Under Reading coolant gauge on I5 100

[rob hod]

    Hey Huw,

    Thanks for very speedy response on that one!,

    My (un)trusty Haynes manual also says brown yellow for that wire on two
diagrams that aren't really my car, i.e.  1984 200T and 1989 2.3NF. I don't
put a huge amount of store by these diags as the later one seems to miss out
the overheat sensor entirely and lists a device under the key D2, which
don't exist, its only when you go back to the 200T diagram that you realise
they mean G2 (temp gauge sender). In other words its all a bit slapdash.

    The pinout you quote agrees with my findings and all other colour codes
check out fine as well.

    Thanks for the ohmages as the Haynes don't mention them. I can have fun
with multimeter and resistors now.

    Cheers Rob.

    PS I was looking at getting a spare FPR for my car, just for backup as I
see from the list they fail from time to time.
    However when I found the dealer wanted GBP 61 for one I thought I may as
well just make up a jumper lead for that contingency. Am I right in thinking
your site has tips on that? I looked a while back and couldn't immediately
find it.


----- Original Message -----
From: Huw Powell <audi at mediaone.net>
To: rob hod <rob3 at hod3.fsnet.co.uk>
Cc: <quattro at audifans.com>
Sent: Monday, November 05, 2001 12:26 AM
Subject: Re: Under Reading coolant gauge on I5 100


> Everything you say sounds accurate.  It seems like you have diagnosed
> either poor wiring or a faulty gauge or regulator (gauge volt reg that
> is), since shorting that wire should peg the gauge.  Of course I'm
> looking at the wrong year in a copied Bentley and the wire should be
> brown/yellow according to it.  It shows no brown/black wire though.
>
> the pin in question is the upper right when you look into the wiring
> connector with the little "V" indent at the bottom.
>
> 660 ohms should put it at about 1/3 scale, 50 ohms at about 2/3, where
> it says "H".  How good is that ground you are making?
>
> rob hod wrote:
> >
> >     Wonder if anyone can help me out on this. Patient is an '88 100 with
2
> > Litre I5 engine (RT).
> >
> >     The problem is that the temp gauge is under reading. I have a sneaky
> > suspicion the thermostat has been removed as the car generally runs
cool,
> > I'll be checking this next weekend.  However there's no doubt that the
gauge
> > reads under, for example the car is running up to a reasonable temp.  in
> > summer but rarely reads more than 1/4, and for further proof the
radiator
> > fan cuts in with the temp gauge reading around 1/3rd f.s.d.
> >
> >     Now the specifics of my query are this, The wiring diagram mentions
an
> > 'electronic thermoswitch, and the wiring on the car suggests that this
is a
> > brass fitting with a four pin electrical connection under the upper rad
hose
> > connection to the head.  Before I bought the car I think this sender was
> > replaced as I have an invoice for Pn 034 919 369C "Temp sender" I wonder
if
> > a slightly wrong part was used? If I take a lead from the brown/black
wire
> > on the socket and earth it with the engine off but the ignition on I get
a
> > gauge reading of around 2/3rds. Anyone know if this part is indeed the
> > 'electronic thermoswitch mentioned in the manual?
> >
> > I have a theory that I may get a slightly higher reading with the engine
> > running, but presumeably the voltage stabiliser should limit that to a
fair
> > extent.
> >
> >     In addition there is a small sensor fitted to the top of the hose
outlet
> > fitting which also has a brown/black wire going to it.
> >     Anyone know if this is the 'overheat' sensor or the actual gauge
sensor
> > ?
> >
> >     By the way the fuel gauge appears to be working and calibrated
properly.
> >
> >     Thanks in advance
> >
> >     Rob Hod
>
> --
> Huw Powell
>
> http://www.humanspeakers.com/audi/
>
> http://www.humanthoughts.org/
>