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water tank depth guage - fixed that too!

Printed From: The Brick-yard
Category: T3 Section
Forum Name: T3 Westfalia forum
Forum Description: Forum to discuss VW T3 Westfalia models. If it's shit, it goes!
URL: http://www.brick-yard.co.uk/forum/forum_posts.asp?TID=13907
Printed Date: 23 Nov 17 at 07:22
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Topic: water tank depth guage - fixed that too!
Posted By: calvin
Subject: water tank depth guage - fixed that too!
Date 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 thin-nosed 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!


-------------
Ever tried eating a clown? They taste funny.
'89 2.1 Westy California darn sarf, Sussex.
+++ Still looking for good OSR big bumper corner section PLEASE! +++



Replies:
Posted By: paulm
Date Posted: 13 Mar 07 at 22:33
Hi Calvin,

Did you come across any source for replacement plastic tubes on your travels?

Mines got a wee hole in it, which lets the water in & corodes everything. Any suggestions for a waterproof glue as an alternative would be useful - I haven't found any food grade araldite so far!

Cheers,

Paul


Posted By: calvin
Date Posted: 14 Mar 07 at 01:43
kitchen / bathroom silicone sealant should be ok. As far as i know, that's inert.

-------------
Ever tried eating a clown? They taste funny.
'89 2.1 Westy California darn sarf, Sussex.
+++ Still looking for good OSR big bumper corner section PLEASE! +++


Posted By: cooky73
Date Posted: 14 Mar 07 at 14:52
I need a new magnet - any ideas on this?

-------------
2003 Westy California TDi


Posted By: cooky73
Date Posted: 19 Apr 07 at 10:40

i have fixed mine but still no magnet

can you show a larger pic of the floating magnet or describe what it is made of please Calvin?



-------------
2003 Westy California TDi


Posted By: Tim Hamnett
Date Posted: 19 Apr 07 at 11:06
Most sealants for kitchens/bathrooms etc contain things like fungicide and should not be used in contact with drinking water. Pottable water sealant or aquarium sealant is safe.



Posted By: pete23
Date Posted: 27 Apr 07 at 10:29

mine is broken too but the repair seems a bit technical for me- no soldering experience since burning my fingers at school-  any chance you would consider repairing it and how much would you charge for this service.

thanks pete



Posted By: badger
Date Posted: 14 Aug 07 at 20:59

Does anyone know what material the float is made out of (stainless/PVC??) plus rough dimensions if possible. Found a place that can supply magnetic floats but need to know some basic's to spec it first.

Edit: Sourced a supplier for a suitable float - http://www.deeter.co.uk/deeter/sc/categories/category/viewCategory.htm?operation=viewCategory - http://www.deeter.co.uk/deeter/sc/categories/category/viewCa tegory.htm?operation=viewCategory  DEF 50-4  float, it's a snug fit on the float tube, had to remove a small amount of excess adhesive from inside the bore of the float before fitting.

Still had problems with the lower reed switch - water ingress had damaged it, replacement reed obtained from here

http://www.rapidonline.com/productinfo.aspx?kw=reed%20switches&tier1=Electronic+Components&tier2=Sensors&tier3=Proximity+Switches&tier4=Reed+switches&moduleno=30247 - http://www.rapidonline.com/productinfo.aspx?kw=reed%20switch es&tier1=Electronic+Components&tier2=Sensors&tie r3=Proximity+Switches&tier4=Reed+switches&moduleno=3 0247

order code 60-0524 for the lower reed, probably 60-0522 would be suitable for the upper reed.

Important lesson learned when refitting - it's essential that the tube is completely dry inside befor re-inserting the reed switch assembly, any moisture seems to affect operation of the switches (probably due to a change in resistance across the copper strip due to the moisture?)

3 working LED's finally



-------------
1989 Westy California 1.9 AAZ



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