My heater control just reversed polarity!

[RichB]

Well I know someone is bound to say "they all do that" but personally I have never heard of this one before. Just went out to post some Xmas cards and being a nice day decided to take the long route After about 10-15 mins the car was still decidedly "fridgey" inside, fiddled with the blower etc. but no difference. Finally in desperation to thaw my toes I twiddled the heat setting knob and guess what? I turned it anti-clockwise, round to the green light, and all of a sudden the heater blew out loverly hot air! Now explain that one to me please? p.s. It's been normal for the first 3 1/2 years of it's life. Rich...

>>> Edited by RichB on Wednesday 18th December 13:04

[beano1197]

at least it wasn't the gearbox!!!

Mine (knobs - oo-er missus) have a mind of their own, hadn't thought about twiddling them the wrong way, yet.........

Thanks for the tip!

[simon.b]

Mine did exactly the same a couple of days ago.

For some time now if it’s been a cold night the motor has activated on it’s own just as the car starts to warm up by closing and then opening again, but then the other day complete reversal hot was cold. Yesterday and this morning all back to normal.

What causes this then ?

Cheers,

Simon.

[david beer]

I think its to do with lack of temp compensation in the control brain. Thats why in summer when you turn the heater off after a while it will not go completely cold. So you have to keep it off from start up.Well thats my theory.

[simpo one]

Has the knob slipped on the shaft a bit?

(clean minds only please)

[RichB]

I think its to do with lack of temp compensation in the control brain.

Or could it be significant expansion/contraction of the cable (or whatever is activated by the servo) that over centres the control rods?

Has the knob slipped on the shaft a bit?

No. The knob had to be rotated in the opposite direction i.e. hot was cold and cold was hot. Not just hot was where cold is and cold is further around the dial. Or at least I think that was the case!

[sideways500]

I was told (by a main dealer mechanic) that the heater control valve (from a mkI Golf) can "over centre". That is to say further turning in the cold direction will open the valve again. If the potentiometer is badly adjusted this might result in the controls working back to front. Maybe.

[RichB]

Well I just been out and all is back to normal again, quite warm from the cold setting and bloody hot from the hot position. It's nice to know TVRs can mend themselves isn't it? Rich...