lamps themselves via the same route behind the heater and round to the new board. All cables were then bound together to form a mini loom.
The incoming 10mm² feed cable to the panel terminates at an 8mm insulated stud. Individual feeds are then taken from the stud to the fuses. Feeds are then taken from the fuses to the appropriate relays.
The original feeds to the headlamps were disconnected and used to power the actuating coils to the appropriate headlamp relays on the new board. The outputs from the switch contacts on the same relays were then connected to the headlamps. I took the opportunity to renew all the bullet connectors to the various headlamp connectors, most of the originals having become very tired and corroded.
For the sake of simplicity, all the relays I used have switch contacts rated at 32A which is more than sufficient to cope with any of the individual circuits. The relays are all of plug-in type for ease of replacement should that ever be required.
I have never fully trusted crimp connectors and I hate the look of them. I therefore soldered all spade, bullet and ring connectors to the various cables to and from the new panel to maximise reliability.
I made the backplate for the new panel from a piece of 2mm thick steel sheet to carry the various components. The piece of steel was repurposed from the rear cover plate to a dead 1950’s oscilloscope I had knocking about the place, hence the extraneous holes visible in one or two photo’s. The backplate was drilled to align with the centres of two of the top row of the offside front wing securing bolts. A further mounting hole was drilled at the bottom edge of the backplate and a corresponding hole drilled in the inner wing, this being necessary to provide a suitable degree of rigidity. The original wing securing bolts were replaced with longer items so that sufficient spare length was available to also secure the new board. Nuts, washers and spring washers were used to anchor the wing in place. The panel was then secured in place to the same bolts with further nuts, washers and spring washers.
All works well and it is pleasing to note that the headlamps are noticeably brighter.
Andrew Nicholson
August 2022
Pictures and schematic will follow if someone can tell me how to add them!
When I purchased my P5B it had already been fitted with a Kenlowe electric fan. The installation had not been particularly tidily done, there being a good many loose wires, and it always offended my eye. Those with OCD like me will know what I mean! So, I decided to redesign the fan electrics as part of the project.
The tendency for the toggle switch on the binnacle which controls the lights to overheat and fail is well-known. Although less common, the headlight switch on the steering column can also fail. A simple way of avoiding both problems is to install relays into the headlamp circuits and I know a good many owners have gone down this path. Doing this reduces the loads imposed upon the switches to extremely low levels and dramatically improves switch reliability.
Taking everything into account, I decided to design a secondary fuseboard/relay panel to combine all functions. Separate outputs would be required the for the fuel pump, electronic ignition, electric cooling fan, LH dip, RH dip, LH main beam, RH main beam. The board would be powered from a single source and fitted with a fuse and relay for each of the required outputs. On my car, the obvious place to install the board was the nearside inner wing, there being just enough space to install it alongside the power steering reservoir.
The best place to install an inertia switch is on a bulkhead and out of harms’ way and I installed mine between the heater and the main fuse board. The power input to the switch is taken from a spare terminal on the Ignition Control output on the main fuse board (right hand terminals as you look at the fuse board from the front of the vehicle are the outputs i.e. after the fuses). The output from the inertia switch is taken to the actuating coils of the relays which power the fuel pump and electronic ignition. This means that, when the ignition switch is in the “on” position, there is power to the inertia switch and from there to the fuel pump and electronic ignition. If the inertia switch actuates, for instance in a serious frontal impact, power is immediately cut to the pump and ignition regardless of whether the ignition switch is still in the on position. Resetting the inertia switch to restore power is a simple matter of pressing a button on the switch.
Both the headlamps and the electric fan have high power requirements. It follows that the power supply to the secondary board needs to be more than capable of coping with the maximum load which might be imposed. If the ammeter is to register the load correctly, it is also important that the supply for the secondary board is taken from the correct point in the vehicle electrical system. There is a busbar behind the instrument binnacle and above the steering column which on my car, and I guess all unmodified cars, has a spare terminal. However, it is worth noting that this terminal is ½” rather than the usual ¼” found elsewhere on the car. The size of the terminal is a major advantage as it means it is more than capable of coping with the total power demand imposed by the secondary board, though the spade connectors of the correct size are very expensive. The only downside of taking a feed from the busbar is that it is pretty inaccessible, especially if like me you have large hands and are built like a brick outhouse! I used a 10mm² cable for the feed to the panel, to which I soldered ½” spade connector. The cable is led out through one of the existing holes in the bulkhead to the engine bay and then passes behind the heater box and round to the new board location. Separate cables from the inertia switch to the board, and from the board to the ignition module on the offside inner wing, were routed on the same path. A further four cables were laid from the offside dip/main beam headlamp feeds and also the lamps themselves via the same route behind the heater and round to the new board. All cables were then bound together to form a mini loom.
The incoming 10mm² feed cable to the panel terminates at an 8mm insulated stud. Individual feeds are then taken from the stud to the fuses. Feeds are then taken from the fuses to the appropriate relays.
The original feeds to the headlamps were disconnected and used to power the actuating coils to the appropriate headlamp relays on the new board. The outputs from the switch contacts on the same relays were then connected to the headlamps. I took the opportunity to renew all the bullet connectors to the various headlamp connectors, most of the originals having become very tired and corroded.
For the sake of simplicity, all the relays I used have switch contacts rated at 32A which is more than sufficient to cope with any of the individual circuits. The relays are all of plug-in type for ease of replacement should that ever be required.
I have never fully trusted crimp connectors and I hate the look of them. I therefore soldered all spade, bullet and ring connectors to the various cables to and from the new panel to maximise reliability.
I made the backplate for the new panel from a piece of 2mm thick steel sheet to carry the various components. The piece of steel was repurposed from the rear cover plate to a dead 1950’s oscilloscope I had knocking about the place, hence the extraneous holes visible in one or two photo’s. The backplate was drilled to align with the centres of two of the top row of the offside front wing securing bolts. A further mounting hole was drilled at the bottom edge of the backplate and a corresponding hole drilled in the inner wing, this being necessary to provide a suitable degree of rigidity. The original wing securing bolts were replaced with longer items so that sufficient spare length was available to also secure the new board. Nuts, washers and spring washers were used to anchor the wing in place. The panel was then secured in place to the same bolts with further nuts, washers and spring washers.
All works well and it is pleasing to note that the headlamps are noticeably brighter.
Andrew Nicholson
August 2022
Pictures and schematic will follow if someone can tell me how to add them!
