voltmeter in the TOP red above 15

[Russ35]

On Sunday and today I noticed that the voltmeter was higher than normal sitting above 15 and sometimes in the TOP red area. If you turn lights, heater, indicators you get the normal jumping needle but higher readings than normal.

I've put the multi meter on and got the following on the battery and got the following

	Voltmeter	Multi Meter
Engine Off	0	12.6
Key turned	between 14 and 15	12.6
Started	between 13 and 14	12.25
Revved to start charging	>15/Red	14.4
lights, heater, indicators	jumps between 13 and red	between 13.9 and 14.4

Any suggestions or other tests to try?

[tvrgit]

I would say your multimeter readings look right, so I would suspect the voltmeter or its wiring.

If you can get your multimeter to check the actual voltage at the back of the meter, that might give a clue.

remember too, that the voltmeter measures the difference between "live" and "earth" - so if the gauge's earth is crap...

[Russ35]

Should be able to reach the voltmeter via the glove box (more accurately my brother will with his smaller hands), so will try that tomorrow.

[Le TVR]

Symtoms are:

• battery gone high resistance (replace)
• battery connections/earth points gone high resistance (clean)
• alternator controller suspect

Probably in that order.

[Russ35]

Just had the gauge out from the dash and took readings from the back, and all seems ok going into the gauge, so looks like I need to get a replacement gauge.

I did notice when taking the gauge out that its starting position is high up in the bottom red, so have just found an old photo I'd taken that shows its default position is below the bottom red area.

[Barkychoc]

I'd take it to bits first - its already knackered so what have you got to lose?
Could just be something come adrift inside.

[mep12345]

There have been a few of these (new ones) on ebay recently and they have been going for a song, worth a search - the seller was in blackpool ( an ex employee maybe)

[Russ35]

mep12345 said:

There have been a few of these (new ones) on ebay recently and they have been going for a song, worth a search - the seller was in blackpool ( an ex employee maybe)

I know who that will be. I got a new rev-counter (as a spare) from him last year. You are correct he is ex-TVR, assuming it is the same person.



I've got it working again. Took it to bits and repositioned the pointer. Not sure how it was pointing wrong as it was a tight fit. Just got to get a bit of matt black paint to touch up the scratch I made removing the front bezel.

[johnnywgk]

Russ when you put it back together, put in a sachet of silica, he stuff you get
when you buy electrical goods, to absorb moisture.

It might stop it misting up, and do let us all know if it works, cheers.

[Russ35]

Good idea on the Silica. Just found a pack that came with a network card I bought recently, so I'll put it in.

I've just gone back to look at the photo I mention above and guess what, oil pressure, fuel and temp are all misted up, but the voltage gauge is clear I'll still put the silica in. I might have some more laying around if I look, so I might take one of the other gauges out and put it in that one also.

[johnnywgk]

As i'm in double glazing, that gave me the idea, they use silica beads in the spacer bar between the 2 sheets of glass, so any failure in the sealed unit, the silica absorbs the moisture, to stop condensation inbetween the 2 sheets of glass.

It might be a good idea to put some silicon on joints and holes where wires/cables
go through.

The other way around the misting, would be drilling holes in the casing to let air flow through (like a windscreen demister)

Let us know how you get on.

Cheers.

Sorry to go on, been drinking all day.

[Russ35]

Well my repair seems to have lasted till the return trip from Chatsworth. No reading all the way back. Checked all the connectors and it's as dead as a dodo.

So called in to see the guy I mentioned above and managed to pick up the last voltmeter he had for the grand total of £5. Put it in and the first thing I've noticed is that there is no jumping up and down when the indicators are used, just a very small movement.

Now to have another go at my Speedo.

Edited to add that I tried the Silca idea but the bags I had were all a bit to big to fit in.

Edited by Russ35 on Monday 26th April 13:14

[CTE]

The better solution to prevent misting is to drill vent holes. We have similar problems in electrical enclosures in the plant hire industry...manufacturers use very nice IP67 enclosures, which do an excellent job of trapping airbourne moisture which leads to condensation inside the enclosure. Silica bags only last so long before they become saturated.