Alternator issues (I think...)

Hi @Hicap phill, I'm not sure I understand what you mean. To clarify wot I wrote: I found the green wire coming out of the bunch of wires in 'loom' from the alternator and it had nothing on the end of it. There was a spade terminal with a connector attached with no wire attached to the connector and it looked like the green wire had, at some point in the past, been connected to the connector. Sorry, too many connection/connectors in that sentence). So I bared the green wire and joined it to the connector then reconnected it to the pressure switch and the light stays on permanently. Grateful if you will please clarify what you mean to this novice (relatively speaking).

Thanks
spins

Ok with all the connectors I got mixed up.
Please ignore me

Find your oil pressure switch, pull off the cable if there is one, then using your meter, 1 lead to battery positive and the other to the ps terminal. Should show voltage ,
If it does not show voltage, switch has failed open circuit.
If it does show voltage, start the engine and volt reading should drop to near zero, if it doesn't ,switch has failed closed circuit or your engine has problems.
I think that's correct anyway, but try a new switch before condemning the engine.

Thanks both.

@Flossie, not about to condemn engine, Tonk maybe halfway to a telegram form the Queen but she's only done a genuine 88k and the mechanicals all sound pretty good, not just for 50 but pretty good all round. I'll certainly try checking the voltages: a new 'switch' isn't particularly expensive and if it isn't the switch, I'll have lost about £5, and if it is the switch, I've saved a lot of blood, swearing and tears. And money.

spins

If you pull the green wire off the oil switch, the oil lamp should go out The oil switch just provides a path to ground for the bulb while engine off, once the engine is running, the oil pressure should build and open the switch and thus lamp should go out. therefore check first it does with wire off. If its stays on, then the green wire must have a short to ground somewhere on its run back to the dash

It’s a Witch. Burn it.

I had a similar issue on my S3 Lightweight, battery not charging, and I read about the charging light being in the circuit, and if bulb is duff you won't charge. So I removed the instrument panel cleaned up wires and gave them all a wiggle and hey presto, I'm getting 14.2v when running now. I can even use the wipers, lights AND heater at the same time! Also on lucas.

Worked for me.

Good point. I replaced my charging bulb with an LED then found i had no alternator output. The alternator relies on the current through the charging light bulb to energise the coils so the circuit is from the ign through the bulb to the alternator, once the alterntor energises the voltage comes up and the bulb goes out as it has the same voltage both sides.

Well, I is real confused now. What I thought was oil pressure switch, isn't. it's some sort of coolant thermometer; when I took it out clear water come pouring out, not oils but when I connected the stray green cable, it light up the oil pressure, green, light. I'm going to take pictures and post them here. Hopefully someone can point me in the right direction.

Thanks
spins

spins said:

Well, I is real confused now. What I thought was oil pressure switch, isn't. it's some sort of coolant thermometer; when I took it out clear water come pouring out, not oils but when I connected the stray green cable, it light up the oil pressure, green, light. I'm going to take pictures and post them here. Hopefully someone can point me in the right direction.

Thanks
spins

Click to expand...

The coolant sensor sits in side of the head next to the thermostat and hose. The gauge in dash feeds a voltage via a voltage regulator of about 9 volts to ensure constant voltage through a coil that heats up the more current flows . This connected to the negative side via the sensor in the block. When cold there is very little if any current flow due to high resistance, just same as pulling off the wire. But as the temperature rises, the resistance drops on the sensor and more current flows through the temperature instrument readout causing the needle to move towards the red.

There is no connection to charge lights or oil pressure, other than the pressure switch provides a ground connection to make the lamps light up. The oil switch looks like a mushroom about 2 pence size screwed into the block near the oil filter. Strange electrical faults are usually indication of poor ground to negative somewhere causing back feeds But first check the oil lamp wire is plugged into the switch

fsmr said:

Strange electrical faults are usually indication of poor ground to negative somewhere causing back feeds

Click to expand...

Thanks fsmr, having been at my local LR spares place yesterday morning I met a chap with a 1959 Ser 2 and we were discussing the issues and he said pretty much what you've said. The oldies mine is 1968 vintage suffer from dodgy earth problems and going back to my original issue, the alternator, I fitted a new plug to the back of it with the wires bared and reconnected but noticed that all three wires as far as the first clamp, just by the fan belt tensioning bolt, were cracked and bared in various places, hidden by insulating tape. I suspect there's lots leaking along those wires. i'm now going to trace those wires from the alternator to their various destinations. Do you know if the alternator wires can be purchased as a single entity. I'm reluctant, financially and time wise, to replace the whole loom, though I know I'll probably have to at some point, I just want to get her running and recharging the battery so we can get out with the lid off..

Thanks.
spins

Thanks to all of you fro your guidance, after expending lots of knuckles, insulating tape and swearing and shouting, I'm now getting 13.9v at the posts.and it charges. Hurrah! Took her out for a spin and while there are lots of issues, see the picture on New on here forum and you'll see what I mean.

The adventure continues...

Have a good week.

spins

Hi you can make up the cables I use some 3 x 2mm originally which is fine but added a new 8 mm cable across in addition with ring terminals to the new alternators stud when i upgraded the alternator. The issue is that as the alternator is sensing the machine, any volts drop through bad connections or too small sized cables results in less power down the cables as it backs off at 14.4 volts even though battery voltage may be only 13 so you don't get the performance. If you are unsure measure cable and expected current max output and put in the calculator here https://www.12voltplanet.co.uk/cable-sizing-selection.html I would look for no more than 0.3 volts drop at full load
You can buy new lucas plastic alternator plugs or solder splice the ends of the old cables out the lug to new cable and heat shrink to insulate and make a water tight joint, there are normally two connectors for the supply over to the battery or starter solenoid point from the alternator and a small lucas terminal supplying the filed voltage from the ignition control via the charge lamp. This does nothing once alternator starts to make its own voltage As i mentioned, i run the cables inside Copex plastic armour (screwfix) but you could also use thin rubber hose to protect mechanically under the block