converting + earth to - earth?

[3759allen]

hi all. new to the forum as i've not long started working on a friends +2 for her, i've come across a few issues and am slowly working my way through them.

my first task is to complete the + to - earth, it looks like the previous owner has started in order to fit electric ignition but looks like progress has stopped there.

i'm trying to find out what else is required.

i believe the tach needs converting, spiyda seem to offer both the parts and a conversion service. has anyone done the conversion themselves, if so how easy is it? has anyone use their fitting service and is it worth just getting them to do it?

i've read the ammeter also needs converting/ swapping, i'm hoping this is the case as this one is reading -. does anyone know where to get the parts and how easy it is to replace?

also read about the clock needs replacing, although this isn't immediately important but has anyone done this conversion?

finally is there anything else that needs converting/ replacing?

thanks

[stugilmour]

i've read the ammeter also needs converting/ swapping, i'm hoping this is the case as this one is reading -. does anyone know where to get the parts and how easy it is to replace?

Welcome to the forum. Sounds like a great project. What year and model is the car? Actually, top tip is to put the year, model, and drive position in your signature so it shows in all your posts; the Plus 2 had a lot of variants, particularly in things electrical.

I would recommend ditching the ammeter altogether in conjunction with your most excellent plan to upgrade to an alternator. The Plus 2 Workshop Manual even specifically covers the upgrades of older models to the Lucas alternator, and they replace the ammeter with a “Battery Condition Gauge” or voltmeter. The illustrated gauge looks terrible; a modern Smiths Voltmeter is a way better match to my eye. Trying to recall, I think mine needed a bit of fiddling with the gauge light and bracket, but would be easy with the dash out.

I would recommend replacing the main charging wire that goes thru the ammeter now while removing/modifying the stock voltage regulator. Note the Elan didn’t have a stock ammeter, and the kit instructions might need a bit of filling in with the Plus 2. Anyway, that can all be sorted when you get to details.

I would get the tach done professionally. Not worth the aggravation. Spiyda should be fine.

I assume the radio (if present) would need attention?

All the best with the project. And remember, it didn’t happen without pictures…

[Andy8421]

The comment above about replacing the main charging lead with a straight connection from the alternator to the battery terminal on the starter relay/solenoid is very good advice.

The original connections to the ammeter are unswitched, unfused with decent current carrying capacity. There is many an Elan driving around on that roadway in the sky because of an under dash electrical fire. While it is difficult to pin these events down to a specific cable, the ammeter connections are definitely a hazard.

[ericbushby]

Hi
You can change the tachometer over yourself if you are comfortable with this sort of work.
Just two connections to change over inside and replace two ageing capacitors on the circuit board while you are there.
I have done an earlier type with no difficulty and some satisfaction.
List the year and tacho type number for further help.
Eric in Burnley
1967 S3SE DHC

[3759allen]

Sorry for the delayed response, I've been so busy with work the project has been on the back burner.

Thanks for all the advice. Given my lack of time at the moment I think it's probably best to send the rev counter to get sorted.

Thanks for the good shout on the wiring to the starter solenoid and voltmeter.

I'm assuming the temp gauge / sensor should work regardless of polarity?

[Andy8421]

Sorry for the delayed response, I've been so busy with work the project has been on the back burner.

Thanks for all the advice. Given my lack of time at the moment I think it's probably best to send the rev counter to get sorted.

Thanks for the good shout on the wiring to the starter solenoid and voltmeter.

I'm assuming the temp gauge / sensor should work regardless of polarity?

Not sure if your car has an electric temp gauge or capillary. If capillary, it doesn't care.
If electric, Smiths instruments work off 10V and have a 'stabiliser' attached to the back of either the rev counter or speedo that drops the voltage from battery voltage to 10V. The original stabilisers are electromechanical, and don't care about polarity, modern replacements are electronic and do. Most suppliers of the replacement stabilisers sell positive and negative earth versions.

[stugilmour]

Just to confirm, the Plus 2 temperature gauge is indeed electric and the stabilizer is generally located as described above. There is a black ground wire to the outer case and two terminals for the input 12v and output 10v. Even if it works correctly after the polarity change, I would recommend replacing the original with the solid state type while you are in there. In this case the unit is changed but the connections stay the same.

From looking around the internet it appears that other than the solid state stabilizer issue mentioned above, the fuel and temperature gauges should be OK with the polarity change (these are the only two gauges use the 10v stabilizer supply). Good question, and not really 100% sure from my own experience, but easy to fix after testing.

To clarify on the tach, I assumed (in addition to changing polarity) Spiyda will be replacing the internals to the internal sensing coil style that work better with electronic ignition. In any case, this is a service they offer and seems well recommended. Good choice to get it done and to get their upgrade.

Just looking at various internet sites, other things to check would include the coil and any electronic ignition components, the heater fan direction and the radiator fan direction. I think you already mentioned the clock.

With the ammeter gone (it would read backwards if left in place), the new voltmeter wiring is very straightforward; I wired mine to White - Hot in Run & Start, unfused as I didn’t want any potential voltage drop from a dodgy fuse connection or whatever.

What year and model is the project? Totally understand having to have the project on hold for a bit; hopefully we can help you group some of the jobs together or at least not have to take the dash out multiple times.