Date: Sat, 10 Jul 2021 21:18:15 -0700
Reply-To: Ryan Cresawn <jrcresawn@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Ryan Cresawn <jrcresawn@GMAIL.COM>
Subject: Re: low idle when AC compressor is on
In-Reply-To: <4b4428d0-5186-bd2c-876a-abf9a7341d90@cox.net>
Content-Type: text/plain; charset="UTF-8"
I spent some time studying the wires connected to the compressor, testing
them for continuity, and studying the Bentley which I have not found very
helpful with this wiring issue. I admit I could be looking in the wrong
sections. I looked in the fuel injection section beginning on 24.52 and the
air conditioner section beginning on 87. The fuel injection section section
defines the test procedures Ken identified. With the A/C off the engine
idle is near enough to the target 880 +/- 50 rpm for me to believe the
tests in the fuel injection section of the Bentley are not relevant to me
at this time. I think it's important to recognize that this low idle
problem followed the replacement of the compressor and is present only when
the compressor is on.
Now to the wiring. All my continuity tests results were positive. In my
earlier email I described the wires based on memory, which is not ideal.
Now that I have photos of the wiring I can describe it with more detail.
The compressor has two wires attached to it which connect to a plastic
two-conductor plug. I assume these two wires are positive and negative to
engage the compressor clutch. Maybe that is engaged by electromagnet. I
don't know. The other end of that plug has a Y on one of the conductors, so
one side of the connector has two wires and the other side has three. I
suspect the two larger conductors carry current and the third conductor
carries a signal to inform the engine to increase the idle when the
compressor has current applied to it. I tried to trace the signal wire but
it is bundle with other wires near the fuel injectors on the driver's side
of the engine. What I am calling the signal wire is cream with a black
stripe. Since I don't know where it terminates I have not been able to test
for continuity very far along its path. Where does this signal wire
terminate? Could I have a blown fuse somewhere that is causing this low
idle behavior?
Thanks,
Ryan
On Sat, Jul 10, 2021, 18:46 vw_van_fan_Mark <madvws@cox.net> wrote:
> The compressor clutch needs a control wire from the A/C wiring to turn
> the compressor on/off as needed.
> The wire I was talking about is an additional wire feeding over to the
> true fuel injection harness for idle speed control use.
> The wire over to the fuel injection harness connects to a thin
> white/green wire coming out of the injection harness under the ignition
> coil.
>
> Mark
>
> Ryan Cresawn wrote:
> > Thanks Mark. I see the single wire laying across the top of the
> compressor.
> > The end coming from the fuel injection wiring harness is connected to the
> > end coming from the compressor. The two meet and lay on top of the
> > compressor. I suppose I could begin with a simple continuity test from
> one
> > end to the other. Does that seem like a good next step?
> >
> > Ryan
> >
> > On Sat, Jul 10, 2021, 10:31 vw_van_fan_Mark <madvws@cox.net> wrote:
> >
> >> A first step would be to check the wiring at the new compressor.
> >> VW runs a single wire from the fuel injection harness over to the
> >> compressor clutch so the injection system can know when the A/C
> >> compressor is loading down the engine.
> >> That is how the idle control system knows when to speed up the idle for
> >> A/C.
> >> They may have simply overlooked that signal wire to the idle circuit.
> >>
> >> Mark
> >>
> >> Ryan Cresawn wrote:
> >>> On July 6, 2020 I hired a shop to fix my factory AC in my '91 Vanagon
> >>> camper with 2.1l engine. The old compressor was leaking and the shop
> >>> replaced it. At 11.5 months into a 12 month warranty the AC wasn't
> >> cooling
> >>> well. I returned to the shop last week. They identified a refrigerant
> >> leak
> >>> in the compressor and replaced it under warranty. I picked up the
> Vanagon
> >>> yesterday and was told that I need to hire a shop to fix the low idle
> >> when
> >>> the compressor is on.
> >>>
> >>> I drove the Vanagon home and confirmed that when the compressor was
> >> running
> >>> the idle speed of the engine would drop from around 900-950 to about
> >>> 600-650. The engine did not stall but it felt like it was close to
> >>> stalling. How should I begin to troubleshoot this issue?
> >>>
> >>> Thanks in advance,
> >>> Ryan
> >>>
> >>
> >
>
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