How does this unit normally fail: Does the solenoid wiring go open circuit / burn out - or does the valve get gunged up and jam? Can it be dismantled for repair?
How are variations in temperature acheived? Surely a solenoid device is either on or off.
Many thanks to any one who responds.
The natural state of the valve is open so coolant flows through the heater. (hot)
The temperature knob operates a simple thermostat type circuit which cycles the solonoid on/off/on/off. For example 30seconds on, 30 off might give 50% heat output. It doesnt work with these timings, but you get the idea.
They normally fail open so you roast, but can equally fail shut too. They are non-dismantleable.
Tim..
Conor wrote on Thu, 19 Jan 2006 23:26:21 -0000:
FFS. You clearly went to some deliberate effort to snip
"Surely a solenoid device is either on or off."
Which, had you left it in, shows your answer to be the useless truism it is.
Sunday Driver wrote on 19 Jan 2006
15:05:22 -0800:I believe that the solenoid is pulsed on and off to vary the amount of water which reaches the heater matrix.
of all the ones i've changed the supply wiring is usually ok, one the end of the solenoid there's a plastic guide thing which stops the flow of coolant to the heater matrix. i think they just seize up its a sealed unit and cannot be dismantled ,ive never tryed though -may cause a coolant leak anyway.
yes a solenoid is off or on, by putting your hand on it you might feel it pulse, the timing intervals of these pulses is determined by a variable resistor inside the car (the temparature dial)
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