Date: Tue, 13 Mar 2001 16:09:23 -0800
Reply-To: TinkerMan <tinkerman007@YAHOO.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: TinkerMan <tinkerman007@YAHOO.COM>
Subject: Re: Water Level Indicator Red Blinking Light
In-Reply-To: <001401c0a99c$17395700$a1c0c2d1@i8p2q9>
Content-Type: text/plain; charset=us-ascii
--- George Averill <averill@LDL.NET> wrote:
> I need some ideas for replacing the temperature gage
> that contains the red blinking light that indicates
> low water in the water reservoir. This has been an
> ongoing problem for several years. Now I am working
> on it again.
Mine has never failed. Only the sensor in the pressure
tank. More than once. One time it broke completely
when I tried to retighten it to solve a blinking water
level indicator problem. I was stranded but managed to
get away by improvising.
Another time it cracked and let water seep up to the
connector without me knowing it. This caused me to
lose a motor because it disabled the water level
sensor (the external wet sensor leads signaled as if
there was water even when there wasn't). When I had a
water leak from the oil cooler one night, the sensor
didn't detect I had no water and let the motor burn up
after a 15 minute drive. Big price to pay for a $10
part...
Also, the coolant pressure tank tends to crack too and
cause coolant loss.
For the benefit of the list members, here is a short
description of how the system works: Basically, the
coolant level/temperature system is quite complex. The
coolant temperature meter actually includes
electronics within it, because the same input line is
used to indicate temperature as well as signal the
coolant loss lamp.
The meter is activated by the current passing through
the temp sensor (a temp dependent variable resistor).
It has a slowed down response (averages) by using a
heater coil to heat a bi-metal strip which in turn
delects the meter pointer. Compared to the coolant
indicator lamp this is still simple...
The coolant level warning lamp is driven by the
coolant loss detector (a relay-looking box on the
relay panel that actually contains electronics, even
IC's). This detector is driven by the coolant level
detector in the coolant evapration (pressure) tank.
To complicate matters even more, the two signals are
multiplexed (shared) on the single input to the meter
by using pulse modulation...
Those Germans sure know how to complicate things...:-)
I found this out while trying to debug that damn
circuit after I lost the motor. Since then I have
added an external warning system (audible and
visual)for coolant temperature as well as head temp.
It's simply too easy to miss that warning lamp when
the sun shines in from the front...:-(
> In the past, I have replaced the gage with a used
> one that worked several months then quit. Then I
> replaced the gage with one from VW which lasted
> about six months.
Like others said, I agree the gauge shouldn't go bad
so often (if at all) unless you have another problem
(maybe the temp sensor gets shorted out and drives a
high current through the meter which might burn it.
> My questions are:
> 1. What sources are there for replacement gages?
Junk yards or mailorder. But are you sure they're bad?
> (Does anyone stock them besides the dealer?)
Maybe mail order outfits present on this list (Bus
depot, Vana-gain, etc.).
> 2. Has anyone built a separate water level gage to
> bypass the one that came with the vehicle?
Yep. A complex electronic circuit, but NOT INSTEAD,
but rather in parallel with the OEM system, as a
backup and enhancement.
I've also seen somewhere someone simply glue thermo
switches at various areas in the motor to sense hot
spots. Those switches connect to a buzzer in the
dashboard. GREAT idea and simple to implement.
> 3. Any ideas why the gages keep going bad?
Not sure they're bad at all. Check if they're open
circuited or not. You should measure a few tens of
ohms between the terminals (don't remember exact
numbers). Then apply a small current and increase it
until you see the meter deflects. Checking the coolant
LED is more complex, but it should blink for a short
while after power is applied and then turn off. This
is best done inside the van.
> Thanks in advance. If you send a reply to this
> message, please send it directly to me by e-mail so
> your reply won't get lost in all of the many
> messages on the site. I have a hard time reading
> all of them.
We all do. That's what email filters are for...:-)
In any case, I'm CC:'ing you too.
=====
Cheers,
TinkerMan
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