When should the Main Fan com on?

My car has been over heating in traffic and I noticed while checking the transmission fluid that the longer it sat and idled teh higher the temp went...but only the smal fan came on..it went all the way up to the H and the big fan never came on. is this right? If not is it hard to jumper the fan and put a switch in the car to turn it on and off??
Thanks!

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Branden
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1979 Firebird Formula SOLD!!!
1988 Ford Thunderbird Turbo Coupe
1987 Ford Thunderbird LX 3.8L V6
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These cars are well known for their cooling problems. My 88 had the same prob that you are describing. I went to a switch for that fan. Check out the tech articles for a way to do it. Also - I went to the extra step of adding a mechanical temp guage just to make sure I was seeing what I was seeing....these cars are also known for their guage inaccuracies. If in doubt - stick a thermometer in the radiator neck.

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1988 TC 5 spd K & N, Bleeder. Next up - 3" downpipe to 2.5" duals

I finally got my fan working last night after replacing the ETC sensor. The gage does go up high - tell me how you installed the mechanical temp gage and where you connected it to the engine.

thanks

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NATO Paying Member
Here is my 1987 TC, Mean look - Glad to be here...
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If the smaller, driver side fan is coming on when the (inaccurate) temp gauge is about 3/4 of the way up the normal range, then the ECT is probably good.

Jumper the main (pass side) fan to the batt to be sure the motor itself isnt burned out. Of the motor is OK, I would bet on a bad fan relay in the IRCM.

Usually, the main fan comes on when the stock temp gauge gets about 1/2 way up.

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Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 20 psi, forced air intercooler, water injection, bypass valve, Ranger roller cam, subframes, etc., etc.. // 86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP nitrous, ignition, gears, suspension, etc., etc.... // 91 Escort: Bone stock winter car // 00 Windstar (wifes vehicle)