Date: Sun, 18 Mar 2001 18:21:42 -0500
Reply-To: George Averill <averill@LDL.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: George Averill <averill@LDL.NET>
Subject: Re: Water Level Indicator Red Blinking Light
Content-Type: text/plain; charset="iso-8859-1"
Thanks to everyone who has responded to this message. By the way, I think I
have finally learned to spell "gauge". Sometimes it doesn't help to check
the VW spelling when you aren't sure. The page in the Bentley manual that
shows the schematic diagrams spells it "gage", but the header page that
lists the parts has it spelled correctly. The fuel "gauge" is also
misspelled on the schematic. Oh, well. Spelling definitely isn't my strong
point!
Here is where I stand. The red light has suddenly decided to come back on
and stay on when the ignition is turned on. It is supposed to come on and
blink, then go off. I assume this is a check of the components.
I have a new coolant low-level-warning switch (the two probes that protrude
into the water). They were installed this past summer when the plastic tank
started leaking. I have removed the two female connectors that attach the
wires to the coolant low-level-warning switch, cleaned them and tightened
them. No corrosion was evident. They may have been a little loose. (Note:
The red light came on before I did this.)
I replaced the coolant low level-warning control unit and the combined
coolant temperature gauge/coolant over-temperature warning light about a
year ago. Don't think the low level-warning control unit was bad. I think
the problem was a bad combined coolant temperature gauge/coolant
over-temperature warning light. Any way, things worked great for a couple
of months. Then the red light came on and wouldn't go off. Then it went
off and never came back on until this week.
Questions:
1. Do you have any suggestions for checking out just the coolant low
level-warning control unit? If I can determine if the old one I took out is
OK, then I can swap out the one that is currently in the plug. Both may be
bad. It's a real pain to get to the coolant low level-warning control unit
that is mounted on the side beneath the dash. What signal does it put out
that gets multiplexed with the variable resistance/current circuit of the
coolant temperature sending unit? I may be able to put it on a
oscilloscope. Have you ever done this?
2. Can you send me the schematic for the parallel circuit you designed that
had audible and visual indication of the loss of coolant?
3. Do you have any idea how much the voltage (10v regulated) to the gauge
can vary? I was also having problems with the 10v voltage regulator blowing
out. I finally built an external 10v supply to replace the single chip that
was in the circuit. I later learned that there was a modification to the
circuit that added a diode in one lead of the regulator chip. My regulator
incorporates a variable resistor to change the voltage and may not be
exactly 10v. It is very close, and the temperature meter reads mid scale
where it should after the engine has warmed up.
4. Will the red light come on, blink, then go off if the coolant low
level-warning control unit is removed from the circuit?
What someone really needs to do is to connect the components on a workbench
and take readings for comparison to one that is connected in a vehicle.
Please respond directly to my e-mail. Thanks again in advance.
George
P.S. Next week I will finish working on the broken sliding door handle
problem. Thanks to everyone who responded. I don't seem to have time for
more than one problem at a time!
----- Original Message -----
From: "TinkerMan" <tinkerman007@yahoo.com>
To: "George Averill" <averill@LDL.NET>
Cc: <vanagon@GERRY.VANAGON.COM>
Sent: Tuesday, March 13, 2001 7:09 PM
Subject: Re: Water Level Indicator Red Blinking Light
> --- 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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