Idle Speed & Radiator Fan Iss

[johnbear]

I've just spent the afternoon trying to fix an odd idle problem. The idle on the Griffith is fine until the cooling fans kick in. As soon as the fans come in the idle speed increases to 1500rpm!. It's a bit of an odd configuration as it's running Rover twin Plenums. Any suggestions would be appreciated.

[Ant.]

The 14cux does have an input which was used to tell it when the heated rear window was switched on and increase the idle accordingly to compensate.
Tvr used that input when the fans switched on. Surprised it raises the revs that much though, so maybe a problem with the stepper motor ?

[RichB]

Interesting; didn't know that. Why would they do that? Does the increase in draw on the alternator put a load on the pulley which slows the engine down?