Heater water valve motor fault

[Ozstyle]

Hi,

my heater valve motor has lost the plot and continues to run all the time, regardless where the control knob is turned to. I've checked the the that the knob is firmly attached and turning the resistor pot on the heater control panel which it is. All other heater controls work as they should.
I can only assume iether the resistor pot or the electronic control unit behind the dash is at fault. Has any one else had this problem who can give me a clue as what I need to look at to fix. (94 Griffith 500)

thanks

oz

[BliarOut]

Check the ribbon cable that goes from the lower switch panel to the "environmental control unit" Sometimes you can get to it through the radio slot or you might need to lift the centre console. Took me bloody ages to find that one as a cause.

[David Beer]

If one of the three wires has come off the variable resistor, the motor will spin. They are too heavy duty wires for the small tabs and break. You will have to get upside down to see it on the motor.

[BliarOut]

David Beer said:

If one of the three wires has come off the variable resistor, the motor will spin. They are too heavy duty wires for the small tabs and break. You will have to get upside down to see it on the motor.

That whole assembly would have been potted in a production car

[2Munkys]

This gubbins? If the crank with its limit switch trigger screw (for want of a better term) has detatched from the output shaft, would the motor not continue to operate?

[BliarOut]

The heater control valve is a 360 rotor. It just spins and spins and spins and spins and spins and spins a bit bloody more.

[Ozstyle]

Thanks for the input,

I removed carpet around the valve motor, set the control knob to closed and switched on the ignition and watched the motor turn the valve through 360 degrees a few times (there are no limit switches on this motor unlike the others in the heater system). I could not see any problem with the wiring at the motor. I grabbed the valve arm to try and hold back the motor but but could not, then a few seconds later the motor stopped the valve in the closed position. Everything is back to normal (for now), I can control the heater valve as designed.

Still can't work out what the problem could have been, can anyone explain how this motor is actually controlled to stop at the open and closed position without limit switches.

thanks

Oz

[Loubaruch]

Simplified explanation here:

www.bertram-hill.com

Edited by Loubaruch on Thursday 26th November 00:04

Edited by Loubaruch on Thursday 26th November 00:04

[Marty V8]

If its the heater control you are referring to rather than the recirculation motor and flap valve, then yes, it just spins and spins and then spins some more. I took mine out to see if it was faulty and when comparing it to a new one - they are Polo items I believe - the stop limits had been filed off. This is presumably so that the motor doesnt burn out against a stop as there are no limit switches fitted, even though there are to the other heater controls (recirculation and position of air output).

Turning the control just makes it go hot, cold, hot, cold, hot - always ending up hot of course.

I tested mine once it was off by blowing through it whilst turning the valve by hand. The valve only just shut off through a very small rotational angle and this would be impossible to hit by trial and error whilst driving.

I ditched the original and fitted the new Polo one but havent wired it up as Ive left the limit stops on it. Temperature control is now manually controlled and is the passengers duty by reaching under the dash, although its set to cold for summer. I may at some point connect it up to either a choke cable type control, or try to fit it back together and use limit switches tied into the motor somehow.

Edited by Marty V8 on Friday 18th June 23:26

[Ozstyle]

Hi,
thanks for the link, I have a better understanding now.

I replaced the water valve a year ago (VW item if I remember right). The valve needs to turn through 90 degrees to go from shut to fully open. I found when setting it up that the TVR electrics only rotate the valve through about 60 degrees, so it is never possible to get full water flow to the heater matrix. I think the non electrical control like the Chimaera is a better set up.

Oz

[Loubaruch]

Yes, not one of TVR's finest moments. Probably better to set the switch to fully turn off as there is usually too much heat in the cockpit especially where you are! You will probably find that even when fully closed a fair amount of heat still trickles through the heater. Search the Griffith threads, there should be plenty of info on various ways of tackling the problem.

[Ozstyle]

Old thread but I thought I would close it out just incase anyone goes looking for help on this subject.

My heater water valve motor came good for a while, but recently sarted playing up again, continually running, stopping starting, hunting from position to position but sometimes behaved itself. I pulled the motor and valve out, checked all the wiring to the motor and 10K control pot, all good no loose wires, checked the 10K pot for resistance and dead spots, all good. Whilst head in footwell feet on head rest checking the motor I tidied up the wiring from the valve motor where runs behind the glove box the motor started running, everytime I moved the wiring I could make the motor stop and start - obviously indicated a bad connection in the wiring from the heater ECU to the valve motor. I decided to remove the wiring from heater ECU to the valve motor to check for continuity, accessed the heater ECU behind dash, only had to remove radio and left heater vent to get to it. On removing the valve motor ECU plug (middle plug of 3) one of the 5 wires fell away from the plug (it was the blue wire that connects to the 10K pot), looked like it had broken off at the connector crimp in the plug. Luckily it's possible to push out the female connector from the plug, I soldered the wire to the connector and reinserted into the plug, connected everything up. So far so good valve motor is now behaving itself.

Ozstyle