How to repair a dodgy Idle speed control valve - NA B6

[StillIC]

Interested parties,

I have an ISCV from an NA B6 which does not work, but the resistance value reads OK (12.9 ohms, which is within tolerance). It appears to be seized. I have tried various de-seizing, penetrating sprays and lubricants without luck.

I want to pull this thing apart, without damaging it preferably, but am failing so far.

Has anybody pulled one of these apart and successfully repaired it, and, if so, how do I do it? Before you ask, yes I have read the page on miata.net, but it only shows the parts without explaining the disassembly procedure.

TIA.

[gslender]

How are you confirming it isn't working?

G

[project.r.racing]

i'd just replace it.

[StillIC]

quote="gslender"]How are you confirming it isn't working?

G[/quote]

I have applied 0 to 12 volts across it using a bench top power supply, with no movement whatsoever observed. I have also applied a constant 12V and varied the current from 0-maximum draw, again with no movement observed.

I figured that with only a 2 pin input, there was nothing fancy about the input signal required, e.g. it is not a stepper motor, just a simple DC motor working against a spring.

[gslender]

It doesn't work that way. It needs a PWM feed to move. I'm unsure what apply 12v to it would do, and would expect it to either fully move or not move at all, but that wouldn't be a good test.

G

[StillIC]

Sure, Pulse Width Modulation will allow fine positioning of the motor, but application of a constant voltage is simple a 100% on signal, 0% off signal, which should give a fully open response. Just as application of a 100% off, 0% on signal gives no movement at all. The PWM simply gives adjustability between these two extremes.

I have no response at all. 0% on and 100% both result in the same position.