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MG MGA - Heater motor and fan upgrade

I have had a new "upgraded" heater blower motor and the more efficient plastic fan impeller on the back of my workbench for quite some time and I was just about to remove the heater unit in order to fit them.

My present motor has always been really noisy in operation and I suspect that the impeller is rubbing somewhere inside the heater body.

Whilst looking to see where the heater units mounting screws were situated, I noticed that the new motors mounting flange was significantly different in dimensions to the MGAs and it looked like the mounting holes wouldn't line up with the holes on the heater body.
Also, the mounting flange is sited about an inch further onto the motors body than on the original motor which would position the impeller about an in too far into the unit.

So it looks like I will have to somehow graft the MGA motors flange onto the new motor to get it to fit in the correct position.

I have read Barneys account of how he used silicone sealer to fix the MGA flange to this motor but I would rather try to either weld, rivet or even clamp the flange to the motor.

Has anyone ever tackled this job? I would appreciate to hear if anyone has had any experiences with this.

Cheers
Colyn

This picture shows the new motor and the impeller.



Colyn Firth

This picture shows the position of the flange which is approx halfway along the new motor.


Colyn Firth

A picture of the MGA motor fitted to my heater. The flange is mounted much nearer to the end of the motor.


Colyn Firth

Colyn,
on a tangent, I found my uprated motor on my midget worked a bit better when wired backwards (and I hadn't put the impeller on the wrong way round and I *think* the existing wiring is correct).

Obviously check your motor is a Timmy-two-ways before testing on a live battery supply as I wouldn't want to be responsibly for a burnt out motor.

I hope I didn't get too technical with my jargon. :)
Nigel Atkins

Colyn

I put one of those bilge blowers in the heater trunking. Shifts a lot more air than the standard fan into the car. It's the one that many use for carb cooling in the trunking on the other side, but I found unnecessary.

Steve
Steve Gyles

Colyn

You could try making 3 stand-off spacers, tapped in each end, Fit one end onto the heater body and attach the new motor to the other end. You would have to incorporate an annular seal at the heater body end to seal the new motor to the heater body.

Cheers

Dave
Bolney Coupe

Nigel
my original MGA motor is a different design to the replacement motor in that it only runs in one direction regardless of which polarity it is connected.
The replacement motor though is polarity sensitive and will run in different directions depending upon which way you connect it.
So if I do fit it I will have to be careful how I connect it up.

Steve,
I had considered using a bilge blower hidden away inside the air intake pipe but I am a little discouraged by the noise they make, ie. reminds me that the living room carpet needs vacuuming when I get home :^)

Dave,
that's not a bad idea, it shouldn't be too difficult to make up three spacers and fabricate a new flange to seal onto the heater unit.

I was looking at the more complex option of drilling out the spot welds on the flange/ motor body and then rewelding it into the correct position nearer the end of the motor.
Quite a few pitfalls involved in that course though and I so like your solution much better.

Cheers

Colyn
Colyn Firth

Colyn, that's what I mean, try both ways mine is wired the wrong way and worked better (check with smoke or scent test).
Nigel Atkins

Will do Nigel,
So unless I have seriously misunderstood what you meant by "scent test", assuming that once the heater is re-installed, I would then have to drive the car at walking pace along the sidewalk following very closely behind a likely attractive and well dressed subject who was smoking.

Then once I had positioned the fresh air intake as close to them as possible, switch on the heater blower to see if the demister vents permeated the interior of the car with aroma of tobacco smoke and Chanel No 5?

Mind you this is South Yorkshire and so easily the smoke is just as likely to combined with the aroma of donar kebab😊.

I just have to work on how to explain my antics to the police after they have arrested me for kerb-crawling😀

Colyn
Colyn Firth

On a slightly more seriously note, I seem to recall that someone had filled all of the extra space inside the heater box with polystirene foam to make the airflow following a more efficient path through it.

It apparently increased airflow significantly.
I just wondered if anyone else had done this.

Sounds a sensible idea but I wondered what kind of foam material would survive the heat plus the petrol and oil fumes in the engine bay.

Cheers
Colyn
Colyn Firth

Colyn

If your heater is blowing engine and petrol fumes you have a severe leakage issue. As you know the solitary air feed to the unit is via the long trunking to the snout.

It's summer, even in Yorkshire. Heater should be off or blowing cold and the top should be down. You must be doing serious forward planning to be addressing toe warming right now.

Steve

PS. I cannot hear the bilge fan in that long trunking while moving. Too much wind blast round my ears!
Steve Gyles

Steve, Colyn shouldn't be able to hear the bilge fan either, as he likes the pedal down near the floor..LOL
Gary Lock

What is the diameter of the new motor?

I think the idea of using a spacer is probably the way to go, maybe you could get Mr Gyles to put his lathe to use and make one with a suitable mounting flange.

BTW My new 1950 is now running beautifully and I CAN year the bilge blower over the engine noise, but that's maybe the combined prowess of Messrs Betson and Burgess has produced me a VERY smooth running engine and my car now doesn't drip oil at all. Will run it for a month or two and then fit the supercharger.

It's a bit scary now, so I want to test things a bit before going the final step!
Dominic Clancy

Bear in mind to get the full heat and fresh air through to the cabin/windscreen always have the trunking fresh air flap/valve fully open even in coldest winter and not to use it as some sort of secondary temperature control.

The more fresh air you get through the heater box the more you have in the cabin, the more fresh air you get through the heater matrix the more heat you will get in the cabin, even if that air starts out cold, as it passes through the matrix it will be warmed, the greater air volume going in the more heated coming out.

I've tested this system through over 20 years and tens of thousands of miles of winter use, keep the fresh air flap fully open.

The only time you migt want to shut the fresh air valve flap is when in dirty traffic (particularly Aldi, sorry Audi, diesels that seem particularly to be soot fog providers).

To get the most fresh air the trunking needs to be properly aligned at the front so that it's totally unrestricted and heater box mounting seal in good condition.

To get more heat you could also try putting a foam strip around the heater matrix so that the fresh air all passes through the matrix rather then any going around, again the heater box mounting seal needs to be in good condition to stop loss to engine bay.

The blower should only be need when stationary or at low speeds (below 20-25mph in my Midget) after those conditions it's just noise and battery drain. Also bear in mind it can only move the fresh air that's available so keep the fresh air flap fully open, trunking unrestricted and seals, er sealing. :)
Nigel Atkins

Nigel and Steve,
my project is really aimed at getting more airflow through the heater and into the car, probably more for ventilation than for improved heating.
I almost never close the fresh-air vent, in fact the last time I did this it had become very stiff and I ought to really get around to lubricating the linkage.

I don't get much in the way of engine fumes into the car, at least, non through the air vents and I have spent a lot of time sealing all of the gaps and holes in the front bulkhead.

I'm afraid that Gary is correct, my exhaust does tend to drown out most other MGA sounds.
I think its more often known as HRF syndrome Gary, Heavy Right Foot! :^)

My 5-brg 1950cc engine does go really well though, the way it accelerates is a bit scary at times.

It is surprisingly smooth in operation too, it feels more like a turbine than a straight 4.

My previous 3 brg 1850 cc engine was much noisier in comparison with lots more valve train noise, it is probably down to the new 1950 cc engine being much better balanced.

Dominic, you are probably in for a real surprise when you fit the supercharger to your engine, I can't wait to here about how it goes.

Cheers
Colyn
Colyn Firth

Colyn,
have a look at the fresh air heater valve flap and check it's at the full open position when set for such (a couple of longer term MG owners had the flap set 180 degrees out) and that there's no debris build up if you have the wire mesh between the trunking valve housing and heater box, a surprising amount can build there. If you don't have the mesh perhaps the heater matrix could have the debris restricting your fresh air flow (and heat).

With the Midget heater matrix some show the long foam strip wrapped around them and some don't, I don't know why, but I think it helps with concentrating air flow (and again heat).

Oh and something I forgot last time, to help seal the heater box and get more air flow - grommets in the heater box face, around the matrix pipes

Whilst you're there you could lubricate the flap spindle and work the lubricant in, I'm never sure about lubricating cables too much in case that just holds grit and muck to them.

I think the heater boxes are too big and not ducted directly enough to be very efficient plus they have no really insulation so filling the extra area could prove to be more efficient.

For fuller insulation you'd also need to insulate the inside or outside the box walls not covered by the filling, some sort of insulating paint or cover material inside and/or outside.
Nigel Atkins

Thanks Nigel,
I have seen a series of pictures somewhere online where someone had packed the heater box, leaving just enough space for the air to flow through the fan and not eddy around in the corners of the box. Its just a case of deciding which material would work best for this.

Once I get the box off I will try to do some sort of back to back runs to see what difference the new impeller and motor make to the airflow rate.

Dominic, you asked about the size of the fans, well both of the motors are 3" in diameter, well maybe a thou or two smaller than that.

Cheers
Colyn
Colyn Firth

Yes I wonder if a more powerful fan might be a bit self-defeating as it just bounces the air around more. My uprated fan and impeller make a lot of noise but I'm not sure they push much more air than the standard set up in good condition.
Nigel Atkins

Try looking up 3 inch ducting catalogues for a flanged fitting that you can slide the motor into, and use the flange for mounting to the heater casing.

Not an easy job getting a heater in and out of an A, lots of tiny tiny screws around that lower flap.... and those heater control cables are the worst job on the car. I ***REALLY*** recommend getting ones that use the original push-on knobs and a slotted collar rather than the preformed ones that use a nut on the back of the heater bezel. Then the back of your hands won't look like you have been attached by a rabid cat.

But it IS possible to change the hamster wheel with the heater still in place if you remove the inlet flap assembly in the engine bay. You just have to loosen the nut and pull really hard on the old fan through the hole where the flap mounts. There may even be space to get the motor out too if there's no hamster wheel on the shaft. The new wheel just pushes on. I have installed a number of the new wheels like that, and they are an upgrade even without a new motor.

Your noise is probably caused by something foreign in the fan assembly, but you will see when you take the old fan out

Dominic Clancy

Thanks Dominic
I have had a quick look for 3" ducting/flanges but not seen anything suitable yet. I will keep looking.

I then thought I could possibly use one of the flange fittings that is fitted to the front of the MGA heater unit where the fresh air enters, but then I remembered it was an angled fitting and so it wouldn't work.

Maybe there is a 90 degree flange on a different MG model, I will research this.

Cheers
Colyn
Colyn Firth

Just noticed that the air hose is around 4" diameter so I think we can forget that idea. :-(
Colyn
Colyn Firth

This thread was discussed between 20/05/2019 and 22/05/2019

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