The mysteries of Lucas - help

[JPSmit]

I'm trying to get at the last of my electrical stuff before I start putting things like <span style="text-decoration: line-through">hoods</span> bonnets on. Anyway, previously, when I hooked up the brake pressure failure switch, somehow current was leaking through such that the starter would not shut off but would keep turning the engine - even with the key removed. I thought it was the diodes - disconnected the ones I could see tonight and no change. So, electrical heads, I need your help.

The easiest way is to look at one of the manuals so,
If you have the 1500 Bentley manual, I am looking at the diagram on page 330. The brake switch is #27. The diodes in question are numbers 8, 9, and 10 respectively. These seem to me to be the only way the power could be leaking. I found and disconnected the diode at #8 and #10. I cannot locate the diode #9 under the dash.

If you have the Haynes Manual, it is page 207. (which is 1978 Midgets I know - but it seems right) Here the brake switch is #29 and the diodes 9 and 10 respectively with a "phantom" diode "penciled in" above #9. Again, it is this one that I cannot find. (BTW - to help you find it, it is in the upper right corner in both diagrams)

I don't know if this matters, but, the brake pressure failure switch and the reverse light run off the same part of the wire harness. Neither were getting power, so, rather than rip the whole section of harness apart to find the short, I tapped into the green feed line at the Stop Lamp Switch (#3 in both). Also, the handbrake warning light is not hooked up.

I know I really don't need to hook this up at all but I want it to be right.

Any suggestions gratefully received.

 

[RickB]

JP, sorry no specific help here but some general advice.
Try to simplify this as much as you can.
Whenever I hit a huge electrical challenge it helps me to somehow eliminate as much as possible from the situation. That way chasing after the rabbits that hop from circuit to circuit is kept to a minimum.
Sorry I can't offer any more than that at the moment.

 

[Morris]

JP,

What is your goal? Is it just to stop the current leakage, or do you wish to come out the other side with a functional brake warning light as it came from the factory?

I was able to fix the problem on my car such that the brake warning light still comes on when the parking brake is engaged, but the switch on the brake lines is not connected, and I disconnected on wire to my ignition switch. My reverse lights work fine... but didn't you delete your reverse lights?

 

[JPSmit]

JP,

What is your goal?

<span style="font-style: italic">I think I'd like the functioning light - more because I don't want a dangling wire in the engine bay and I don't really want to cut it</span>

and I disconnected on wire to my ignition switch.

<span style="font-style: italic">not sure I understand this - typo? And yes, I deleted the factory reverse light but reinstalled a reverse light - so I do still have one - under bumper</span>

 

[Morris]

Sorry for the typo. I was working late. I meant so say that I cut a wire in the harness that leads to my ignition switch. I have the connector to the brake failure switch inconspicuously zip stripped to the brake line awaiting a more permanent solution. I plan to remove my dash in a few weeks so that I can begin addressing all these fun little wiring projects.

Have you checked to see if you have 12v going to the brake switch terminal after disconnecting the wires you mentioned above? If there is not power there, you should be able to reconnect that terminal without issue.