heater valves or aux pump

[Paul in NZ]

I often drive the 535 with the radio off.Sitting at the traffic lights the other day i could hear a light thumping sound aprrox two seconds apart.Stopped in the garage and turned car off,then turned key back to pos I and opened bonnet.Quickly traced sound to the heater vavle area.
The top of the heater valves were hot and could feel and hear them opening and closing???Or is it the pump???
Any thoughts gentlemen???

[BigKriss]

i don't know Paul. Is your heater still working?

[Paul in NZ]

heater still works sometimes tho has a mind of its own and pumps heat out of drivers side dash top triangular vent only when rest of the system is at selected temp
Oh IHKA by the way
Didnt one of you aussies replace heater valves and aux pump assembly?why?

[Morgenster]

The aux pump is just water pump to get the coolant through the heatervalves. If one of them is stuck open (which is usually the default position if a valve fails) you'd always have heat on either the passenger or drivers side.
If such is not the case and the valves open and close randomly then it's probably electrical and I'd try to see if the valves are getting constant power (12V for closed and 0V for open).
The entire pump and valve assembly aren't hard to replace but new parts can be a little costly for its function. My valves were replaced at 50 euros by my mechanic. He used a functioning used one.

[pundit]

heater still works sometimes tho has a mind of its own and pumps heat out of drivers side dash top triangular vent only when rest of the system is at selected temp
Oh IHKA by the way
Didnt one of you aussies replace heater valves and aux pump assembly?why?

The heater valves constantly cycle open & closed to maintain the temp... hence the source of some of the E34's weird noises.
Over time the internal seals of the heater valve assembly (that prevent water from entering the solenoids) fail and the resultant build up of corrosion and sludge causes the valves to stick. This is usually the cause of intermittant heater operation. Mine tended to stick in the 'on' position on the drivers side. Tapping the valve assembly temporarily cured the problem.

Remember the valves are in the normally open position (heat on) when no power is applied. Powering the solenoids closes the valves (heat off).

I would first check to ensure your solenoids are powered correctly.
The aux pump can be easily checked by powering it directly. This is a fairly low volume pump and really only offers benefit at idle.

Other possible faults are incorrectly functioning vent flaps, but I'd begin with the heater valves first.

[Paul in NZ]

multi meter on voltage across heater valve wires or 1 wire to ground will show a 0 reading at coldest and 12v at hottest?

[Morgenster]

multi meter on voltage across heater valve wires or 1 wire to ground will show a 0 reading at coldest and 12v at hottest?

I think it's the other way around.

[pundit]

multi meter on voltage across heater valve wires or 1 wire to ground will show a 0 reading at coldest and 12v at hottest?

As already suggested, the other way around.
The application of 12 volts keeps the valves closed (heater off).
Removing the power opens the valves (heater on)
The heater valves are designed to remain in the open position if power is lost.
This is to avoid freezing ones 'proverbials' off in a Northern European winter should power to the heater valve circuit be lost... although the valves can still stick closed once the internal seals fail.