rewiring the 240K

[Mat Big Hat]

slightly off-topic, but my car's got a bit of a power drain situation: whenever the brake lights or turnsignals go on, the headlights dim accordingly. troubleshooting ideas?

[aarc240]

slightly off-topic, but my car's got a bit of a power drain situation: whenever the brake lights or turn signals go on, the headlights dim accordingly. troubleshooting ideas?

Start by cleaning up every body earth point. As the brake lights are involved, pay particular attention to the rear light earths.

Unscrew each fastener, lift the terminal, scrape/sand body and terminal to bright metal, apply a thin smear of grease (copper base if you've got it but not critical) to both.

Remove all globes and clean. Check for corrosion inside the globe holder and if there is much carefully scrape/sand to bright metal and coat with a smear of grease.

You may need to clean each multi-way plug/socket too.

It's a peculiarity of early Datsun's that when earths are not really good you get some weird interaction which is most noticable in the headlights!

There could still be a real power drain so if earth cleanup doesn't fix it pull the globes from the rear lights and see if the headlights dim then.

[khughes]

thank you so much! that makes a lot of sense.

i just have to find the time to sort through the rather large box full of wiring now

[khughes]

oh man.. i have a massive mess of wires now! and just my luck, i can't find an R33 GTST full body wiring diagram anywere (engine diagrams are no problem).. i have a LOT of tracing and guessing to do.. i also don't have any body control modules etc. so not sure if that will affect me,

[aarc240]

OK, you have what you need in the R33 engine diag, the RB25DET (source car) engine diag and the C110 diag.

First off, in the body you only need to replicate the C110 plus any desired extras and with addition of any RB25DET related wiring you wish to make integral to the finished harness.

I wouldn't be inclined to do that myself, preferring to keep the engine to ECU harness with all sensor wiring etc as a completely seperate unit with ONLY the essential interconnections for 'ignition on' signal etc.

Have a browse on http://www.msefi.com/ forums for ideas on creating a good engine harness.

On the body side of things, make out a list of the 'extras' you want like driving lights, electric fuel pumps etc.

Work out how you need these to operate and where any interconnections need to be (electrically).

If you have a decent size shed floor to work on it will be easier to draw out the C110 profile full size.

Mark in the postions of components (fuse box, lights, pumps etc etc). At each position add info for distance above car floor.

Start laying out your colour coded wires on that 'plan' and you will be surprised how quickly you will see what is needed. Remember to allow for the height above your car floor reference plane - it's a three dimensional thing.

It's a good idea to leave extra wire at each termination point, that way you can tape the harness together at say 300mm intervals (and every branch point) and trial fit it in the car to determine just where you want to cut the wires.

While laying out the wires, use a photocopy of the source diagrams (enlarged if need be) and mark off each wire with a pencil as you do it.

With a first time harness, just break the job down into smaller chunks. Say the front light wiring as one task, the rear body wiring as another, etc.

When it all seems too hard, remember that people wire things like Space Shuttles successfully. And do ask for help.

[aarc240]

Some additional things to make life a bit easier.

For mounting 2 or 3 relays in some spot, get the mount plates, screws, relay bases and a chunk of harness from a junked 1985 onwards Ford Fairlane.

For relays in those, collect some from VL and later Commodores. The ones you want have the 'internals' diag molded into the side and on that diag you can see a small rectangular block in parallel to the coil. It's a 'snubber' resistor which suppresses the back EMF pulse which normally occurs when a relay switches off. Very good when ECU's get into the car!

Watch the terminal configuration - there are a few variants in those supposedly standard relays! It's a good idea to source the relays from one make & model but not always feasible. If any differences are necessary, document it in your own wiring manual for future reference.

If you solder any terminals, use heatshrink tubing for strain relief to at least 15mm down the wire. Otherwise you WILL get vibration breakage where the solder ends and plain copper strands start.

Make sure you source from the battery as direct as reasonably possible for electronics.

Use a common earth ('chassis') point for everything you can. Obviously front and rear lights etc don't have this but at each end of the car make a good solid connection to chassis and use it. Scraping a circular patch to bare metal and then 'tinning' that gives a good long term solution, but a clean bright patch of metal with a thin smear of grease is nearly as good. Any terminals bolted to either of those will make good connection.