"Normal" running temp ?

[Shiny_kit]

I've had a look through the archives but I'm still confused - can anybody clarify what is "normal" please ?
My temp guage has 85deg at 6 o/clock, with a marker to the right of it, unlabelled, then another marker at the start of the red zone, which is marked as ending at 120. My car seems to run at just past the unlabeled marker (90 ? 95 ?) if traffic is light and we keep a good speed - but if slowed by traffic will go to just short of the line where the red starts before the fan cuts in (now that it works, I am a bit happier about this, but it still seems a bit close). Several posters report cars running at 85 - which seems logical as with other cars I have owned having vertical needles as being "normal" so any deviation is seen at a glance. So, is my car normal, running a bit hot, or is my guage over-stating the temp ? Haven't checked the voltage regulator yet - must do that.

[Robbie693]

Hi,

I would suspect the gauge. Mine shows similar readings sometimes but not always, the fan cuts in anywhere from 88 - 95 deg. I don't remember but I think the otter switch is stamped 88deg, indicating what temp it cuts in at, which doesn't always correspond with what's on the gauge.

I measured the coolant temp with a multimeter and, although not totally accuate because of temp loss accross the rad, the gauge was reading high. I have a spare gauge which I need to fit and I'll be getting the original one recallibrated.

Robbie

[alaric]

Hi. The original voltage regulator is a bi-metallic strip that's heated by a current which is proportional to battery voltage. It opens and closes several times a second to give an average voltage of 10 Volts across the heater winding. If this is jammed shut or the heater wire broken you'll have ~13V instead of 10v across the guage and temperature sensor. The sensor is a device whose resistance drops with temperature, so having a high voltage from the reg will make the guage read high.

Here's a pdf describing the regulator in some more detail.

I bought an LM317 from ebay as a replacement but haven't used it yet as the Smiths reg seems to work fine. When I ran my engine recently it sat at 85 (needle vertical) under the control of the wax thermostat. I didn't leave it long enough to get the fan on but I think the needle should be vertical.

All the best.

Sean.