A slow leak at a radiator hose was the cause of loss of coolant  when I was
driving yesterday but there was no indication of low coolant until the
light flashed when the engine overheated.  :-(
 
Can  anyone help me to solve the problem with the low coolant level alarm?
 
I took off the expansion tank and checked the level switch.  It read around
800 K to 2 Megohms when dry and about 400K ohms when immersed in dilute
coolant, I assume that  the controller senses the resistance and thus
signals  a low level situation when the resistance increases (?).

Looking at the circuits in Bentley, I checked the switch wire continuity -
one to earth and the other to the relay - all OK.  There was 12 v on
terminal 5/15 of the control unit and no voltage on the other terminals. 
Does anyone know what the readings should be and is it possible to check
the control unit?

The warning light flashes for a few seconds on ignition switch on and on
overheating so it looks as if it's onlly the low level alarm that's wrong.

Also can anyone tell me where the engine bleeder valve is?  The photo in
Bentley is too dark to decipher.

Looking forward to some guidance TIA

Jack Newton
Sydney  Australia
'89 Transporter