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Does anyone know how to bypass the temp compensation on a 740?? 700

posted by Will740turbo on Sun Jun 29 20:21 CST 2008
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last visit: Wed Oct 22 16:09 CST 2014

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Ok, I'm having issues with my radiator (as usual :( ) and would love for my temp gauge to be a functional temp gauge, instead of compensated.
The car does get warm, and even if my radiator was fine, I would want to know when my temp is high, besides once it flips over to the red.

I haven't looked at the circuitry for the board, but I imagine there is an IC or something that can be bypassed relatively easily. If it's only an ohmeter, then there might be a discrete circuit to control the gauge, which would suck. Maybe an older gauge could be swapped in?

I saw a person mention that they had done it, and messaged them to see if they meant on a 240 or 740 and never got a response.

Thanks anyone,
Will
--
1990 740 Turbo, on its way to stock specs, maybe beyond

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740 temp guage circuit 700

posted by B.B. on Mon Jun 30 03:58 CST 2008
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last visit: Mon Oct 6 13:15 CST 2014

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I don't think there's much you can do with the circuit.
It is different than the 200 series.

I worked up a schematic if you want to try.
Whats your e-mail?

Bill

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740 temp guage circuit 700

posted by Will740turbo on Mon Jun 30 08:57 CST 2008
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last visit: Wed Oct 22 16:09 CST 2014

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I would really appreciate that! It's bigwilliex (at) hotmail. com

And also, it's not that it's malfunctioning, it's that it only reads warming up, *perfect*, or "bye-bye car".
I wonder if I could pull a 240's gauge and install it.
The car does heat up beyond *perfect* - this I know because one time I had been driving in the city and the car started losing power. I made a 2-minute stop and came back to the car to find it in the red (leaking heater hose) but until I restarted the car, it showed perfect.
Also a couple years ago, when the idle system was broken, I was sitting with the AC on (104F outside) and the car's idle started to drop down to about 400 - it was overheating, but the gauge said *perfect* as usual.
I've even gone to the point I bought an IR thermometer for $9 from Harbor Freight.

And what I've seen before is "there's no way to bypass the comp board" which only means that nobody has done it... yet ;)

Thank you for the replies!
-Will
--
1990 740 Turbo, on its way to stock specs, maybe beyond

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Does anyone know how to bypass the temp compensation on a 740?? 700

posted by SpazMan on Mon Jun 30 00:24 CST 2008
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last visit: Tue Aug 14 21:06 CST 2012

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Will,

I asked this same question a while ago, and was told there was no compensation board in 740s - any problems with the gauge should be caused by the water temperature sensor or its wiring, or maybe the dash gauge going out (I have to 'tap' mine occasionally).

I run a little warm most of the time, but at 12:30... not way in the red. I'm sure you would know if you were really overheating.

Ari

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