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| Temp gauge doesn't go past 100 (Page 1/2) |
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WaterInYuhDish
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OCT 25, 07:20 PM
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I have an 87 GT with the 2.8 and The gauge doesn't peg to the right like the common issue I've read and seen. The needle barely moves after turning the key to the on position, from there the temp gauge needle NEVER goes past 100°
I've tested the connector by grounding each pin and confirmed that the dummy light came on for one pin and the gauge pegged when grounding the other pin. I replaced the sending unit and still nothing has changed.
TIA!
Edit:
Found out a previous owner had the ecm sensor and connector were installed where the gauge sending unit is supposed to be. Will this not work? Do I need to revert back to the original sending unit? I also just tested the connector for voltage and got 12v. I've read it's suppose to be 5v! What does this mean?[This message has been edited by WaterInYuhDish (edited 10-26-2021).]
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eti engineer
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OCT 25, 07:55 PM
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| quote | Originally posted by WaterInYuhDish:
The gauge doesn't peg to the right like the common issue I've read and seen. The needle barely moves after turning the key to the on position, from there the temp gauge needle NEVER leaves 100°
I've tested the connector by grounding each pin and confirmed that the dummy light came on for one pin and the gauge pegged when grounding the other pin. I replaced the sending unit and still nothing has changed. I'm wondering if maybe a previous owner reversed the wires of the connector? Is that worth doing a splice and crossing the wires?
Other than that I've gathered that it would be an issue within the gauge itself inside the dash. Is there anything else I've missed that could be causing this?
TIA! |
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I'm originally from Logan, Utah. I just recently visited out there. I need to move back. I am not a fan of Californication!!!
As cool as it is in Utah right now, I am wondering if your thermostat is stuck wide open or missing. I just rebuilt the whole back end of my car including the engine (done by a builder for a warranty) and I put a 160 degree T-stat in it. RIght now, as cool as it is here in CA, when my engine is idling in the garage, it will not get above 130 degrees and it takes a while to get there. I wanted to test my fan switch to see if it works, but I had to do it a different way. Do you know where the thermostat is? Firstly, do you have a V6? I don't know where it is on the 4-banger. If you do, there is a piece that looks like a radiator cap on the engine. This is actually the cap for the T-stat housing. With the engine being cool, turn the cap and underneath you will see what appears to be a handle. This is a handle to allow you to pull the thermostat out. If you don't see this, someone removed the stat to keep the car running cool in the hot Utah summers and never replaced it.
Your gauge could still be a culprit, but this is an easy quick check just to make sure that you have a thermostat. Check it when you pull it. Cold, it should be fully shut. If it didn't open, once it got hot, you could have an overheating issue, which you don't. If you want, you can put the stat in a pot of boiling water and see if it opens just to ensure proper operation. Good luck...
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Xenoblast
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OCT 25, 08:17 PM
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Buy an appropriate resistor that matches one of the resistance values in this chart, near a 145 ohms resistor would probably be best, and ground one of the wires to ground with the resistor in between. If it is not close to the temp it shows in this graph for the given resistance, then either the gauge is bad or the wiring to the gauge is bad. Also keep in mind that one of the wires is for the overheating light, and the other the actual gauge.
Also make sure you are using the right sensor. The correct one is the right one
Also make sure you dont put any teflon tape on the threads of the sensor. I am pretty sure it grounds through the housing but I could be wrong[This message has been edited by Xenoblast (edited 10-25-2021).]
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WaterInYuhDish
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OCT 25, 08:41 PM
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The ecm sensor has been being used where the gauge lamp sensor should be... Lol I even talked to Napa about the difference and they still sold me the wrong part. Haha I really hope this is it.
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Xenoblast
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OCT 25, 08:49 PM
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| quote | Originally posted by WaterInYuhDish:
The ecm sensor has been being used where the gauge lamp sensor should be... Lol I even talked to Napa about the difference and they still sold me the wrong part. Haha I really hope this is it. |
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Yep, thats actually exactly what happened to me. Previous owner even changed the connector for it to the ECM version. Im pretty sure the fiero store sells the connector if you need it.
Edit:
heres the connector
https://www.fierostore.com/...px?s=65488&d=172&p=1[This message has been edited by Xenoblast (edited 10-25-2021).]
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WaterInYuhDish
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OCT 25, 09:26 PM
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| quote | Originally posted by Xenoblast:
Yep, thats actually exactly what happened to me. Previous owner even changed the connector for it to the ECM version. Im pretty sure the fiero store sells the connector if you need it.
Edit:
heres the connector
https://www.fierostore.com/...px?s=65488&d=172&p=1
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I'm going to take a wild guess and say that there aren't any stores that carry those in stock. So the fiero store is my only option?
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Mark_j
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OCT 26, 12:59 AM
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| quote | Originally posted by WaterInYuhDish:
I'm going to take a wild guess and say that there aren't any stores that carry those in stock. So the fiero store is my only option? |
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Rock Auto carries them. Standard Motor Products PN TS168.
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WaterInYuhDish
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OCT 26, 11:29 AM
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Something I just tested was the connector for voltage and got 12v. I'd read it's suppose to be 5v! What does this mean? I also found where they spliced the new connector head in, could the 12v mean they flipped the splice and it's reading weird or that there's something else wrong?
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theogre
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OCT 26, 04:48 PM
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for top post just sound like someone already did some version of gauge fix to stop slamming it when starting. (Actual issue is Bulb Test position just before you turn the key fully to start.)
Three or more ways can do that and not all will fix the temp Light to turn on during starting. (Assuming that isn't blown or otherwise dead.)
As to "Not Accurate..."
Most temp dash gauges are Never accurate w/ numbers on them and why most have no number but red zone and maybe C & H.
Fiero have same iffy gauge setup as others just someone at GM put number on it.
Then on top of that, Any dash gauge can lie for many reasons and you trying to fix that is often a waste and never find what's wrong.
That even when the Gauge and Sender are 100% Good.
1 iffy ground anywhere in the car is often enough to make them lie. Oil Pressure and Volt Meter often have same problem.
Even the dash itself have several connections to the gauges that must be 100% good but rarely are on Decades old car...
Big plugs to back of dash that gets dirty etc.
Then have SS spring clips that have similar problems connecting to the dash "board" and Gauge bolts.
Gauge bolts and nuts and resistor can have same problems even if gauge and resistor are OK.
Gauges w/ resistors on back, the resistor can change value over time for many of same reasons making gauge setup to change and read off.
That's Why most ECM sensors have 2 or 3 wires those being 5V, Ground and Sensor Out.
Even "one wire" O2 sensor only generates ~ 1V max actually uses 2 wires w/ 1 Tan "ground" bolted to the bell housing on most GM cars.
Warning: Many Charts showing Ω vs Temp are for ECT for ECM and NOT for the Dash Gauge.
While both can use NTC Thermistor, the Ω Values for each are way different. ECM needs a different Resistivity Curve to cover Way Below 0°F to near 300°F to run the engine right. ------------------
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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Xenoblast
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OCT 26, 05:16 PM
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| quote | Originally posted by theogre:
Warning: Many Charts showing Ω vs Temp are for ECT for ECM and NOT for the Dash Gauge.
While both can use NTC Thermistor, the Ω Values for each are way different. ECM needs a different Resistivity Curve to cover Way Below 0°F to near 300°F to run the engine right.
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Thats probably true but I can vouch for this list, I used it when I was diagnosing my temp sensor and it was spot on atleast for 220 degrees
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