Ben Swann bswann at
Thu Jul 11 12:05:53 EDT 2002

Just adding 1 thing to what Huw says below.

For type 44/5000/200 with 2 wire ISV's, if you can blow through it, it is bad.  Some are worse than others, but if it passes any air -> BAD.

Three wire sensors do not adhere to this test.

With many too many flaky ISVs to stik a shake at!

> > Did you check your ISV with a 9volt or is there another method. WHen I
> > checked mine with a 9 volt it clicked. Is it supposed to do something else?
> For what it's worth, I just connected mine up in series with an ammeter to
> its connector, and put it where I could see it when I turned the key on
> and off.  I didn't have a 9V to hand ... I'd expect it to do more than
> click though (like close or open or do something...)

The ISV is driven on a "duty cycle" basis.  Some are two wire, some
three, some are closed at rest, some partly open.

In order to regulate the amount of air they allow through, the ECU sends
a constant stream of pulses, so the ISV sort of flips open/shut rapidly
- and makes a buzzing sound while doing it.  The width of those pulses
determines how much it is "open" versus "shut".

For this to happen two things are required: the engine must be running,
and the idle switch must be activated.

Huw Powell

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