[Diy_efi] two part ect sensor Q

Torbjörn Forsman torbjorn.forsman
Tue Mar 14 17:15:44 UTC 2006

1) At least on european GM cars, the sensor for the coolant temp gauge 
is a NTC thermistor of about 500-1000 ohms at +25 ?C. Usually, the gauge 
is a bimetal type which is supplied by stabilized +10 V.
It is simple to figure out the characteristic of the gauge by connecting 
various fixed resistors instead of the sensor and watch the reading. The 
sensor is simply connected in series with the heating resistor for the 
bimetal element. If you can remove the gauge block and measure the 
resistance of the heating resistor, then the sensor should probably have 
about the same resistance when the gauge reads mid-range.

2) If you need an ECT sensor with M12 x 1,5 thread for a GM injection 
system, then you can use either a Bosch 0 280 130 026 (very common on 
cars from the 80's with Bosch injection systems) or a GM 25036898 or 
25037062. The GM sensors are normally marked with just the four last 
digits. Although the caracteristic is not exactly the same for the Bosch 
sensor, the difference is nothing to bother about in practice.

Best regards

Torbj?rn Forsman

Michael Kaczmar wrote:
> 1) On a mid-90's GMC full size pickup, what electrical range does the
> coolant temp guage read in? Truck used to have a TBI 4.3L, I now have
> an LR4 (4.8L Gen-III) in the my 93 GMC Sierra, and I'd like to get the
> temp guage working.  The service manual has not been all that
> informative on detailing how the temp gauge works. I no longer have the
> original engine, so it's hard for me to figure this out. Anybody know?
> I believe it's a 5V dc circuit, but am not sure. 
> 2) I plan to retain the stock on in the stock location (drivers side
> cylinder head), but run a seperate one on the passenger head. The port
> in the head for the ECT sensor is a 12 x 1.5mm thread, so either I need
> this thread, or a 1/8" NPT fitting, as there are adapter bushings
> available that have a 1/8" NPT Female with a 12 x 1.5 mm male. 
> Any help  is appreciated. 
> Michael Kaczmar
> Creator 77/94/95/96 Caprice a.k.a. Frankenstein LT1/MN6
> 2004 Impulse Blue GTO, LS1/M12
> 53 F-100 5.0/T5, Mustang II, T-bird IRS.....
> see http://www.geocities.com/abbynrml94 for project pics!!
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