Electrical anomaly

[Stagnator]

Hi All
My first post on the forum. I had a Stag some 25-30 years ago and sold it on, have now purchased another one, which I intend to work on over the winter months. Having got it home I have found an anomaly in the electrical system. I am a sparks by trade but just need to clarify the situation. The interior light switch is very untidy and their have been some electrical repairs completed. My issue is that a fuse listed as 'overdrive' (it's automatic) supplies power to the interior lights. The external lights are separate I presume. When I switch on the lights to the dipped position the ignition lights up. If I pull the overdrive fuse, which is a 25amp! I lose the interior lights but all external lights work.

I presume there is a short between the two somewhere, or some repairs made causing the issue. Has anyone come across this before? Does anyone have a fuse board diagram? And any pointers as to where to look first would help me solve this problem.

I have a '72 mk1

Thanks Everyone

[StagJonno]

From memory, I don't think the interior lighting is represented very well in the wiring diagrams of either the Repair & Operations Manual, or Haynes. Also, there are significant differences between Mk1 & Mk2 Stags. There's a schematic towards the end on the Grampian stag website:

http://www.grampianstags.net/SOC%20Reprints%20-%2013%20Electrical.pdf

Julian Leyton (a previous member) has posted a similar diagram on this forum in the past showing the results of his investigations (think I've got a copy somewhere). If you PM me with your email address, I'll copy across this and any other stuff that might be useful.

Jonno

[DJT]

Try this:

Interior Lighting.jpg

[brian0443]

There are wiring diagrams in the workshop manual, but black on white. I don't know who put in the time and effort to do this one, but thanks to whoever did it and shared it.

http://www.waghornswood.net.nz/Manua...ng_diagram.pdf

You will be referring to the purple area, bottom middle. Feed should normally be from first fuse in box which is not ignition controlled. The fact that someone switched it to the unused Overdrive fuse may be a pointer to your problems. Check whether power feed is ignition dependant.

Anyway.. 31 to 33 is horn, .... Oops Disregard reference to numbers. Replaced by labels in this later version.

Good luck
Brian

[brian0443]

A further consideration.
Please check your door switches. The originals do not run to earth but are isolated from the frame and have two wired connections. These switches were unavailable for a time and your wiring may have been altered to use the 'standard' one wire and earth connection.
Brian

[thebadleys]

This is the explanation that Julian Leyton wrote about the interior lights which Jonno mentioned.

Interior Lights - A Explanation.pdf

[StagJonno]

This is the explanation that Julian Leyton wrote about the interior lights which Jonno mentioned.

[ATTACH]42265[/ATTACH]

Thanks Nigel. Just back from a night out with friends, so nice to knock something of the tuit list

Jonno

[Stagnator]

Thank you all.

This will help me a lot, have a feeling I am going to be doing a lot of alterations on the wiring, am finding lots of little repairs, splices and addons as I look it over. I have one further question as I cannot seem to trace this on the schematic. The wiring to the starter motor has had an untidy repair and that is starting to fail. Sadly they have not put enough cable on the repair and it is under stress causing it to come off the spade connection. The cable is white with red strip and goes to the spade on the starter motor. There is also a thinner white and red one which has been crimped and left unused. Does anyone know if this should be connected as presuming it once was, and what to?

Many thanks

[StagJonno]

Strange. Firstly, I'd check, out on a clear road, that the inhibit switch on the Auto box hasn't been by-passed by trying to start in any position other than P or N. If it does, then needs sorting, pronto.

I've only got a Mk2 diagram to hand, but I think Mk1 & 2 are similar. The White/ Red comes from the IGN switch (start position) and goes to the Auto Box inhibit switch (I don't know the routing as mine is MOD, there may originally have been a connector close to the Starter to connect the Inhibitor in the loop). From there it goes to the Starter Solenoid. A second wire from the Solenoid, should be White/ Yellow, goes to either the coil or possibly the Ballast Resistor terminal that feeds the Coil. The Ballast on Mk1 is a chunky resistor in a ceramic former. It is connected in series with the coil, which was originally specified at 6V. For starting, the White/ Yellow wire bypasses the Ballast and puts a nominal 12V onto the coil to assist spark generation when the battery voltage is depressed by the load of the Starter Motor.

As the wiring to the Starter Solenoid has been repaired, the PO may have used a length of White/ Red to make all or part of the feed to the Coil/ Ballast.

It'd be worth checking around the Coil to see if you've got a Ballast Resistor, or if a PO might have swapped for a 12V Coil.

Note - for the Mk2, the ballast resistor was in the form of a resistive wire, colour coded Pink/ White, included in the loom. Also, take note that these Starter Solenoid and Coil circuits are not fused, so any shorts in them to the chassis etc will cause damage to the wires and their insulation and possibly a fire. For this reason, if you need to use your car before you can investigate, I'd recommend that you wrap some insulating tape around the "spare" White/ Red connector.

Jonno