Morris Minor Owners Club

I get air out of the 4 holes (screen & feet) & out of the front rectangle when on demist but that's because there is no sponge left on the plate that directs the air when you move the toggle.

I have a mini heater in my shed & that doesn't chuck any out the rectangle at the front when on demist (from memory..)

57,

I suggest that the vent problems is caused by perished foam inside the heater between the matrix and the housing.

I took Hebe's heating system apart yesterday; Replaced the send tap (that was the intial reason for me doing the renovations), replaced the two pipes (which had perished so much I could pull them apart with my bare hands! ! and de-fuzzed the heater.

Removing the heater is pretty straight forward. Just remember to take the wires off first (there are two lucar connectors to remove and one lead from the wiper switch (Presumably where it gets it's earth from). you should see some foam stuck on the matrix around the edges (to help prevent the air from going around the matrix rather than through it). On Hebe most of this either fell away or had disintegrated inside.

It's that same foam that is on the leading edge of the air "switch", and on the underside of the air switch.

If, like Hebe's this has deterioated, then the air won't get diverted to the correct position. I'm planning on buying some foam at some point (I suspect it'll have to be special high-temperature resistant stuff so that it's not a fire hazard), but at the moment I've just flushed the matrix, cleaned out the innards and refitted the heater. This time I switched the lucar connections around (it just does fit in Hebe if you're lucky).

The only tip I'd have is to replace any of the hoses you want to replace BEFORE you put the heater back in situ. I have some rather nasty scratches from trying (and eventually managing) to put the pipes on this morning.

Heater output has certainly increased, as has the airflow through the heater. I also bodged up an air filter to put on the fresh air input (made from some fine muslin). I hope that this is going to prevent insects from entering the matrix and improve airflow. When I rebuild Hebe, I'm going to try and make a filter to put on the front end of her intake pipe.

Nikki

Thanks Salty, yes I've had a look by removing the left side plastic "shroud" to which the small hose for feet warming connects. There is a triangular opening in the casing to allow air through to the hoses. The casing is common to both triangular holes and the lower rectangular hole. As there are no hoses connected to mine i've stuck a couple of pieces of foam into the holes (they are doing nothing anyway) so that the only opening is now the rectangular + the demist hoses of course. The sealing has also gone from around the directional flap, like yours. hence the leakage of air to the footwell when on demist only.

I suspect it'll have to be special high-temperature resistant stuff so that it's not a fire hazard

not really - the coolant system shouldn't get much more than 80 degrees so don't worry a lot. (It's not like an electric heater where parts can get to a few hundre degrees)

Thanks Nikki, there's definitely something not right and I suspect you are 100% correct. I'll wait until next year now befor removing the unit. Anyway at least in the interim I have a heater that does work (sort of) and it is better now than it was last winter. Yes I intend to renew the hoses at the same time. How is access? Not too good going by what you've said, scratches etc. Is it better to leave them connected until the heater is released? I've never renewed them on this type of heater, only on the earlier where ideally the speedometer has to be removed to get at the hose clips.

The thin layer of foam on the control flap on the late type
heater is only to seal off the air when the flap is in the 'off'
position. This is necessary because this late heater has no way
of shutting of the incoming fresh air to the heater itself It has NOTHING to do with the flow in the SCREEN or CAR
positions. If you suspect that the flap mechanism is out of position
then feel through the rectangular outlet for the following.
In the OFF position the flap should be hard up against its flange
i.e. you cannot push the flap any more towards the front of the
car via the rectangular opening. in the 'SCREEN' position the
flap should be dead in-line with the second flange which is easily
felt through the rectangular opening. If it is not then the flow will
not be correctly directed to the demisting vents. In the CAR
position the flap should be right back towards the driver. (When I
stripped my heater one side of the flaps' hinge was siezed solid
so it didn't sit in the correct position).
57...you will have to measure up with another late Minor to decide
where the two holes should be in the parcel shelf to direct hot air
to your feet. Well worth it. Regarding the 3"internal tube on my
heater, this means that the incoming air MUST pass through the
cylindrical fan because the end of the fan is in line with the end
of the tube so the air cannot just by-pass it. The heater radiator
if completely surrounded by strips of thickish foam so,if some has
rotted away it will allow air to emerge which has not had to pass
THROUGH the rad and therefore is still cold.

Looking at my Mini heater in the shed it looks like the foam does help to seal the flap when it is in screen position, are you sure it has no effect Willie??

Somone on here has used standard car sponge (for cleaning) cut thing & shaped to replace the foam on this flap & apparently it worked fine so no need for "high temp" stuff....

Yes I will probably measure up and cut the holes in the parcel shelf, for the two "feet warming" hoses Willie, when the whole thing is removed. It's also possible that there is a build up of muck, dust etc. on the air inlet side of the matrix plus the possibility of missing surrounding foam. Probably worth a treatment with the old kettle descaler on the water side too.

SALTY....Yes, I am certain that the only purpose of the thin layer
of foam on the control flap is to seal it better in the OFF position.
When the control is moved to SCREEN the flap has to move back
towards the driver until it lines up with the second flange in order
to direct air to the demisters. For the next stage (CAR) the flap
has to continue back even further(towards the driver). In order to
do this the flap has to pass THROUGH the second flange. So it is not
a precision fit in the second flange because it has to be able to pass
through it! If the thin foam was supposed to make the flap a better
fit in the SCREEN position it would have to protrude on all sides from
the flap. How long do you think this thin foam would last being
scraped against the metal edges of the second flange? The fact that
the flap is not a precision fit explains why you still get some air issuing
from the rectangular opening even when the car is on SCREEN. If you
want to do some definitive comparisons I will drop in on you at a
convenient time to compare cars? Just say the word. (I can also
bring you a piece of suitable thin foam).

Willie, Thanks for the offer! I might just take you up on that!!

The fan motor, like the starter motor, always turns the same way, regardless of wiring. I think they have field coils rather than permanent magnets, so when you reverse the current, you're also reversing the magnetic field and the motor spins in the same direction.
I know we're pretty well past that point now, but I thought I'd drop it in anyway.

Ben

The thing with the foam on the back of the air-directing-plate is that; although it undoubtably not intended to direct the air; it does help. Especially if (as in my case) the foam is slightly thicker than normal ('cos when I replaced it I didn't cut my foam anywhere near as thin as the original foam ).

This is simply because it means that although it doesn't seal, it does make the air-directing-plate thicker; and presumably makes it more likely that the air will go up the 'oles for the demister; and less likely that it'll make it round and out the footwell-vent-holes.

That said, I replaced all the foam in my heater, including the stuff that seals around the matrix; and also defuzzed my matrix, so it's hard to say how much improvement is due to what. Although, it must be said I'd now class my heater as "adequate"* which is nice...

* Previously it was "completely hopeless" (it did demist, but it certainly wasn't heating).

Benjy wrote:The fan motor, like the starter motor, always turns the same way, regardless of wiring.

Ben

No, there is a label on the motor casing which indicates that the direction of rotation is dependent on polarity.

Thank goodness for that 57 as I had always been led to believe (but wondered if I had imagined it) that when changing polarity you should reverse the heater wires, the problem we all seem to have is in measuring whether the output is different in one direction or the other.
As Nikki has just gone over to an Alternator have you noticed any difference in heater output as I bet you havent reversed the wires on the heater so far.

I'm sure I've read somewhere (could be MMOC tech tips?) that some wiper motors turn the opposite way when polarity is changed but it doesn't seem to matter and the connections can remain as they are.
I was sure my eyes weren't deceiving me when I recently reversed the heater motor connections, now seeing the label has confirmed that. Relief!

I think the wiper motor turns the opposite way when polarity is changed but it doesn't seem to matter

that will probably make it last longer as it will use the other side of the teeth on the worm and wheel

I've just edited and expanded my post a bit doobry since your post. Makes it less of a definite statement now. But, yes I agree with your comment.

Erm.......... if you are on about the wheels in the wheel boxes, it kinda uses both sides to push and pull! Unless you have rotational wipers that clean your bonnet too!!! Oh and an infinately long flexible shaft!

I assumed the worm and wheel in the wiper motor was being referred to. The wheelboxes are rack and pinnion.

I assumed the worm and wheel in the wiper motor was being referred to. The wheelboxes are rack and pinnion.

well said! ;-)
Yes - I was reffering to the worm and wheel 'gearbox' at the motor end. This will turn the opposite way, however it can only pull/push the cable whichever way it goes round.

The wheelboxes are a different matter altogether, but I see where the confusion arises as you can modify them to run on 'fresh' teeth when they get really worn.