John,

The connection to my AC Compressor is a White wire with a Green stripe, and
that color wire is not on your list.

Have I got the wrong wire? If not, where does this White/Green lead to if
not the Idle Controller.

Another question I have is WHY ME?!  Noooo, the question: This White/Green
wire has a connector on it, but the SD508 has no place to connect it, so I
have spliced into the AC Clutch on wire. Did any of the compressors come
with a cicuit built in with a diode or something, that I might be missing?

Kim

----- Original Message -----
From: "John Bange" <jbange@GMAIL.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Sunday, August 17, 2008 11:06 PM
Subject: Re: Idle Relay - Idle Valve match?

> > I did swap out the idle relay (controller) and it acted exactly the same
> > way.
>
> Heh. Well, then I betcha' THAT'S not it! Back to the drawing board...
>
> > Anyone (who knows these relays) think it might be a bad connection,
wiring
> > or a ground? I cleaned things up pretty well, but it's always possible
to do
> > more.
>
> I'd say that grounds are ALWAYS a suspect when you have weird
> electrical "Heisenbugs". That was one of the alternate theories that
> occurred to me today.
>
> > Why would it act up when it gets warmed up, but be OK when cold? It gets
the
> > signal from the temp sensor obviously.
>
> Indeed it does. The idle controller has the following connections:
> RED/BLK - power from ignition switch
> RED/WHT - power from fuel pump relay
> WHT/YEL - power steering high pressure switch
> BRN        - ground
> GRY        - coolant temp sensor
> RED/BLU - throttle valve switch
> WHT       - output to idle valve
> YEL        - output to idle valve
> GRN       - hall generator (RPM signal)
>
> The unit does indeed watch the coolant temp sensor, so that's always a
> possible source of trouble. A marginal connection could cause the
> trouble you describe. Excess resistance on the wire wouldn't affect
> the behavior of the idle controller when cold, as the temp reading
> starts off below whatever minimum "cold start idle adjustment"
> threshold there is; but as it warmed, the idle controller would
> perceive it as still being cold, perhaps even intermittently, causing
> excessive idle air bypass. A quick check of the gray wire should tell
> you if you have a resistance problem.
>
> Another possibility is a gummy idle valve not responding fast enough
> at certain ranges of opening, but that one seems unlikely.
>
> Probably not what you have going on, but worth mentioning: I once had
> a weird idle surge issue that turned out to be a loose distributor
> collar bolt, which I'd forgotten to tighten after adjusting the timing
> last. As I recall the distributor had "migrated" almost 10 degrees
> off...
>
> > Does anyone have a diagram of what's going on inside this relay?
>
> Well... I kinda have one, but it's not complete and what I do have
> ain't pretty! "Relay" is really the wrong word for it. It's actually a
> hand-tuned analog computer. It's the sort of device electrical
> engineers used to stay awake at night thinking about, before the
> advent of digital microcontrollers made solving such problems trivial.
> Imagine, if you will, designing a machine to keep an engine running at
> one of three or four predetermined numbers of revolutions per minute,
> with neither the ability to explicitly count revolutions, nor mark the
> passage of time. It's beyond me, it is.
>
>
> --
> John Bange
> '90 Vanagon - "Lastwagen"
> '90 Vanagon GL - "Wiesel"
>