I have a '88 GT with a 3800 SC Series II from a '99 Regal GS donor car. It is an older swap, 10 years or more, that I purchased last year. The swap builder also installed the '99 Regal gauge cluster, which looked very bad, so I am replacing it with stock Fiero gauges.

I am trying to get the Temperature gauge working correctly. I am thinking the '99 3800 SC engine may use both a Temperature Sender/Sensor for the gauge, & Engine Coolant Temperature (ECT) Sensor for the ECM.
The only sensor that I have found so far is on the rear (trans. end) lower left (bulkhead side) area of the intake manifold, that has a Green, Black & Yellow wire harness connected to it. It is a round 3-Pin sensor.

Does anyone have photos of these two sensor locations for the Series II 3800 available that you can share?

Thank you for the help on this one.

[This message has been edited by hdryder (edited 10-28-2015).]

GM makes a three pin ECT sensor that also provides a gauge output. Some 3800's use them and others do not but both sit in the same spot and have the same threads. The ECT sensor sits in the location at the front top side of the engine block near the transmission. One pin is for ground, the other feeds the PCM and the center pin drives the temperature gauge. If you currently have a temperature gauge just pick up the center wire from the ECT and route it to the Fiero gauge.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

Dennis, thank you for that info. That works out well for what I just found on my car with the '99 3800 swap.

The Engine Coolant Temp. (ECT) Sensor I found is actually a round 3-pin connector with a short 3-wire harness that connects into a 2-wire sub-harness on the engine harness. The short 3-wire harness has a Black, Yellow & Green wires. The 2-wires it plugs into are just the Black & Yellow. Also the Fiero engine harness at the C500 connector have all been trimmed off and sealed, but leaving several inches on each wire, so I plan to run the Green (ECT) Sensor wire to the C500 connector C2 Dk Grn/Yel wire which feeds the Temp. Gauge.

What I would like to know now is what kind of input do I need for the C500 connector D3 Dk Grn wire for operation of the "HOT" Temp Warning Ind. Lamp?
Do you think that same Green wire from the (ECT) Sensor can feed the D3 "HOT" Temp. Warning Ind. Lamp?

Thank you again for the help on this one.

The ENGINE HOT signal comes from the ecm. Not sure which pin on the ecm. I suppose it will vary with which ecm you are using.

DF

quote Originally posted by Dave E Bouy: The ENGINE HOT signal comes from the ecm. Not sure which pin on the ecm. I suppose it will vary with which ecm you are using. DF

Dave, thank you. I will check that out for the '99 Regal GS ECM used for the swap.

quote Originally posted by Dennis LaGrua: GM makes a three pin ECT sensor that also provides a gauge output. Some 3800's use them and others do not but both sit in the same spot and have the same threads. The ECT sensor sits in the location at the front top side of the engine block near the transmission. One pin is for ground, the other feeds the PCM and the center pin drives the temperature gauge. If you currently have a temperature gauge just pick up the center wire from the ECT and route it to the Fiero gauge.

Thanks Dennis, on my new swap, a 2002 GTP into an 84 MT the temp needle disappears up above the gage. As the engine heats up to operating temp i get 45C on the gage (should read 90C) When i shut of the car the temp stays near 45C but when i restart the car the needle disappears again.

jon

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Astronomy says we will find a coded signal from outer space. Then we'll KNOW that life exists there, for coded signals aren't by chance.

Biology says there are coded genetic signals in every cell, but we KNOW that no intelligence created life.

I'm the original owner of a white ' 84 2M4 purchased Dec 10, 1983 from Pontiac. Always garaged, no rust, 3800SC, 4-wheel drifts are fun!

quote Originally posted by longjonsilver: Thanks Dennis, on my new swap, a 2002 GTP into an 84 MT the temp needle disappears up above the gage. As the engine heats up to operating temp i get 45C on the gauge (should read 90C) When i shut of the car the temp stays near 45C but when i restart the car the needle disappears again. jon

Make sure that the center pin of the sensor goes to the temperature gauge. Could also be a wiring or gauge problem.