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| Electrical Connection - Temp Gauge Sensor Plug (Page 2/3) |
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fierofool
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FEB 07, 04:41 PM
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| quote | Originally posted by Notorio:
This just keeps getting better. I'm looking at the gauge now and found a PO had epoxied this wire lug in place.  I can't imagine what this rig is supposed to be doing.
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With factory wiring, the hand will peg all the way to the top right at startup. The end of the hand will snag into the soft shield and hang at the top. Looks like they glued in the terminal as a bump stop to prevent it from hanging.
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fierofool
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FEB 07, 04:44 PM
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Eliredandblack, come join us this Saturday the 15th, at The BBQ Place on Powder Springs Road. Georgia Fiero Club meets at 10 AM.
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fierofool
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FEB 07, 04:52 PM
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| quote | Originally posted by PhatMax:
I could be wrong but since it’s really just a switch, not sure it matters which side the wires are on….no ? |
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It does make a difference which wire is plugged to which terminal on the sending unit. One terminal for the light is an ON/OFF contact. The other terminal for the gauge is a variable resistor. You can determine which wire is for what function by inserting a paper clip in the connector and grounding it to the engine.
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theogre
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FEB 08, 01:50 PM
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⚠️ Above chart is for ECM temp sensors.
Gauge sender uses different thermisistor and values won't match ECM charts. And Most Gauge Senders ground to the engine...
Gauge coolant sender...
1365Ω at 100°F(38°C)
55Ω at 260°F(127°C)
From any Fiero FSM
If you have Arduino kits, old dead things, etc, use the pots to dial in those exact value to test the gauge and wire to the sender.
Or buy RD gauge testers.
If gauge reads wrong...
Many things can make any dash gauge lie to not working.
Even if gauge wiring is good, iffy grounds nearly anywhere in the car can still make problems.
Some Examples:
Most Gauges have Resistors on back that's never covered in FSM Alldata and more. Careful removing/tighten the nuts holding them often cleans oxides etc and work better. Using Deoxit etc may help too.
Dash back and SS clips often get crap connection over time too.
removing/installing the Big plugs to the dash back, the board copper often have problems and can short out.
Any crap ground in the engine bay or the cabin causes gauge errors.
Gauge may read 100% accurate but you compared to whatever just think is "Wrong."
Even Sender/sensors near each other can read different temps because of coolant flow and exact design/manufacturing of each part.
Plus Fiero temp Gauge and sender was never to be very accurate and why Most cars and truck have same setup but No Numbers on the gauge.
Even Most new cars w/ dash gauges under ECM/BCM control don't numbers on temp gauge and even oil pressure gauge because idiots go into a panic easy and claim Warrant or worse for nothing wrong.------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)
The Ogre's Fiero Cave
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Notorio
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FEB 09, 12:12 AM
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| quote | Originally posted by theogre:
⚠️ Above chart is for ECM temp sensors. ...
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Dang, too bad I had already ordered $5 worth of resistors to check the calibration on the gauge.
Is it really correct that the temperature gauge was mislabeled by GM from 84-88 and they didn't fix that?? Well, I guess when you consider that the temp gauge & temp light wiring were reversed, and the service manual was wrong, for 84-88 without them fixing it, who knows what else was passed over?? Sheesh. 
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theogre
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FEB 09, 02:53 AM
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You already have same data in pic 3 & 4 in top post and then you posted wrong chart...
Many Arduino and other kits have resistors and trim pots can make test resistors.
Or take them out of dead old things.
Quick test is just use them in engine bay.
Then on dash back. see https://www.fiero.nl/forum/Forum2/HTML/138175.html
That should tells a lot in minutes even if need to remove the dash back plastic.
even if gauge is "accurate," senders can have 1% 5% or way more tolerance and gauge can read exact to x% higher or lower.
And that's on top of location, coolant flow, and more.
Dash gauges only are ballpark guides to being safe to having problems.
You never trust them for real data because so many things make them lie.
Fuel and oil pressure often does same. even more because dealing w/ 0-90Ω in a lot of GM and other brands.
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ArthurPeale
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FEB 09, 10:01 AM
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| quote | Originally posted by fierofool:
It does make a difference which wire is plugged to which terminal on the sending unit. One terminal for the light is an ON/OFF contact. The other terminal for the gauge is a variable resistor. You can determine which wire is for what function by inserting a paper clip in the connector and grounding it to the engine.
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I performed the fix back during the Summer months.
Every time I start the car, I get a kick that it was wrong from the factory, and just...works...now.
Turn the key, temp light comes on, gauge does not peg.
it's the little things in life that are so satisfying.
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Notorio
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FEB 28, 08:53 PM
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So to wrap up things up, I tested the wiring (which was good) and the Temp Sensor and the Oil Pressure Sensor (which were bad, apparent victims of the 12v-to-gnd mishap.) Replacing them solved the two gauge problems.  ...
But, in the process, now the Speedometer and Odometer don't work. I found some posts on how to check the VSS itself, but before I pull that out I'd like to know if this left-over 18-pin plug should be attached somewhere. I don't remember where that was when I took the lower dash apart to check the Temp and Oil Pressure wiring. I have already disconnected / reconnected the plug going into the Back of the dash panel, but am a little concerned about the flimsy thin-film plastic strip wiring that is on there.[This message has been edited by Notorio (edited 02-28-2022).]
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Notorio
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FEB 28, 08:56 PM
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For some reason I can't post the image above via Edit so trying separately here ...
ok, it just took FIFTEEN minutes to reboot this old garage computer. Trying AGAIN to post the picture using the Upload Image button ...
And nothing ... tried from Chrome, tried from Edge. Gonna give up on this for now. 
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Just tried 'upload image' from another computer and same result, no upload. Is anyone else having this problem??
And now success! I just used the old PIP app to post it. Incredible.
 [This message has been edited by Notorio (edited 02-28-2022).]
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theogre
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FEB 28, 11:29 PM
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Speedo has nothing to do w/ dash back plugs.
the plug is on bottom[This message has been edited by theogre (edited 02-28-2022).]
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