12 replies to this topic

[minimo]

Evening all,

I've just tried wiring in my Smiths water temp gauge and my voltage gauge but with no joy!

Could anyone give me some pointers as my loom is in a bad way and needs a rewire.

My water gauge is wired to the sender through one terminal and to the voltage stabiliser through the other.

My voltage gauge is wired to the earth trough one terminal and wired to fuse terminal 2 through the other. This keeps melting the earth wire!!!!! I don't want to lose my mini to a fire

Like I said this is the mess left by the last owner and could be way off the mark.

[lrostoke]

Where are you taking the earth from ??

[minimo]

Just checked and it's earth on the rear of the speedo.

With all the dial lights.

Edited by minimo, 22 August 2012 - 07:56 PM.

[lrostoke]

I think I'd be testing off the car first..Just to rule out faulty guages

Just hook up to a battery first...

How you said they were wired should be fine, black wires as standard are earths or any part of the metal shell.

[dklawson]

Following along with Steve's advice, there is absolutely no reason for a voltage gauge to cause melted wires if you are using a "decent" size wire. In the U.S. that would be something around 16 AWG. In most metric countries I would look for a conductor with 1.5 square-millimeters of conductor.

Having said that, I have a question for you and I encourage you to post back regardless of the answer so others may benefit. Are you SURE this is a volt meter you are installing and not an ammeter? See the pictures below.

Ammeters are wired very differently to volt meters. If you wire an ammeter from a power source directly to earth you will indeed smoke the wiring. Of the two gauges below, which does your gauge look more like?

[minimo]

Yea its a amp meter. Last owner had stuck a volts label over glass??????

The 50- and 50+ was a giveaway.

Is there any benefit in having an amp meter?

[lrostoke]

Not really ..better with a proper voltmeter

[Doz1971]

An ammeter was really designed for use in a dynamo equipped car. IMHO a damn dangerous thing to have in a car, as all the current from your battery must pass though it, with associated big cabling and risk of rubbing through bulkheads etc...... ghastly. If you have an alternator, get a volt meter.... If I had a dynamo, I'd still get a voltmeter !

[Doz1971]

In answer to your water gauge issue... try grounding the temp sensor on the head, your gauge should then read full scale. Check this first. If it doesn't you may need to reverse the wiring on the rear of the gauge. Some gauges need an un-stabilised 12 volt supply straight from the fuse box, rather than from the voltage stabiliser.

[minimo]

Why the hell would anyone fit it unless the dash came from an older car once?

Cheers for the help all and thanks for stopping me from having a fire!

[dklawson]

Some people like ammeters and you will never convince them otherwise. I do not dispute that they have their uses but I am in agreement with Doz that they can be dangerous. The most common issue I see with them today is MOST old ammeters (Lucas and Smiths) were +/- 30 Amps, not the 50 shown in the picture link. While the early Lucas alternators could only deliver about 34 Amps, later alternators were bigger and more powerful. You really need to have the wiring and any ammeter in that wiring sized to handle the highest possible output from the alternator even though it is unlikely the maximum current flow would ever happen.

[tiger99]

You can get remote current sensors which just need the insulated wire threaded through them. but I don't know if anyone makes the necessary, fairly simple, electronics to make one work in a car. Maybe a bit of Googling will find one ready wired. They do completely remove the hazard of running the main unfused battery feed through the dashboard, and they avoid problems of voltage drop. On a Mini, you would fit the sensor over the bunch of brown wires coming from the main battery feed at the solenoid, so it measured total current, except for the starter motor. The indicating instrument would need to measure voltage, over a small range, or maybe a digidash would have the capability.

Maybe tomorrow I will be abe to find some info on the appropriate sensor. The catalogue is at work.

An ammeter is useful, if it can be implemented safely. We do get a lot of people here with charging problems, and if you know both volts and current you can often rule out items which might otherwise be suspect such as the alternator.

[dklawson]

Tiger, my acquaintance Steve Mass made a unique gauge for his A-H Sprite. His gauge does not inductively couple to the wiring like perhaps you are suggesting but it is still a neat idea. Sadly , Steve has sold his Frogeye so I don't hear as much from him as I once did.
http://www.nonlintec...sprite/ammeter/

There is another type of ammeter that is marginally safer for use in modern cars without being inductively coupled to the wiring... the old shunt-style ammeters. With them, a large heavy resistive element is placed in series with the power from the alternator to the battery. An accurate voltage gauge is connected across the shunt and measures the voltage drop due to the current flow. They can get hot and are therefore somewhat difficult to mount safely where they can both vent heat but not be accidentally touched. Regardless, when that type of ammeter is used, only low voltage wires need penetrate the firewall as a calibrated volt meter is used for the readout/display.