Westy water tank level sensor repair

Top fella, good info and pics there, ultra-useful

Hi James

I have it as a word doc, so could e-mail it to you if you want??

Just PM me your e-mail and I'll send it.

Cheers
G

Hi
Here's the write up done by Lagerhead, sorry no photo's but I do have them in the word doc so can e-mail that it anyone needs them.


Posts: 913 Topic: water tank depth guage - fixed that too!
Posted: 13 Mar 07 at 00:12
One of the apparently common failings of the westfalia kit is the depth guage inside
the onboard water tank. I made it a mission to replace mine until I found that they
could be repaired. Here's what I did
A post from Lagerhead on 80-90 was really helpful as it led me to understand how
these work and consequently how the inners must be constructed to enable it to be
manufactured consistently.
As he says, they work by the float (which contains a magnet) opening and closing 2
reed switches to effect a pre-determined amount of resistance (through the two inline
resistors). The amount of resistance makes 1 of the 3 LED's in the control panel light
up. Simply really!
It appears to me that these sender units quite commonly fail for 2 main reasons:
a. the plastic rod leaks and takes on water which causes corrosion and deformation of
the copper strip.
b. the magnetic reed switches break (probably because the rods get bent or they are
made to bend due to water getting in and so causing the double sided copper clad
"rod" to bend)
NOTE- these rods are actually VERY fragile, so NEVER try to straighten a bent
one - this is what breaks the glass reed switches!
So, to repair them (mine was pretty well trashed, so i reckon that they can always be
fixed as long as all the main component parts are still present):
1. unplug the 2 wires to the depth rod (black and green) from the clear multi-plug
connector block which is found in the rearmost locker under the westy table
(you will need to remove one small screw to swing a metal plate back to
reveal the lid to the water tank).
2. Remove tank cap/lid and carefully withdraw complete with rod.
3. You may have to carefully "break" the glued connection of the rod and the
grey mounting cap, mine slipped out easily but they were originally glued.
4. Snip the connections of the two wires where they enter the top of the plastic
rod to free it.
5. using a sharp knife, break the seal of the glued grey plastic cap at the bottom
of the rod and remove the plug (this is where they seem to leak from)
6. push the inner rod through from the top (where the wires were) or use thinnosed
pliers to pull it from the bottom - it should only be glued / sealed
slightly at the top if at all.
7. Once you have all the pieces, it should be obvious that the tiny magnetic reed
switches are broken, mine were filled with water and like tiny spirit levels
with bubbles in too!
(all the bits..)
(
upper switch..)
(lower switch..)
8. Obtain new reed switches and desolder the old ones to replace with the new,
ensuring the rod itself is kept absolutely flat and straight - DONT TRY TO
BEND IT AFTER SOLDERING! or you will break the reed switches again!
(The switches can be found at Maplin, RS and Farnell, but look carefully at
the description, these are miniature switches and there's no room for anything
bigger! The top one is a SPST type - single pole, normally open (ie open
circuit until a magnet goes over it), the lower one I found much more tricky to
locate a supplier for as it's a DPST - double pole - this one has to be soldered
in to be closed and the "open" leg cut off short and not touching or soldered to
anything.) You can easily test the switches with a multimeter and a magnet to
check connections etc.
9. Ensure there are no short circuits, solder lumps or bumps, or anything more
than about 2-3mm above the surface of the rod, as if there is, it may not work,
or may not go back into the sleeve.
10. Depending on how easily your rod will feed back into the plastic sleeve, you
may need to go from the top or bottom - if you cleaned all the glue out, it
should make no difference. However, if you have to push it up from the
bottom, then carefully push the copper rod complete back up into the plastic
tube, pushing it through about 1/2" clear so you can resolder the wires to both
sides at the top.
OR.. solder the wires on first (doesnt matter which goes to which side, but
make sure no solder short circuits the two sides!) and push the rod back into
the tube from the top.
11. push the copper rod back in flush, seal with silicon or similar to prevent
moisture getting in, replace the bottom plug and glue it / seal it.
12. I used bathroom sealant to seal the lower plug and also the seal between the
rod and the grey plastic top that is screwed to the tank cap- whatever you use,
remember that's your drinking water in there!
Hey presto - you should have working LEDs again; stand back an admire -
oooooooooh, fairy lights! (the top switch on the display should show you battery and
water levels)
If you need the reed switches and cant get any, I have some (only a few of the double
pole ones tho) and can supply one for each of the top and bottom for 10 inc postage.
I might even consider repairing these for others, it takes about an hour once you've
got all the bits, or 3 weeks if you learned on the way and had to track down the parts
like i did!
Hope this helps!

I'm here!!!

Top post sbbfuc.

I thought my sensor was faulty following stripping and refitting the van, it now always reads full regardless of water level. Surprisingly I took the sensor out and checked it with a multi meter and it's fine?

Looking through the Bentley manual it gave the steps to check the panel but unfortunately for an older model. I struggled to follow the instructions and eventually gave up.

Can you offer any advice to check the display panel or maybe an alternative reason for the fault?

It particularly pisses me off cos it was fine until I stripped and rebuilt the van.

Any help is appreciated

Cheers

Zeb


Edited by Zeb - 08 Jan 10 at 20:39

Hi Yes I'm pretty sure it isn't the sensor but I'll check again. I had three readings from it when sliding the magnet and as usual I probably did it half a dozen times to be sure, is there a range for each reading I should be looking for?

The reading from empty to full is very different but I did not record them, it leads me to think there is either a wiring problem or that part of the panel is buggered. If there was an easy way to check the panel it would be very useful as it is so simple to remove it.

I'll record the readings when I get the chance to check it again and compare to what you show in your post.

Cheers

Zeb

Time to go and search, I must have some electrical widget with resistors somewhere I don't need !

Thanks

Hi sbbfuk

The resistors arrived today, thanks very much you have saved me a load of hassle looking for a fault elsewhere in the system. I tried them out and got the correct panel readings instantly.

The level of resistance I was getting when I originally checked the sensor was too low to be correct. This gave me the confidence to dismantle the sensor and have a better look. After scratching my head for a while I discovered the top reed switch connection was burnt (under X10 magnification) it is not disconnecting properly and gives the false reading of full regardless of what the lower reed switch is doing. I can actually hear the lower switch click as the magnet passes over it so it seems to be fine and the contacts also look clean.

So I think all that needs to be done is replacement of the top reed switch.

Looking at the picture in your post I checked RS for the part numbers, I am now confused as both "394-428" and "229-3692" are listed as Single Pole reed switches, which one do I need for the top switch?

Thanks again for your help

Zeb


Edited by Zeb - 18 Jan 10 at 23:32

Hi sbbfuk

I owe you one already for sending the resistors !

Both part numbers are available from RS but I am not sure which one I need. On the picture in your earlier post you show the packets they came in so I checked the numbers and don't know which to order as they both seem to be single pole switches but a slightly different diameter. I think the picture on their site is a generic one so was no help.

If you can confirm which one I need to order for the upper switch I would be grateful, they both seem to be available and will only cost a couple of pounds. As they are reasonably priced it would be useful if you have a record of the part numbers for both and I will order them just in case I manage to break one when putting the sensor back together.

Cheers

Zeb

Thanks, they were the numbers I took from your photo's, I was not sure though as when I looked them up they are both listed as single pole, am I mistaken or is their listing wrong ?

Cheers

Zeb