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Discussion Starter #1
96 4.6 Cougar ~70K miles.
When in traffic at idle and the cooling fan (radiator fan) kicks on the car shakes for a couple seconds then smooths out, there's a slight dip in RPMs. I notice when the A/C cycles also, but much less. It's like the fan kicking on draws a ton of current and loads the alternator and the engine has to catch up. My 97 did something similar and never really though much of it. I've done the big 3 upgrade on the wiring and it still does this. It's like a delay for the ECU to react to the load. Any other experience this? Is it normal? Should I look into something here? Thanks.
 

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When the AC comes on, the highspeed fan comes on; it the lowspeed fan is affecting it more, the fan motor may have a problem.

You need a dc-capable clamp on ammeter to diagnose that; low will draw more current than hi.

It's rare, but I've seen it on other cars.
 

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had that problem it was a simple fix for me. it ended up being the clutch on the ac unit that was making more of a draw on the system I replaced the ac clutch which was a pia because of the limited space on the location on trying to get to the clips. once that was replaced it was good to go
 

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What does the RPM get pulled down to? Just wondering if it's something related to the IAC.

Al
 

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Discussion Starter #5
It's hard to tell. Most of the time I'm not watching the temp gauge or the Tach, I know the tach does drop, but really not sure what it drops to. I'm trying to find a DC amp clamp to borrow and see if the fans are pulling too much current when they spin up.
 

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Look at the voltage reported by the eec; that's what's dropping. :)


Check your wiring carefully; this is getting more common. :)
 

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Discussion Starter #8
I'm sure corroded wires are still a potential. I tested the battery and it was weak, I've since replaced it and that rough idle when the fan kicks on is gone. I believe the rough idle was caused by the alternator needing to catch up to the sudden current draw of the fans spinning up and since the battery was weak the full load was on the alternator.
 

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If the voltage hits 8V, even for an instant, the eec turns off. :)
 
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