1997 900 NA 2.3L. Does anyone have the information on what the resistance of these should be? This is the coolant temperature sensor up in the head between cylinders 3 & 4 just below the intake manifold, not the one that runs the gauge down by the thermostat housing. I got a new one because I suspected a problem and I am getting significantly different readings from the one still installed in the car. The car has not been run in days and the new sensor has been sitting in the car, so they should be reading close to the same reading as they are both at the same ambient temperature. Thanks.
jotzgr
The temp sensor in the block will give you a different resistance reading as the metal is in contact with the block (as it should ) and the new one is out in the open and either your holding it and changing the resistance, recently found this when changing an aftermarket unit for an OEM, and was effecting cold startup and idle. Not quite the same for a T5 unit as this was a T7 but the #'s may make more sense to you now.
Is your SAAB 1997 working properly?
Any temperature sensor is a NTC-resistor.(Negative Temperature Coefficient). Typically reading 100 ohm at 100 degrees C (212 F), and 5 000 ohm at 0 degrees C (32 F).
Any temperature sensor is a NTC-resistor.(Negative Temperature Coefficient). Typically reading 100 ohm at 100 degrees C (212 F), and 5 000 ohm at 0 degrees C (32 F).
Motronic? I think it's this one: Coolant temperature sensor – NG900 1997 | SAAB Workshop Information System
(edited, the chart has a typo and the higher temps are OHMs not Kohms)
(edited, the chart has a typo and the higher temps are OHMs not Kohms)
That's really interesting... I wonder why Bosch used a PTC with Motronic. Newer Bosch fuel injection and older Bosch fuel injection all uses NTC.
Bob - NTC sensors change resistance logarithmically with temperature... Lower resistance at higher temperature. That curve is described by the beta value aka the Steinhart-Hart equation.
Bob - NTC sensors change resistance logarithmically with temperature... Lower resistance at higher temperature. That curve is described by the beta value aka the Steinhart-Hart equation.
Now I wanna look in real WIS and see if it's different. It would definitely be weird for Bosch to use PTC on one version of Motronic in the mid '90s.... But for a while every Bosch EFI scheme used a unique sensor (all NTC but different beta) so it's not like they strive for consistency. 
My 1997 900 with B234i engine had two temp senders. One went to the gauge, the other went to the ECU.
The temp sender that goes to the gauge (via ICE) also is what controls the fan.
In my case, the ICE/gauge temp sensor's leads frayed at the sensor and gauge would drop to zero. For whatever reason, the fan did not run and of course the engine would heat up.
I would say that if the temp gauge is sitting properly at 9 o'clock then the temp sensor is working fine and the fan may or may not need to run. If there's a problem with the fan not running, it's not because of the ICE temp sensor.
This can be double-checked with an ODB II reader. The engine temp reported there will be from the alternate temp sensor used by the ECU.
The ECU temp sensor is called out as an NTC. WIS appears silent on the nature of the temp sensor used by ICE. Other than there are two versions, a metric and a non-metric that changed some time in MY'97. Shop had fun replacing the sensor, inevitably I guess the first sensor they got did not fit my car.
This was all a long time ago and I may have gotten fuzzy on some details.
The temp sender that goes to the gauge (via ICE) also is what controls the fan.
In my case, the ICE/gauge temp sensor's leads frayed at the sensor and gauge would drop to zero. For whatever reason, the fan did not run and of course the engine would heat up.
I would say that if the temp gauge is sitting properly at 9 o'clock then the temp sensor is working fine and the fan may or may not need to run. If there's a problem with the fan not running, it's not because of the ICE temp sensor.
This can be double-checked with an ODB II reader. The engine temp reported there will be from the alternate temp sensor used by the ECU.
The ECU temp sensor is called out as an NTC. WIS appears silent on the nature of the temp sensor used by ICE. Other than there are two versions, a metric and a non-metric that changed some time in MY'97. Shop had fun replacing the sensor, inevitably I guess the first sensor they got did not fit my car.
This was all a long time ago and I may have gotten fuzzy on some details.
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