Simple wiring for coolant level idiot light?

[veloandy]

Hey Everyone,

I thought I'd post this to hit up the collective Samba wisdom once again...

I have an originally-air-cooled 1981 Westy. I swapped in a Subaru engine. I have the stock air-cooled gauges, plus an aftermarket electric water temperature gauge. I recently got The Tank from Rocky Mountain Westy, and I'd like to hook up the coolant level sensor in The Tank to a new idiot light on the dashboard. The coolant level sensor reads about 800K Ohms when immersed in coolant and infinite when dry.

How do I wire up the idiot light to come on if the coolant runs dry? A normally-closed relay won't do it -- the 800K Ohms is too much resistance to activate it.

I know the stock WBX cluster uses a coolant level warning control unit to figure out when to light up the LED to indicate a low coolant level.

It seems like my options to get a low coolant level indicator light are:
1. Get the gauge cluster and coolant level warning control unit from a later van and wire them up.
2. Bust out an Arduino and hack up my own coolant level warning control unit to light up a light only when there's infinite resistance at the sensor.
3. Give up and just not have a low coolant indicator light.

Am I missing a simple way to wire a light to come on when the coolant runs dry?

Thanks!

[insyncro]

They changed the sensor used a couple of times now, not sure, ask Mike he should know.

[jmranger]

The arduino isn't a bad idea, but you can do much simpler with plain transistors and resistors.

A voltage divider with one of the resistors being the coolant sensor, an NPN transistor as a logic inverter circuit and a few more resistors for polarisation and current limiting for the LED should do the trick. Roughly $1 in parts.

If you want to simulate if, have a look at the free LTSpice simulator.

[markd89]

Google LM1830. I used one of these to build a low coolant circuit for my bus. It triggers a relay which runs a warning light and a very loud warning.

There are other integrated circuits which also make such a setup pretty easy.

Good luck!
Mark
_________________
78 TDI Sunroof Bus
Los Angeles

[squeegee_boy]

I put in one of these:

http://www.coolantalarm.co.uk/shop/index.php?_a=viewProd&productId=3

...since my digital gauge cluster doesn't have a coolant indicator circuit.

It wasn't exactly cheap, but after several failed attempts to build a reliable one using voltage dividers and other things, it was nice to be plug and play.

I didn't know about the LM1830 though... that looks cool.

Robyn
_________________
1984 FrankenSyncro Westy. EJ25 RMW kit
1971 Super Beetle with an EJ22. Oh yes. Daily driver

[danfromsyr]

you need the relay for the float contacts (don't actually float)

VW relay #42 or #43 part number 191-919-376A
http://www.van-cafe.com/home/van/page_1187

some reading from the vanagon 80 90 club
http://forum.club8090.co.uk/viewtopic.php?p=7630031&sid=6e5244451222b4194600757bc62a1208


http://wiki.club8090.co.uk/index.php/Coolant_and_Heating_flashing_red_light_on_dash
_________________

[danfromsyr]

_________________

[Vanagon Nut]

I'd think the coolant low module (relay) could be found in a wrecked Vanagon.
Would suggest '86+ parts for that.

The Diesel Vanagon coolant gauge would also work. I wonder if a gauge from a
Mk2 would work?

Neil.
_________________
1981 Westy DIY 15º ABA

1988 West DIY 50º ABA

VE7TBN

[crazyvwvanman]

Various other VWs from around 85-91 used the same setup and the same module. Many had no coolant level sensor and warning system but the ones that did mostly shared the sames stuff as the Vanagon of the same year.

Mark

[Vanagon Nut]

^^ Useful to know Mark.

At the OP: here's the part I used. It's NOT the early style module that pins the coolant temp needle and causes red light to blink in a coolant low event; it just causes the red light to blink.

Neil.

_________________
1981 Westy DIY 15º ABA

1988 West DIY 50º ABA

VE7TBN