Date:         Sat, 3 Aug 2002 15:08:12 -0500
Reply-To:     Bruce Nadig <motorbruce@HOTMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Bruce Nadig <motorbruce@HOTMAIL.COM>
Subject:      '87 GL Temp Gauge - Long
Content-Type: text/plain; format=flowed

While driving recently my temp gauge unexpectedly went to full hot and my
temp light started flashing. After a bit of diagnosis I am sure the van is
not overheating. Among other things, I disconnected the leads to the temp
sensor and attached an aftermarket VDO temp gauge. I ran the engine. Engine
ran fine and the VDO gauge confirmed that the van is not overheating.

I took an ohm meter to the connector that goes to the temp gauge. There is
good continuity from the ground terminal to ground. At ambient temperature
(engine cold) with the key off, there is about 350 ohm of resistance between
the yellow/red wire at the connector (goes to the gauge) and ground. Seems
to me that there shouldn't be any continuity.

As I was running the engine with the VDO gauge connected, the connector that
ordinarily connects to the temp sensor was disconnected. To my surprise, as
I ran the engine the factory temp gauge was starting to show that there was
heat in the engine. Slowly the needle rose until it got to the top and the
red light started to flash. This is all without the temp sensor connected to
the gauge. I consulted the VDO gauge to confirm that the engine was, in
fact, not overheating.

It seems to me that there is a short or malfunction somewhere between the
temp sensor and the gauge. With the key off I checked the continuity of the
yellow/red wire where it plugs into the instrument panel (connector T14,
position 6). From that position to ground there was no continuity.

I am guessing that the malfunction then must be in the instrument cluster.
The Bentley manual shows that there is something called a "Coolant Low Level
Control Unit." Somewhere this same yellow/red wire also connects to that. I
believe, but I'm not sure, that this control unit is built into the
instrument cluster. Might this be the component that is malfunctioning?

Because of this control unit and it's interaction with the coolant
temperature gauge and light, I put a jumper wire across the connector for
the coolant level sensor. Immediately the temp needle went to full hot and
the red light started flashing. Once again, this is with the coolant temp
sensor disconnected. Is this how it is supposed to behave?

Does anyone have any clues as to what is going on? My theory is that there
is something wrong in the instrument cluster. My guess would be (and only a
guess) that the low coolant level control unit might be malfunctioning
somehow. Might any of these components be serviceable, or do I just need to
get a new instrument cluster (if that is in fact where the problem is)?

Any and all help would be greatly appreciated.

Bruce

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