cooling fan operation
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Joined: Jul 2002
Posts: 524
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From: Port Charlotte Fl
cooling fan operation
ok, need a little help here. the primary cooling fan has been jumpered to ground since i purchesed it (87 coupe ), today i was making numerous little repairs, so i decided to remove the jumper to ground, this of course had the desired effect of NOT having the fan run at all times when ign is on, i confirmed that the ECM appeared to be back in control of the fan by putting ECM into diagnostic mode, and fan started as expected. now here is the problem. in normal operation the ecm turns the fan on at what temp? i let temp rise to 220 indicated and no fan primary or aux. (HD cooling option )
Also in what little info is given by the haynes manuals it looks as though the TCC is also controlled by the same ground as the fan relay ( dk green white stripe) could anyone confirm this for me ( i either dont get TCC lock up, or it is continusly locked, which (while driving it with the fan jumper removed the car seemed far more aggressive in acceleration) i tend to suspect)
Also in what little info is given by the haynes manuals it looks as though the TCC is also controlled by the same ground as the fan relay ( dk green white stripe) could anyone confirm this for me ( i either dont get TCC lock up, or it is continusly locked, which (while driving it with the fan jumper removed the car seemed far more aggressive in acceleration) i tend to suspect)
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Joined: Dec 2000
Posts: 90,675
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From: SE NY
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Re: cooling fan operation (LarryK 87)
That's about right for a stock chip; the General set up our L98s to realy run rather hot.
If you would like the engine to run cooler, install a lower temp T-stat & a matching aux fan switch and then wire it turn on the main fan. See my C4 Tech Tip on how.
The fan relay has nothing to do with the TCC. The ECM controls the fan but has no feedback from it.
You can check the TCC status by putting a test light between pins F & A on the ALDL. When the ECM issues the lockup command the light will go out, otherwise it will be lit.
BTW, the ECM cannot lockup the TCC in 1st gear due to A4 design. With a stock TC you may not be able to notice when the TCC locks up. However, even if the ECM is sending the lockup command it may not be locked, so you can try this easy test:
-while rolling along in 4th gear at about 1,000 or 1,200 rpm touch the brake pedal to unlock the TCC and then tap the accelerator. If unlocked you should see the tach jump to near 1,500rpm.
-Then repeat the test without touching the brake pedal; if the TCC is locked the tach won't jump noticibly.
If you would like the engine to run cooler, install a lower temp T-stat & a matching aux fan switch and then wire it turn on the main fan. See my C4 Tech Tip on how.
The fan relay has nothing to do with the TCC. The ECM controls the fan but has no feedback from it.
You can check the TCC status by putting a test light between pins F & A on the ALDL. When the ECM issues the lockup command the light will go out, otherwise it will be lit.
BTW, the ECM cannot lockup the TCC in 1st gear due to A4 design. With a stock TC you may not be able to notice when the TCC locks up. However, even if the ECM is sending the lockup command it may not be locked, so you can try this easy test:
-while rolling along in 4th gear at about 1,000 or 1,200 rpm touch the brake pedal to unlock the TCC and then tap the accelerator. If unlocked you should see the tach jump to near 1,500rpm.
-Then repeat the test without touching the brake pedal; if the TCC is locked the tach won't jump noticibly.
