Modified temperature gauge

[nero279]

Some may remember a few weeks ago a couple of links came up about a modification to the factory temperature gauge.

(http://www.toyotasurf.asn.au/forum/v...ic.php?t=14717 & http://forum.ih8mud.com/showthread.php?t=64252)

I decided to give it a go, but had trouble finding resistors of the values mentioned. I ended up with 47ohm and 100 ohm 3 watt wire wound resistors encased in plastic and concrete insulators from maplins.

The mods been done a week now, and first impressions are that the guage is definately moving around a lot more, i'm taking this as meaning that it is giving a truer reflection of the actual engine/coolant temparature, as it seems to be doing what i would expect.

**It's worth noting that I have been running without a thermostat so i guess this could affect the gauge readings and they may calm down a bit once i re-fit a thermostat**

First time out it concerned me that the gauge seemed to take a long time to move at all, this could well be due to having no thermostat fitted.

I'm not 100% happy with the 'normal' position the gauge seems to assume when idling, or driving at low revs, it seems to sit on the far left of the gauge only 1 or 2mm right of the first mark.

Also when driving at high revs/ high speed the gauge quickly moves to the right hand side, which i guess it should, but i fear a sustained high speed ie)motorway driving might well cause the gauge to sit permanently in the red, i haven't been on the motorway since the gauge has been done but will see what happens on sunday.

After a run then a brief switch off (say 5-10 minutes), when you turn the ignition back on the gauge goes up into the red, the electric fan also kicks in. Guess this is due to heatsoak, and i'll be happy if the gauge goes into the red when or just after the electric fan kicks in although i would like it to go into the red at a slightly higher temparature than the fan kicks in.

I haven't bench tested it and don't plan on doing so.

[plumb bob]

Hi Ian, the long warm up time will be due to having no 'stat fieed, as when in place it would be closed and only the engine block water would be heated ( as I 'm sure you already know) and at low revs/speed and idle, the engine is not producing enough heat to get the system hot.

I think the main thing is that it shows the higher temp range, although the "going into the red" seems a little strange to me, it may be that the resistors you used have made the gauge over sensitive in the hot zone.

It may well be worth bench testing it, or getting another guage from a breaker to test it on.

Anyway, good work and well done on the write up, any help with temp issues on the surfs is always welcome.

Rob.

[dieselboy]

cheers nero. i understand this dead zone. makes sense. ive noticed with new cars that their RPM has a dead zone at tickover. you can hear the engine not constant but the rpm stays dead on 800.. it makes sense.

im keen to know what its like with a stat in. i dont like the idea of a large temp fluctuation with the stat out.
also if the needle is constantly going from cool to warm then i would be having brown moments every 5 mins.lol

let us know how your getting on?

[nero279]

yeah i'm gonna leave the stat out til after the weekend and get an idea of what it's doing on the motorway at the weekend, all being well i'll get a stat back in next week and see how it goes.

So far after a bit of heavy foot driving it hasn't made the red yet, but it's getting close, but it does 'seem' to be settling just before the red even with persistant lead boots. I'd just like it to settle a few degrees back, then if it does get hotter than normal for any reason there's still a bit of room on the gauge to judge how much hotter it is.

[nero279]

On the way upto woodlands on sunday the guage was good, at 70 mph it sat about 2mm off the red, moved up a notch on slight hills to just touching the red, and dropped a notch when going downhill.

It's still a little high for me though, but the difference when travelling a touch slower surprised me. At 55mph ish on the way back the gauge sat literally just past half way but still moved about slightly so i'm happy it wasn't sitting in a new 'dead' spot. Now bearing in mind this was after a pretty heavy days offroading and with a rad and engine half caked in mud.

It makes me want to bench test the whole thing, but i can't take my car off the road to do it at the moment, so if anyone's breaking and wants to donate a temperature gauge and sender i'll be more than happy to play with it and work out what it shows in real terms with different value resistors.