Instrument question

[stuartgb100]

Simple one ........

Is the combined oil pressure/water temp guage, as fitted to a '71 UK Sprint meant NOT to have an internal light ?

ie it's not illuminated when dash lights are turned on.

Regards,
Stuart.

[memnon]

Hi,

My 71 sprint's gauge is illuminated; my father's 71 sprint is also illuminated. Neither of us can guarantee authenticity. However, I have driven a car with an oil pressure gauge that wasn't illuminated and it cost me ?700 in an angine rebuild for a mini! So regardless of the authenticity I would never do that again

[stuartgb100]

I've loaned out my manual so can't check the wiring diagram at the moment.

It's something that's bugged me ever since getting the car.

Can't see that Lotus would let the 2 most important items of data be unavailable at night ( revs I can hear, speed I can feel).

Thanks
Stuart.

[alexblack13]

Hi All,
Far as I can tell it IS supposed to be lit. My Sprint diagram shows it. The old loom (original) had it fitted and my new loom also came with it fitted.

Why would it not be?

Alex B....

[bcmc33]

The gauge should be lit. But the standard 1.2W bulb is pretty dim. I fitted 5W bulbs to all my gauges. These bulbs maybe difficult to get but they're out there somewhere.
I Tried LED's but they are too one directional and dont give a good result.

The attached picture clearly show where the bulbs fit.

[Frank Howard]

the standard 1.2W bulb is pretty dim.

The standard bulbs are 2.2W and yes, it's not my old eyes. They are pretty dim however the modern matching Smiths ammeter I purchased came with a 4W bulb.

[collins_dan]

Frank, where did you get the ammeter, I was thinking about getting one? Actually, since I still have a generator, would I need an ammeter or a voltmeter? Thanks. Dan

[neilsjuke]

Ampmeter shows charge /discharge you can have charging faults showing voltage is ok but the current is low. It was cheaper to fit volmeters less heavy wiring .
Neil

[msd1107]

An ammeter and volt meter serve two different purposes.

The ammeter shows if the generator/alternator is charging the battery or if the electrical load is in excess of the current charging capability. This was more useful in the days of a generator, modern alternators have considerable charging capability even at idle.

A voltmeter shows the overall health of the battery. A well charged battery will show maybe 14v or a little more. As the battery is discharged, the voltage will be lower. Often, the voltmeter will have color coded segments on the display to make that determination somewhat easier. And if you are cranking the engine, the voltage reading can become quite low, and an improperly adjusted regulator can allow the charging voltage to get up to 15v or more.

All information for the geeks. Modern systems don't need gauges, just a discharge lamp is sufficient to alert you to a possible broken belt.

And it is true, a voltmeter is easier to wire. An ammeter needs wiring sized to the maximum amperage carried, and can be a bitch to route and wire.

David
1968 36/7988

[Frank Howard]

Dan,

There's a place 5 miles from me that sells and repairs them called API. Unfortunately, he's a jerk so I got mine at:

http://www.nisonger.com/smiths-classic-gauges.htm

You can order one with a black face. After it arrived, I took a bit of black paint and blacked out the lightning bolt.

I was told that if you have a generator, you're better off with a ammeter and if you have an alternator, you're better off with a volt meter.

I converted my car to an alternator however I chose an ammeter because:

1. My Europa (with factory alternator) came with an ammeter.
2. One of the extra gauges on a +2 is an ammeter.

Just seemed more period to me. Personal choice I guess.

[msd1107]

Be a little careful in ordering these new instruments.

Our Lotus Smiths instruments used subtly different typefaces and markings, and came in two different looks (at least). So compare the old gauge with a new unit. I'll bet that for most people, the differences are not enough about which to care.

It make take awhile, but used, NOS, or NIB units pop up on Ebay. The early speedo/tach and 60 psi dual gauge are the least common.

Even if you get a less than perfect used gauge, Nisonger can refurbish them.

David
1968 36/7988

[stugilmour]

The Plus 2 workshop manual has a pretty good write-up on the volt meter replacement for the strock ammeter. Is recommended in conjunction with a switch to an alternator. Basic points covered above; was a recommended upgrade.

If you have an alternator installed, I understand the ammeter range should be greater than the stock (for Plus 2) +30 to -30 amp. I believe the revised recommended range is +60 to -60 amp.

Got a voltmeter off eBay. Is sometimes called a battery condition gauge.

Lettering/style of the voltmeter is slightly different than the other instruments for sure, but it looks the same as the illustration in the Workshop manual. Another case of using what is about I guess!

[Frank Howard]

If you have an alternator installed, I understand the ammeter range should be greater than the stock (for Plus 2) +30 to -30 amp. I believe the revised recommended range is +60 to -60 amp.

The reason for this is because the modern alternators (used for conversion) produce anywhere from 35 to 55 amps or more. The one on my minivan produces 120 amps! I selected a 45 amp alternator for my Elan however I decided to go with the +30 to -30 ammeter because in most situations, there is a charge/discharge range of 10 or 20 amps. With a +30 to -30 ammeter, this is easier to read as opposed to a +60 to -60 ammeter. In the rare situation where the battery is completely dead and the alternator is charging it up, it will peg my +30 to -30 ammeter however the gauge will not be damaged.

[msd1107]

There is also a Smiths 50-50 ammeter (no model number on the face plate, a faint 5172 on the back). They are even less common than the 60-60 ammeters.

Imagine all the electrical items turned on simultaneously. Add all the wattages. Divide by 10. That gives you an idea as to the maximum capacity the alternator needs. Anything greater than that just complicates life. Wiring needs to be sized based on the maximum amperage, and you do not want to wire a car for a 120 amp alternator! High inrush charging current decreases the life of the battery. (cell phone, portables, EVs, and PHEVs use sophisticated logic to maximize the life and capacity of their batteries)

So in this regard, the original 22 amp generator was sufficient. Its main problem was it didn't generate 22 amps at idle, so the battery could be discharged on a cold, rainy night in stop and go traffic.

So as Frank says, the 30-30 ammeter will be sufficient, and give greater precision. On the other side of the coin, generally you are only interested in an indication of charge or discharge, not the actual value. Many ammeters just display a C or D.

And there are also threads on sourcing small, light alternators.

David
1968 36/7988

[stuartgb100]

Sorry to hijack back the thread !!!

but a couple more questions:

Any ideas for the following ..........

It's a given that I've not an original oil/water guage, so

where can I get one
has anyone a good close-up photo(s)
what other cars was it from.


Ok, back to the voltmeter/ammeter discusssion

(soory to interrupt)

Regards,
Stuart.