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Electrical fault traced to ammeter - what next?


BillyPee
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As some of you may know, my Westy died en route to the monthly meet last Thursday.

The battery was fine (hazards worked) but there was no live feed to the ignition barrel. RAC got me going with a temporary wire bypassing some of my (ahem) loom.

I found time yesterday to investigate and once I got behind the dash it turns out that the problem was really, really, simple to rectify. One of the wires going to the amp gauge had fallen off and connecting it back up completed the circuit providing power to the ignition barrel.

I'm still learning about car electrics but it doesn't seem right to me that a wire falling off a gauge should stop the vehicle from working (I'd have expected it to just mean that the gauge stops working). Or am I being too simplistic?

So I have spent some time searching the web learning more about how this gauge should be wired. Firstly, I have learnt a new word; the gauge is called an ammeter. It looks exactly like this product available from Holden:

070_022.jpg

Mine also is a 60 amp version (not the 30 amp) but without the SMITHS logo but is otherwise identical.

 

I then watched Holden's short video on Smiths classic 52mm voltmeter and ammeter gauges:

mqdefault.jpg

It seems that ammeters are inappropriate for vehicles with alternators (or at least serve no real purpose) so I am now questioning the benefit of fitting it at all. I haven't really paid any attention to reading the gauge in the past as all it seems to do is flick a little bit whenever I have my indicators on.

Any recommendations on how to proceed?

 

My options appear to be:

  1. Do nothing (well maybe just tidy up the wiring as its a bit short at the moment which is why it fell off).
  2. Leave the gauge in the dash but rewire so that a loose cable falling off doesn't kill the car at 3500 RPM on the dual carriageway! I was lucky this time, might not be so lucky next.
  3. Leave the gauge in the dash (as I don't want a 52mm hole in the dash) but rewire without the gauge being connected as it is neither use nor ornament
  4. Replace the gauge with a voltmeter as at least thats more interesting to read and is better than just a red battery light.
  5. Something else

Thanks in advance

 

P.S. This might be the start of a number of wiring relating questions as I can see me no longer being able to ignore all the mess of wires under the dash.

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I agree that you really don't need an Ammeter these days - after all, it tells you how many amps your drawing or charging but that's almost a "so what" these days of halogen bulbs, cooling fans and alternators etc etc.

 

And yes, in order to measure ALL the amps being consumed, your whole supply would (should) go through it (apart from the starter motor main supply of course) - so it requires thick cables (usually brown) and any failure will kill the electrics.

 

I'd replace it with a voltmeter (if only to fill the hole in the dash) but remember, the cables that went to the ammeter would be + in and + out but for a voltmeter you just need a relatively light cable +/- supply and earth

 

I'd join the two thick cables back together (either solder or "choc" block but not scotchlok !!) and then find a spare +/- for the voltmeter (you could take the + supply from the old + ammeter supply but as those cables are pretty thick already, adding another one just makes it more difficult to join up)

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Thanks both for the suggestions.

 

Short-term, i.e. next weekend, I am going to join the thick black cables going to the back of the ammeter together and bypass the gauge. Both cables have chocblocks in them already about 2 inches from the gauge (which suggests that they were extended as some point) so this will be really quick and easy to do).

 

I will order a Smiths Classic 52mm voltmeter gauge and install that over the winter lay-up when I tackle the rest of the wiring issues.

 

Thanks again,

Bill

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Just refit with unlock nuts - your thinking too much ! :-)

Guilty as charged. I do tend to overthink and overcomplicate as a result.

 

I have been reading-up a little deeper and found this wiring diagram which has helped me to understand just where the ammeter should be wired and why it is where it is. Might be of some use to people stumbling upon this post in the future.

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Even better would be run a new wire direct from the 12volt supply to the ignition switch, you don't want a thick cable joint flapping around under the dash.

If you are still having problems understanding how they are wired-----

Ammeters are wired in series to measure current being drawn.

Voltmeters are wired in parallel  to monitor the battery voltage.

 

Or maybe I've confused you even more :)

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  • 1 month later...

Minor update: As I've been working on the suspension and not driving the Westy, this job got put off until yesterday morning. I worked out why the cable fell off... its because the terminal on the back of the gauge is loose and when you attempt to push a female connector onto it the terminal just pushes into the housing and so you only end up with the very end pushed on (but it looks fully inserted because 75% of the terminal is inside the back of the gauge housing IYSWIM. So that made my mind up, and I have just bypassed the gauge.

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