Purpose of the two temperature sensors in the ng900. - The Saab Link Forums

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Performance Modifications for the NG900 / Old 9-3 This forum contains PERFORMANCE related Q&A's for the NG900 and 9-3. This may also include suspension.

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Old 04-23-2014, 03:30 PM   #1
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Purpose of the two temperature sensors in the ng900.

The t5.5 ng900 has two temperature sensors in the wiring harness. One goes in the thermostat housing and the other goes to the middle of the head, actually bolted into the intake manifold.

Can someone confirm what purpose each of these two temperature sensors serves? I'm guessing that the one in the head is used by t5 for some fuel multiplier, and the one in the thermostat housing is only used for the gauge cluster. Another theory is that one of these is a potentiometer and the other is a simple thermoswitch to turn on the idiot light.
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Old 04-23-2014, 03:58 PM   #2
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Correct. One for the gauge, one for input to the ECU tuning purposes.
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Old 04-23-2014, 04:07 PM   #3
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Cool, so the one in the thermostat housing is the one for the gauge?
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Old 07-24-2014, 04:26 AM   #4
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I made the mistake of letting someone else replace my stretched timing chain because I really didn't have the time. They put in the wrong thermostat and as long as the car was cold it ran fine, but as soon as she warmed up.. it surged like crazy and wasn't drivable.

I learned that if the thermostat opens too quickly.. or the temp fluctuates too much the water temp sensor picks up on it, and apparently tells the ECU because I couldn't get any boost. It kept popping CELs and she stalled and surged like crazy after warming up. I researched the CEL, then experimented by disconnecting the temp sensor and she ran great but rich. Then like a mystical spirit of SAAB whispered in my ear.. "hey dummy, what device physically changes with temperature"

Replaced the temp sensor and reconnected, and no go because it ran like crap after she warmed up again.. I kept hearing, "hey dummy what device changes with temperature".. so I popped the thermostat housing and discovered some strange looking thermostat was the culprit. I was livid.., (never thought I'd use that word in a sentence.. lol)..

So yes.. that temp sensor does something too...
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Old 07-24-2014, 08:54 AM   #5
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Quote:
Originally Posted by jerrit View Post
Cool, so the one in the thermostat housing is the one for the gauge?

Correct.
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Old 07-24-2014, 12:40 PM   #6
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Quote:
Originally Posted by jerrit View Post
The t5.5 ng900 has two temperature sensors in the wiring harness. One goes in the thermostat housing and the other goes to the middle of the head, actually bolted into the intake manifold.

Can someone confirm what purpose each of these two temperature sensors serves? I'm guessing that the one in the head is used by t5 for some fuel multiplier, and the one in the thermostat housing is only used for the gauge cluster. Another theory is that one of these is a potentiometer and the other is a simple thermoswitch to turn on the idiot light.
I may have misunderstood part of the original question.. to read as is "the one in the thermostat housing is only used for the gauge cluster?.."

Simply stated., it is not only used for the gauge cluster.. please forgive my insolence almighty former Saab Tech / Competition Preper
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Old 07-24-2014, 01:09 PM   #7
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Cool, so the one in the thermostat housing is the one for the gauge?
That one provides the signal for the cooling fan also
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Old 07-25-2014, 09:05 AM   #8
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Actually the ecu uses both for tuning purposes. There are copious temp-dependent maps for all sorts of parameters...if you have an auto its even worse.
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