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MG MGB Technical - Heater control knob stuck on!

Hi all,

I only bought my car - '66 BGT - in February, it was still cold and snowy. Heater worked great on the run back home and subsequently.

Now the weather has turned milder, so I went to turn the heater down/off, as the footwell is too warm. Both the knobs are stuck in place, if I try to turn them I fear they'd snap off.

My question is: is this a well-known issue, with a well-known solution? I thought I'd ask on here before I start pulling things apart...

It's a Mk1 in decent nick.

I have scoured the archive but couldn't find anything about this.

Many thanks for any thoughts.

Piers
Piers Colver

Could be seized cables or seized controls.

The easy thing to check first is if the tap on the cylinder head is free. Disconnect the cable and try moving it manually. Also try the temp control knob while you have the cable disconnected.

You have flaps over the heater vents in the footwells which can be closed, just like your Sprite did.
Dave O'Neill2

If the cables or valve/flap are seized the knobs should still turn as there is lost motion in the gearing at the dash control. Likewise you should be open and close the valve on the cylinder head a bit even if the cable inner doesn't move.

So is the knob seized, or just turns a bit but doesn't alter the valve etc.? If it moves a bit can you move the valve a bit or not?
P Hunt

it's common, lack of use and lack of a bit of occasional lube service

like the horn, wipers, lights, heater blower, and in fact everything on the car it's best to test them to keep them from seizing up and to make sure they're working before you really need them, easy to do if you use the car regularly

it's also common that no matter how you set valve and cable that it either wont fully shut or fully open, so if you get too warm when it's set to full then set it to fully close and visa-versa if someone in the car is never warm enough

there's a John Twist video on YouTube about this

also the heater valve, like the rest of the cooling system if not keep clean, can get get clogged up inside so restricting the amount of hot water getting to the heater matrix

aint I just full of joy :)
Nigel Atkins

Morning all,

Thank you for the various comments.

The knobs turn a little, a few degrees, but are very tight - it is more as though they are twisting something rather than turning it mechanically - and when released they return to their original position (fully on). The heater is currently on and working - when the engine is up to temperature, hot air floods both footwells evenly.

I will look for the valve and flaps etc and have a look at all that. The car was bought from an older gentleman who only took it out on his own, so thinks that he used work well, other things will need me to start using them then they should be fine - I think he was happy with the heater permanently on, so it has not been operated in years.

Similarly, I discovered last night that the passenger seat runner is seized, so the seat will not slide forwards - I'm going to try soaking it in WD40 but if anyone has any other tricks feel free to share! The lever operated the mechanism fine, it is just that the runners will not slide the seat forwards. Sigh.

Anyway, I am rambling - thank you very much for the responses, I'll investigate the heater.

And Nigel - all responses welcome, joyous or otherwise!

Piers

Piers Colver

Seat runners - I would take the seat out. It is only four bolts after all and then clean it all up with a wire brush. A good coating of grease where the runners slide on each other and bolt it back together.

Mike
Mike Standring

You can get at the dash mechanism it-situ to some extent. A cog on the end of the knob shaft engages with a quadrant that carries the cable inner, as shown here. It may be the quadrant seized on the control, or the inner seized in the outer, which were steel in steel originally. You should be able to tell which by felling behind the dash as you turn the knob.

As far as seats go if the wooden packing strips under the runners have rotted away the bottom runner may well have buckled downwards. They should sit on four spacers that go through the carpet or mat and packing strips, being bolted down without the spacers can buckle the runners upwards.

P Hunt

Mike and, er, P those are fantastic responses, thank you very much. Good to have a couple of projects for the weekend!

I see that new runners are £15 or so for one seat so I'll keep that as a backup plan should I struggle too much.

Mike - I'm ashamed to admit that it never occurred to me that the reverse of the mechanism might be visible behind the dash. D'oh!

Thank you for the responses, both of you.

Piers
Piers Colver

Piers,

for the runners and heater control mechs instead of using ordinary WD40 to release them use a good penetrating/releasing fluid like PlusGas

I've still got a couple of the seat spacer circles or I should say they look like they are to my memory, good enough to give you an idea what they look like, so if you need a photo of them

a list of additional lubes for you home/garage
• light oil (like 3-in-One)
• (thin) spray lubricant
• penetrating/releasing fluid like PlusGas (ordinary WD40 is not that good)
• silicone lubricant (for rubber, nylon, etc.)
• electric contact grease
• (electrical contact cleaner)
• anti-seize assembly compound (like copper grease)
• all-purpose grease (and gun)
• cheap artist brushes – to apply copper grease, all-purpose grease, etc.
Nigel Atkins

This thread was discussed between 30/04/2013 and 02/05/2013

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