coolant sensor mod

[MetroMPG]

jangeo: took your advice and got a reading of 21.1k ohms at the next (200k) level on the DMM over the full resistor (the 2 outside contacts, not the wiper).

i realize i just need to substitute the pot for the additional WTS and resisitor in the wiring diagram, a few posts higher up this page. so the pot will be in parallel to the existing WTS.

what i'm not sure about is the 3-wire setup on the pot. i know what to do with the input wire, but not certain what to do with the wiper wire and the last (outside) wire.

do i join the two together as shown in the "variable resistor" option on this diagram:

<img src="http://sound.westhost.com/pots-f6.gif">

[JanGeo]

Yeah the one with 1+2 connected together is the preferred method because it maintains some resistance in the in-out connection should the wiper not make perfect contact with the resistive material. Only thing to think about is if you want the resistance increase in a clockwise or counter clockwise direction so wire accordingly.

[DRW]

Hello, yes I know I'm digging up an old post, but I wanted to share my experiences with wiring a 10k pot to my ECT sensor.

I originally did this to my '92 Eagle Talon AWD because I had a cooler thermostat installed and I wanted to fool the ecu into thinking the engine was warmed up so it would stop enriching the A/F mixture all the time. I have a logger that reads ECT(engine coolant temp, aka WTS) and IAT(intake air temp), among other things. I used IAT as a reference since both would be the same when the car has been sitting overnight. I adjusted the 10k pot until the ECT read about 15 degrees higher than IAT. Then I tried to start the car. It took a couple tries to start it. Observation #1, ECT has a significant effect on startup enrichment. So I readjusted the pot to read 10 degrees over IAT.

Then I drove the car until it was warm and ECT stabilized, indicating the thermostat was open and regulating ECT normally. Normal temp was about 185 degrees, and with the 10k pot the ECT read 187! Observation #2, this is not a linear sensor curve. Eventually I had to reduce the ammount of adjustment made by the pot to the point where it wasn't really worth it. The car was still hard to start when cold, and there wasn't enough change when warmed up.

Your car appears to be quite different. Heres' your chart;
WTS resistance/temp:

F --- C -- OHMS

210 - 99 - 190
160 - 71 - 400
100 - 38 - 1250
070 - 21 - 2350
040 - 04 - 4780
020 - 07 - 8100
000 - 18 - 14650
Lets say you subtract 200 ohms with the pot. At 160 degrees actual temp your ecu would think it's about 205 degrees, a difference of 45 degrees. At 40 degrees actual, the ecu would read 43 degrees. It looks like you could adjust the resistance by 100 OHMs and see a difference. So in your case you could subtract just a little resistance without affecting startup too much, then as the car warmed up the difference would get bigger. There shouldn't be as many compromises to driveability at higher temps. Since the ammount of adjustment is small I'd recomend a pot with a smaller rating to keep it from being too sensitive to small adjustments. I'd say give it a try and see how it goes. It didn't work so well on my car, but every car is different.

[onegammyleg]

Hi DRW -&#168;Hello, yes I know I'm digging up an old post&#168;

Now thats an old post !

[DRW]

Har har har a-hawhaw