[928uk] S4 Overheating - Temp Sensor Operation

[Paul R Smith]

No, S4 uses high refrigerant pressure to indicate need for fan.
S uses high refrigerant temperature.

All need a minimum pressure before they run the compressor.

Smiffy

On 05/06/2024 13:30, Ben Hodges wrote:
> Hi Jon - I think that’s a temp switch? The pressure switch is there to 
> stop the compressor clutch kicking if there’s no gas/pressure in the 
> system.
>
> On Wed, 5 Jun 2024 at 13:05, Jon Holdsworth via 928uk 
> <928uk at lists.928.org.uk> wrote:
>
>     Short circuit the pressure switch on the top of the receiver dryer
>     canister and the fans will come on MAX when the AC button is
>     pressed in. This seems to be irrespective of internal or external
>     air temperature.
>
>     Jon in Sydney
>
>     -----Original Message-----
>     From: 928uk <928uk-bounces at lists.928.org.uk> On Behalf Of Paul R
>     Smith via 928uk
>     Sent: 05 June 2024 21:34
>     To: Paul <ukkid35 at gmail.com>
>     Cc: 928uk at lists.928.org.uk
>     Subject: Re: [928uk] S4 Overheating - Temp Sensor Operation
>
>     I have never noticed fans coming on with a cold engine just
>     because the A/C is switched on. Does yours do that now?
>     (I can't check on my GT now as it currently has zero A/C pressure).
>
>     Smiffy
>
>     On 05/06/2024 11:58, Paul wrote:
>     > Here's the section that mentions using the aircon to force the
>     fans on:
>     >
>     > *TROUBLESHOOTING THE COOLING FANS (‘87 AND UP CARS)*
>     >
>     > Turn the ignition switch on, but don’t crank the engine. Turn
>     the A/C
>     > on, with the blower on speed 2. Both cooling fans should run at
>     low speed.
>     >
>     >
>     > I had a problem yesterday, thankfully resolved now - I don't
>     have the
>     > original plugs on the ends of the fan leads which fooled me into
>     > thinking I'd connected the cables when in fact I hadn't
>     >
>     >
>     > I used the email from earlier because it had some useful info at
>     the
>     > beginning, I didn't notice that it had been truncated
>     >
>     >
>     > Paul
>     >
>     > 87 S4 Manual
>     >
>     >
>     > On Wed, 5 Jun 2024 at 09:54, Paul R Smith via 928uk
>     > <928uk at lists.928.org.uk> wrote:
>     >
>     >     That's a big document, and I can't see what you refer to.
>     >     But I'm a bit confused, the email you are replying to is from
>     >     2007. Do
>     >     you have a current problem, or are you pre-emptively
>     checking your
>     >     fan
>     >     system?
>     >
>     >     Smiffy
>     >
>     >     On 05/06/2024 08:17, Paul via 928uk wrote:
>     >     > For anyone who needs an easy to read diagnostic guide, this is
>     >     invaluable
>     >     >
>     >     > https://www.928gt.com/T-WallyHVAC.aspx
>     >     >
>     >     > However, the method he advises to force the fans to run
>     does not
>     >     work on my
>     >     > car, probably because my aircon has lost pressure and is not
>     >     operational at
>     >     > the moment
>     >     >
>     >     > Therefore I made this by taking an old temp sensor,
>     breaking off
>     >     the brass
>     >     > section, and twisting the wires together
>     >     >
>     >     > Then I removed the connector to the radiator temp switch and
>     >     plugged it in
>     >     > there, this forces the fans to run with the ignition on
>     >     >
>     >     > https://thumbsnap.com/i/JCzAYETX.jpg
>     >     >
>     >     > Paul
>     >     > 87 S4 Manual
>     >     >
>     >     > On Mon, 21 May 2007 at 11:45, Paul<ukkid35 at gmail.com> wrote:
>     >     >
>     >     >> Quote from EuroCarParts for:
>     >     >>
>     >     >> Rad Sensor (Fan Switch)
>     >     >> Temp Sensor (I or II - not known)
>     >     >> Thermostat
>     >     >>
>     >     >> £90, but at least they are all in stock. I won't know
>     which temp
>     >     >> sensor they have, Temp I or Temp II, until I see it though.
>     >     >>
>     >     >> Not exactly a bargain, but it's no fun when they're faulty.
>     >     >>
>     >     >> Paul
>     >     >> 87 S4 Manual
>     >     >>
>     >     >> On 20/05/07, Paul<ukkid35 at gmail.com> wrote:
>     >     >>> No sign of it escaping from the overflow hose, but I hope
>     >     that's where
>     >     >> it's
>     >     >>> going - where else could it go?
>     >     >>>
>     >     >>> Switching the aircon on seems to keep the temp under
>     control,
>     >     but there
>     >     >> was
>     >     >>> an initial very high reading after about 4 mins driving,
>     which
>     >     then
>     >     >> dropped
>     >     >>> to normal, I'm guessing was when the thermostat opened -
>     >     perhaps there
>     >     >> was
>     >     >>> an air lock.
>     >     >>>
>     >     >>> I'm tempted to replace Temp I, Temp II, the Rad sensor
>     and the
>     >     Thermostat
>     >     >>> all at once. In the past I would have been more frugal, but
>     >     for once I
>     >     >> can
>     >     >>> aford to be a bit more extravagant.
>     >     >>>
>     >     >>> Paul
>     >     >>> 87 S4 Manual
>     >     >>>
>     >     >>>
>     >
>