My 1990 V12 has been sat for some time. When I turn in the key I have no lights on the dash and the starter doesn't turn over I was about to go out and get a new battery and then I noticed that the red lights in the doors are on and stay on when I attempt to start so now I suspect a bad connection. Where to start looking though?

 

Test the doors by manually pushing the button in the door jam...? Is it the usual thing (I never noticed) that the door lights turn off and in at crank? I just tested, happen to be sitting in my 1990 conv, and the lights stay on and are independent of crank and continue to work on the timer...

I want to hear what others say but I might start by inspecting and cleaning up the contacts in the ignition key switch. Sounds like she ain't booting up at key turn - not sending power to individual systems and sending power to individual components. Will the radio come on in position 2 or 3 on the key? Trip computer, etc...?

 

Since its sat for a while, you have along tedious task.

There are EARTH connectors alongside the battery tray, a stupid double arrangement around the LH engine mount. Numerous others in mnay places.

The POWER side, has the 2 +ve posts in the engine bay, one near the trans dipstick, and the other mirrored on teh LH side. DO NOT drop those nuts, they are some weird Pommy thread.

In the MAIN battery +ve cable, there is a plastic cover over a connector junction., make sure they are attached and clean.

A GOOD healthy battery is paramount.

When you turn the key to Pos #2, (AKA Ign), you should hear the fuel pump buzz for 2 -3 seconds, this is important.

The list goes on, but that is the basics, and time consuming.

 

Yes, I am expecting a struggle.
The battery may be sub-optimal but if it has enough energy to power the door light brightly then the dash lights should also be on. Is there a relay that could be stuck?

 

James,

If it's been sitting for a while, and was running fine beforehand, there's naturally a chance that the battery's pretty flat. Before, you start checking anything else, I would just measure the voltage in the battery. Anything below about 12.3 and the car probably isn't going to start anyway. It doesn't take much residual current to power those door lights and they are not ignition controlled. So If the battery is low, charge the battery up, or hook up a booster charger or jump leads to another battery and then see what the ignition does.

Good luck

Paul

 

List of electrical stuff that works:

Interior boot light
Rear fog lights
Red door lights
Hazard Lights

That seems to be about it!

 

Battery is at 12.53V after being left overnight. I have had a booster pack and a 12A charger connected with no noticeable difference.

 

You have a bad connection(s) somewhere and as GF explained you have a bit of a chase ahead of you...
Enjoy it. Really. I spent days and days just poking around the car and slowly cleaning up contacts, fuses, grounds, relays etc. I learned a lot about the car, where things were and it always and only improves things. I still do this. And, because of the nature of the car it's ongoing. And, well, it's a 30yr old car and comes with the territory.

 

I realize that but I was hoping that there may be some common failure point. We currently have a couple of days of good weather so I am using my half-hour lunch breaks to try and get it up and running again.

 

The stuff Grant mentioned

The "+" junction posts on the firewall are the main trunks from which all the branches sprout, so to speak. It's plausible that a poor connection at one of the posts would leave some circuits dead while other worked perfectly well.

Cheers
DD

 

Apologies, James. I didn't mean to come off as smug and realized after your response that I was just stating the obvious... Good luck and I'll be looking forward to your progress,,, and there will be progress...!

 

I realize I don't have a v12, but the AJ16 engine would not start if I only had 12.5 volts at the battery. It doesn't like it when I have 13v! The power locks begin to fail at that point. 14.7 is what it likes to see.

That battery is suspect and if it only tops out at 12.5 after an overnight charge, then that battery has to be replaced regardless.

 

That is not a good battery. Connected to a battery charger should be more like 14V when charged up. When the battery charger is removed voltage will drop gradually to maybe 13V.

 

OK, coffee #6, and before the add ons take over.

Expose the Electrical section on the backside of the Ign Switch.

Get down and dirty in that "huge" space with a volt meter.

The BROWN wire is 12V HOT from the battery.
The WHITE wire is the IGN feed to the whole car.
Make sure you have battery volts in that BROWN wire, then switch to Pos#2, and ensure you have VERY CLOSE to battery volts in that WHITE wire,

If so, the electrical section of that switch is POSSIBLY OK. There is more testing, but with battery volts IN that WHITE wire in Pos#2 the Ign feed items should be active.

Relay, NO idea on a 1990.

Coupla Doco's to ponder.