Temp. mod resistor

[PhilOutdoors]

I've just done this mod - using a 100ohm 2W resistor from Maplin (part number D100R here: http://www.maplin.co.uk/metal-film-2w-resistor-5729) and two insulated ring crimps. I left the diode alone and had similar results to you - ie. little effect. By shorting the diode with a few (careful) twists in the legs it seems to be working as described in the fact sheet -so far...

[mikeWalsall]

Thanks for that .. like I said .. it's such a simple job removing the clocks, I may short out the diode and see how the gauge reads then ..

[the1andonly]

mike
last night i made the same mod as at beginning of thread

http://www.maplin.co.uk/3-watt-wirewoun ... cification

a 100ohm 3-watt-wirewound-resistor

I used the same mounting points but soldered the ring crimps, had to file the leads for solder to wet.
I have left the diode alone
It works!
The zero with power on is approximately in same place as yours but on warm up moves to 12 o'clock
early days will see what happens when hot.I did see a small deflection around the 12 o'clock.
a quick check the cold zero position is the same
PS its a 97 4x4
spooky but my fuel gauge is also in the same position

[g8dhe]

Whilst changing the resistor will adjust the "normal" position of the gauge and slightly affect the slope around the "knee", the "knee" in the curve won't be removed until the Zener is removed and shorted or just shorted out by twisting the wires together.

[corrour]

Mine sits on C when cold
Rises to about 1oclock warm normal running
Moves higher when climbing then drops back on downhill or when fans in.
Did the mod 4 years ago
I DID BRIDGE THE ZENNER OUT
works perfectly

[the1andonly]

Geof
any idea why mike has a new zero but no 'knee'
what does the zenner do? what voltage zenner?

[mikeWalsall]

I did one other thing slightly different to the tutorial ... rather than crimping two 'eyes' onto the 'tails' of the resister ..

As the 'tails' where quite long, for simplicity and neatness .. I wound the wire around a small screw driver to form two 'eyes' .. and put the fixing screws through those ..

[g8dhe]

Perhaps you can confirm Mike;

Now when turning on the ignition the needle goes up to around 10 o'clock .. even with the engine 'hot' it barley moves ..

also Phil said;

I left the diode alone and had similar results to you - ie. little effect.

The change in the gauge reading is effectively "absorbed" by the Zener diode until it breaks down at the Zener voltage and starts to rise again thus allowing the gauge to move but only when the temperature is very high.

Details of the circuit here http://igmaynard.co.uk/bongo/forum/view ... 21#p556921 and more info from this site but it uses an old IE format http://www.tyrion.net/miata/tempgauge/90-93-MTGLP.mht

Its a 3.3V Zener.

[mikeWalsall]

Along with the other posters .. thanks for your input as well Geoff ..

I have read various tutorials including the 'quite involved' one ..

C:\Users\MY PC\AppData\Local\Temp\90-93-MTGLP.mht

But as others had already done the more simple mod. I went down that route ..

Just to recap .. I have not done anything with the Zenner diode .. just fitted a 100ohm 3 watt ballast resister to the relevant printed circuit board screws / connections by forming 'eyes' from the resisters wire 'tails' ..

Before fitting the resistor.. when cold my needle sat well below the 'square' start block on the gauge .. when warmed up .. raising to around 10.30 ..11 0'clock and staying there regardless of how long / far I had been driving ..

After fitting the resistor when cold the needle now sits at around 10.30 ... but stays there with very little upward movement, even when the engine is well up to temperature, (to the point of the rad. fans occasionally cutting in) ..

[the1andonly]

another thanks to geoff
just shorted the zenner
and after a quick slow test run
Mine sits bellow C when cold
Rises to about 1 oclock warm normal running 60-70 dual carr
and goes down a tad when tootling at 40
appears to work mike same 3w maplin resistor but soldered to terminals