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Temp gauge  Rating:  Rating
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 Posted: 08-14-2005 01:12 pm
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Dave
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Is there by any chance a drop in replacement that has the actual temperatures listed on the gauge?

I watch that needle run over towards the red on our hot sultry east coast days and wonder to myself, how hot is it getting, really......?

and in everyones experience, how far to the right can that needle get before there's trouble? Can you trust the red line?

Thanks, yet again,

Dave
16985

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 Posted: 08-14-2005 06:22 pm
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Mark Rosenbaum
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I've attached a composite photo showing the stock JH gauge on the left and a couple of alternatives that might suit.  The case diameter for most Smiths small gauges, including those used in the JH, is specified as 51.4mm to 52.0mm.

You can install a gauge purchased from a wrecking yard, swap meet, or via eBay, and hope it works correctly.  As an alternative, since the internal parts of most Smiths gauges are interchangeable, you could find a (defective?) gauge with a suitable faceplate and swap the faceplate into your original gauge. 

That said, the presence of numbers on a faceplate does not make a gauge more accurate.  For any particular temperature, the needle's position will depend on the gauge's present adjustment, the behavior of the temp sensor, the output of the voltage stabilizer that powers the gauge, and even the air temperature near the gauge.  If these are all perfectly nominal, the mid-range indication should occur somewhere between 180^F and 195^F, while the red zone should start somewhere between 212^F and 240^F depending on the car manufacturer's desires.  For any particular gauge, the only way to know what an indication means is to use a calibrated thermometer and actually measure the coolant temperature. 

Finally, when overheating is a concern, what matters most is the temperature at which the coolant starts to boil.  This depends on the percentage of antifreeze in the coolant, the (absolute) current air pressure, and the (relative) pressure at which the radiator cap will start to open. You'd have to look up the figures for your specific set of conditions but as a rule of thumb can generally presume this to be 230^F or more.

 

Attachment: comparison.jpg (Downloaded 64 times)

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 Posted: 08-15-2005 05:49 pm
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StabnSteer
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The hole in the dash is exactly the same as the size you'll find most temperature gauges at the auto parts store - there aren't a giant number of sizes for the things, and the sizes tend to be really large in their differences, so an eyeball guess works just fine - it IS the one that looks like it would fit. :o) I replaced mine with one from Wal Mart of all places.

However, Mark's note about voltage is duly noted as my cheap gauge is VERY persnickety about voltage values and interestingly, it tends to slowly drift to the higher end of the scale as I drive...but if I turn the car off and immediately restart it, it seems to "reset" the gauge and it drops down to a respectable value again - but not before I tend to have that little panic feeling about the rising temperature. I'll likely try a more expensive gauge soon in hope that its electric bits are more trustworthy (I mean, why would it be more expensive after all...), just to keep my mind at ease.

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 Posted: 09-05-2005 12:01 pm
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Dave
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So in other words, as long as my gauge is working, there isn't much benefit from an "upgrade". Hmmmm. Maybe I'll break down and go the upgraded radiator route.....

Thanks again Mark!

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