Heater valve potentiometer

[Cerberus90]

Does anyone have any clues/ideas on how best to modify/adapt the heater potentiometer from TVR-parts onto the heater control motor? The new pot is much larger than the old one and doesn't fit in the white nylon holder, also the hole for the shaft is much larger so the motor shaft won't turn the pot.

Already removed the white nylon holder, I'm going to try and hot glue the pot on, but I'm not 100% confident it'll hold it well enough.


Thanks

[David Beer]

Iam sure you can get the correct size from Farnel. Is it 100 k ?

[Cerberus90]

10k, three pin. I'll take a look and see.

• EDIT*

Nope, none that look correct, and the postage from Farnell is apparently £16, which makes the whole thing pointless,

Edited by Cerberus90 on Thursday 25th August 19:27

[dnb]

It is 100k, but it's a 15mm diameter potentiometer and this form factor appears to be obsolete.

I managed to make an adaptor so I could use a JM74R modified with a slot cut in to it from Maplin.

[Cerberus90]

Could have sworn the new one had 10k printed on the side, , nvm, it appears to work, just a natter of mounting it on the motor

Just have to see how the hot glue goes and then try and come up with something else if it doesn't work.

[Loubaruch]

Cerberus, what year is your car? It would seem that your original pot. is very different to mine ( 1996, 500),have you a pic?

The TVR Parts potentiometer fitted my valve OK with some modification see:

http://www.bertram-hill.com/heater-problems.html

[Cerberus90]

It is a 10k pot, got some pics of the old one showing 10k.

Got some pics showing the differences, can put them up later.

Got the pot mounted with hot glue, just trying to sort out the centre shaft, got two bits of zip tie wedged in at the moment which just about does it.


Oh and it's a P reg griff.


Comparison of old pot and new pot :


New pot sat ontop of the white plastic 'holder' :


Motor pivot shaft :

Edited by Cerberus90 on Friday 26th August 18:12

[dnb]

Truth be told it doesn't much matter what value the pot has, as long as it is linear and total resistance is large enough to stop excessive current consumption.

[Loubaruch]

The potentiometer on your "P" car is very different to that on my "N" 500. Perhaps been replaced at sometime or a change by TVR.

The TVR Parts replacement pot. is 15mm diameter as was my original and does fit into the plastic holder OK by bending the connection tabs.

The central hole on the TVR parts replacement is too big for the shaft, a bit more from the glue gun should sort that.

As the original 15mm 10K pots are now obsolete I have tried two similar types (from the states)the TVR Parts version is the nearest to the original but does require modifying.

[Cerberus90]

Suppose it's possible that it's been changed, wouldn't surprise me if that's how it left the factory and they'd run out of one sort and just chucked this type on.

The white pot holder is very different to the one on your site in that it's round rather than tear-drop shaped.
I'll try and get a look at the other motors and see what type they are.

The hot glue just didn't seem strong enough to hold the central shaft, don't really want to use something like chemical metal either as that's a bit too permanent and could lock the shaft to the motor plate if it runs down the shaft a bit too far, also wouldn't be very easy stuffing the stuff into the hole.

Spoke to an engineer the other day to see if he could make up some sort of shaft adapter to fit over the motor shaft and be the correct OD for the pot, but he said it was too small.

Have been told that RS / Farnell/ CPC might have some shaft sleeves/adapters, so I'm trawling through them at the moment,

Maybe a new motor from TVR would sort it as that should fit the potentiometer better?

Edited by Cerberus90 on Saturday 27th August 17:02