HCV continually rotating?

[BliarOut]

What tells the HCV when it's where it should be? Mine's just twirling round and round like a twirly thing once the ignition is on, no matter where the switch is.

Still, at least it isn't seized

[Simpo Two]

Heater
Control
V... err

Wot?

[BliarOut]

Yup, that's the spinny thing... The heater Control Valve. I thought everyone who owned a Griff knew everything about them

Just need to stop mine doing a very passable impression of a roundabout!

[Simpo Two]

Ah, the Knob

There's a very small grubscrew at the base. Turn the knob to the position you desire and tighten it up.

[V8 GRF]

Simpo Two said:

Ah, the Knob

There's a very small grubscrew at the base. Turn the knob to the position you desire and tighten it up.

No not the knob, I think he's talking about the potentiometer in the footwell.
There was a thread about this recently IIRC.

Search for heater potentiometer.

[BliarOut]

Yup, it's the pot I'm on about... I think it's lost it's ability to know where it is or it's continually being told to rotate. What actually tells it where it is?

[Ballistic Banana]

Hi Rob,

Dnb gave me this for the Alt Parts list

Heater Pots. Farnell's Part no. 919573 and cost £4 each.

HTH

BB

[BliarOut]

Cheers Simon, top sleuthing

Don't suppose anyone has a part number for the motor?

I noticed in the wiring diagram that there appear to be a couple of diodes (03) and (04) between the temperature control motor and the temperature switch. Does anyone know if they're external and where they if so? With my limited electronic knowledge I seem to think a failed diode could cause the problem by creating an imbalanced circuit?

Edited by BliarOut on Saturday 3rd November 08:15

[David Beer]

I bet its a lead off the variable resistor on the valve. The wire is "huge" compared to the circuit, shame tvr didnt practice this with the cooling fans,starter solenoid, headlights,leccy windows etc.

[Loubaruch]

Check that the potentiometer is actually still on the end of the HCV motor. Mine seems only to be a push fit and while recarpeting I dislodged it and had the same symptoms - continuously driven HCV motor.

Basically the Heater controls on the 500 models are simple servo's:

Comprising a heater control potentiometer (pot) - on the heater panel, a driving motor to close the valve etc. and a reference potentiometer connected physically to the motor. Some electronics connects the three items. When the contol is moved the motor drives the motor pot. until a null is reached. If you think of the motor pot as tracking the movement of the control pot you wont be far off.

So if the motor pot has somehow fallen off the motor, or a wire to it has disconnected or the pot itself is open circuit then the null point will never be reached and the motor runs continuously. It could of course be a fault in the electronics ( in the heater module) but generally they seem quite reliable. Best of luck
Paul

[red griff roger]

Simpo Two said:

Ah, the Knob

I think The Knob is just there to occupy you in traffic jams. You twiddle it round to see if there is a difference to anything, but there isn't. But it keeps you busy

[Argent]

You can get the complete assembly from TVR Carparts.

A.

[BliarOut]

Cheers chaps It was the crappy soldering in the end. Must have loosened itself a bit when I replaced the HCV in summer.

All sorted (for) now.