Voltage regulator(?)

[yandy]

Hi all,

I finally have +2, and it comes complete with all the proper niggly problems. These I'm slowly working through - slowly because I'm trying not to bodge it, as I may otherwise be wont. I enjoy trawling the archives of this forum, but occasionally come up with something that just needs an explicit answer - here's one of those things:

Some essential background, the problem, a theory, a further problem, and a grumble with a request for recommendations:

Essential background: it's a 68 +2 (non S) with an alternator conversion (-ve earth (edited from +ve earth idiotically put in first posting)) and solid state voltage regulator.

The problem: fuel gauge and engine temp gauge have stopped working. They worked for about 50 miles.

The theory: dead voltage regulator, as I think these two both run through that, and it would be a big coincidence for them both to go at the same time otherwise. Can the voltage regulator be tested to verify this? I'd really appreciate some back-up or shouting-down on this theory.

A further problem then: the above being the case, it's disturbing because the voltage regulator was very new - put in just before I got the car - could this signify a more fundamental problem expressing itself in fritzed voltage regulators?

A grumble with a request for recommendations: I put a similar item in a Triumph previously and it solved all the wacky gauge problems in that car well too - and then died after a few months. In theory I like them but are they all just as cheap and nasty as they look, or is there a better quality version about that anyone can recommend?

Cheery,

Andy

[ncm]

It would be surprising to find a car with an alternator still running positive earth. I am aware that it used to be possible with a Lucas AC alternator that used a seperate regulator box but would expect that you have an ACR machine with a built in regulator. Could it be that you have wired in the solid state gauge regulator back to front as you believe the car to be positive earth when in reality it is negative earth?

Brian.

[yandy]

Duh! It's me that's wired the wrong way.

The car is of course negative earth, and it's wired in the right way for that. Sorry! the question is still valid subject to that correction.

[neilsjuke]

The voltage stabiliser must be earthed to work
Neil

[stugilmour]

Assume you mean the voltage stabilizer, a small component mounted to dash that knocks down gauge supply to 10 volts stabilized for the fuel and water temp gauges.

Agree it sounds fishy if both these gauges have gone south, but other instruments working.

A solid state replacement is available from Moss Motors in the US. Here is a link to description. The same one is used for several British cars in their parts listings. Document also has trouble shooting instructions.

http://www.mossmotors.com/graphics/prod ... 31-555.pdf

I bought one, but have not tested yet as dash still out of car. It fits Lotus and wires simply. Need to specify +ve or -ve ground as required (not interchangeable).

Agree check ground to the one you have. ground to mounting lug on some of them; believe some have ground connection.

[RichardS]

Andy

If you need a new voltage stabiliser you can buy one on Ebay http://cgi.ebay.co.uk/SOLID-STATE-VOLTA ... =72%3A1689

It is an easy replacement for the original type.

Richard

[c.beijersbergen]

If you want to make a solidstate stabilizer yourself take a look at:

http://www.nelli.org/techtips/vreg.shtml

Cor Beijersbergen

[gerrym]

Yandy, assuming we are talking about the voltage stabiliser to the gauges (Nothing to do with the Alternator voltage regulator).

You have a Plus 2 (Not S and Not S130). It has 4 auxilliary 52mm gauges, ie fuel level, oil pressure, water temperature, amps.

Is the oil pressure gauge electrical or mechanical (if its electrical it will have a needle movement arc about 120 degrees, if its mechanical it will be about 270 degrees). Have you double checked that the water temperature gauge is electrical (same check as per oil pressure gauge but also check the sender under the thermostat).

OK, if its just the fuel level gauges and the water temperature gauges that are electrical, and powered through the voltage stabiliser, check out the voltage readings of the power supply to the gauges with the engine running (without the stabilser will be around 14.5V) and with the engine shut-down (should be around 13.5V declining rapidly with headlights on for 5 minutes to around 12.5 volts). If the gauges see a steady voltage regardless of car working voltage of around the 10 Volts, the voltage stabiliser is working OK. If they are seeing the full voltage variation, there lies your problem.

Note, before you get behind the dashboard and start probing away with the multimeter, you could perform pretty much the same test in a qualitative way by comparing the fuel gauge readings with the car stationary, engine on and engine off.

Note 2, Yandy just re-read your post and noticed your gauges appear dead. Provide a separate power supply (eg DC 9Volts from a battery pack) to the fuel gauge and observe readings) This will give you a pretty quick diagnosis of the problem.

Regards
Gerry

[yandy]

Thanks all for the very comprehensive replies. Especially Gerry.

Yes it is the voltage stabiliser that's suspect, and it's all connected up and grounded correctly (from a visual inspection anyway). The gauges (both electrical - thanks for the identification tip) are not reacting at all, hence suspecting failure of the stabiliser, but it occurs to me that that doesn't rule out the feed to it simply being disconnected somewhere. Multimeter out and some more investigation into that can be carried out.

Would by-passing the stabiliser temporarily (i.e. putting >10v through the gauges) for the purpose of testing be a Very Bad Thing?

If nothing's obvious, I'll stick another stabiliser in and see if that solves it. Hopefully a new one won't fail so quickly.

Cheers,

Andy

[gerrym]

Yandy, is your oil pressure gauge mechanical or electrical? If its electrical and working, then this eliminates the voltage stabiliser as a problem. If it's mechanical, then it can't be used to infer what the problem is.

For what it's worth, I would NOT directly correct system voltage to the fuel gauge. With 14.5V you will be putting a lot more current (= energy) into the sender resistance. If its above the level of the fuel, then there will be little energy dissipation.

A dry cell battery pack of nominal 10.v + volts should do the trick (=7 cells in series). Do you have a battery for your drill/screwdriver. Check the voltage, it may provide an alternative

Regards

[yandy]

Hi Gerry,

Hmm, the oil pressure gauge is electrical and it is working. That didn't disturb me though (until now!) because the baroque wiring diagram in the workshop manual suggests (to my eye) that only the fuel and temp gauges ran through the stabiliser, with the oil pressure gauge independent of it.

As only fuel and temp were the ones not working, the stabiliser was suspected.

I assume you're suggesting the oil pressure gauge feed also runs through the stabiliser and if working therefore throws the failed stabiliser theory out the window. Or perhaps it's something more cunning than that.

I may then be looking for a disconnected wire somewhere in the fuel/temp part of the stabilised circuit, or the possibility of two independent but coincidental faults.

Thanks for your continued assistance,

Andy

[gerrym]

Yandy, sorry I have confused the issue re the oil pressure gauge. This is NOT driven from the voltage stabilised source. Check this forum technical tips, electrical, classic Smiths gauges.

Regards

[yandy]

Phew! I was hoping that was the case. And that diagram is much more useful than the workshop manual one.

OK, so all in all, it seems I'm looking in the right place, and now have some more useful advice on testing. Will get to it. Thanks.

[john.p.clegg]

Yandy

I have tested your Voltage regulator/stabiliser and it's goosed (technical term) , (looked quite new - without mentioning too many names where/when did you get it?), one of mine is on its way,let me know how you get on...

John

[yandy]

Hi John,

Thanks for the confirmation. It's good news in a way, in that it identifies the problem.

As the stabiliser was new - it has probably only survived about 60 miles of service - there are two possible suggestions: 1) it was rubbish to start off with; 2) there's an underlying problem leading to stabiliser goosing - after all, it was in there to replace whatever broke before. I guess your high-quality item will allow me to test that.

I was slightly surprised to find two wires attached to the input (red and red/green). Does anyone know if this is normal - it doesn't seem to be reflected in the original standard wiring diagram, although the car has been rewired. Could this be contributing to the goosing dynamic?

I'm not sure where it came from. The car is new to me, but the PO is on this forum so may be able to share that with everyone.

Thanks again,

Andy