4kq coolant temp warning light / dash temp gauge and sender diagnosis

Jpinkowish at aol.com Jpinkowish at aol.com
Sun Aug 11 15:13:41 EDT 2002

In a message dated 8/10/02 11:07:42 PM EDT, aaron at eurekalubricants.com writes:

> I've been getting this blinking light pretty regularly.  It will either
happen when
>  I'm cornering hard, accelerating hard (through a couple gears), and running
>  at 75mph+ (for a couple minutes).

< snip >

Aaron and other 4kq/CGT owners,
I go through this too, and my coolant level, either at operating temp or at
fully cool, appears OK.  As many other know, the level indicator is often
super sensitive.  So, just add a little more coolant(1 cup), and Mr.
Blinky-Blinky should go avay.  Don't forget to fully open the heater valve
before doing this.

>  My coolant temp gauge usually hovers just above the 3rd hash mark from the
>  top, which I've been told is high.  However, it's always done this in the 6
>  years I've owned the car.  My oil temp gauge will often get up around 130
>  degrees when I'm running 75mph+ on the highway.  Is this abnormal?  This
>  temperature seems to be higher than what it used to be.  I always
>  the oil temp hovering around the lower hash mark (~100 degrees) at all
>  times.  Any ideas?

Several observations:
--renew the ground connections in that area.  I can get my oil temp gauge to
drop 2-3 hash marks just by turning off all the lights.
--Bentley ch. 90.20 gives you coolant temp sender resistance vs. engine
coolant temp.  Plot the graph, run your car until the fan kicks on(that's
90-95degC), and measure the output resistance of the sender(terminal on the
sender that goes to the blue/brown wire in the loom and the other to ground).
 See where you are on the graph; that tells you if the sender is OK.
--if the sender tests OK, use a resistance substitution box to simulate
different coolant temps.  calibrate the resistance box to a digital VOM, and
connect the box to the blue/brown lead and to ground.  Turn ignition switch
only to activate the electrics, and then switch the box through the
resistance range given in Bentley ch.  90.20.  You should be able to drive
the gauge to the top.  Remember that there is a lag in the gauge response to
changes in the resistance that you give it.
--if both the gauge and sender test OK, then the little 10V power diode that
feeds the temp and fuel tank level gauges is geflooey.  Here's where you can
get 'em:
Message: 8
From: "John Larson" <j.d.larson at verizon.net>
To: <quattro at audifans.com>
Subject: Re: Instrument cluster voltage stabilizer
Date: Mon, 22 Apr 2002 17:43:22 -0700

#171 919 803.  List $11.20, I sell'em for 7 bucks delivered to any US
address.  Shoot, I'll send'em to Canada too, for the same price.



Jan Pinkowish
'85 4ksq
Bristol, CT

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