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MG MGA - Heater Squirrel Cage Fan

I've ordered the new motor but Moss says the squirrel cage fan is unobtainium and I'm having a helluva time getting the old squirrel cage off the old motor. I've removed the allen screw and tapped the hell out of the shaft but it won't come out of the fan. Applied copious hean and no joy. Have it soaking in PBBLaster overnight and am hoping for better results tomorrow.

Is there a secret to removing the squirrel cage from the motor? I'' join the fraternity and learn the secret handshake if you'll just tell me how to remove that squirrel cage without destroying it.

Thanks.

Jud
J K Chapin

Jud,
If it's an original MGA fan, it helps to remove the hex nut on the spindle. It is a compression nut that holds the fan onto the shaft.

Mark
Mark Wellard

Maybe it's not original because there is no hex nut, just the grub screw holding the center hub to the shaft. At least I think that's what it is. There is a round center boss that I don't think unscrews. I'll take a picture later today so you can see it.

Thanks.

Jud
J K Chapin

Well, we got it off. Had to complete the destruction of the motor to do it but the motor was toast already (the armature had completely disintegrated). No compression nut or threaded shaft, just a grub screw against a flat part of the shaft. Penetrating oil and twisting the cage while holding the shaft still did the trick.

Jud
J K Chapin

Use a fan from an MGB. Plastic, but it delivers more air
Dominic Clancy

I read, or quite possibly misread, that because the motor is on the front and perhaps spins the opposite direction from the MGA motor (actually it would spin the same but is just turned around), the louvers on the MGB fan are the reverse of the MGA fan and won't work in an MGA.

Does anyone really know?

Thanks as always,

Jud
J K Chapin

I fitted an MGB motor to my MGAs heater box along with the uprated MGB impeller and it works fine, the air flow is vastly increased.


I also modified the inside of the heater box to fill up the big space on the motor side of the box and also modified the ducting that directs the airflow out of the unit more efficiently.
I would say that the airflow out of the heater unit has at been increased by at least three times.

When I first tested the modified heater, I pulled the demist knob and the airflow from the demister vents actually blew my hair around! Prior to this, you could barely tell if the blower was on or not.

One other thing I did was to temporarily connect the heater motor up using a much thicker wire than that originally fitted, this instantly increased the motor speed by around 10 to 15%.
So I installed a relay to make a permanent job of this and I noticed that this also prevented the heater fan switch from running hot like it did before.

I have attached a couple of pictures which show some of these mods.

I wrote an article for Safety Fast a few years ago about this project and I would be happy to email anyone a copy of this if they wish.

Cheers
Colyn





Colyn Firth

This pic shows that I had to use the motor flange from the MGA motor to get the MGB motor to fit in the correct place.

I used a small hose clip to tighten the new impeller onto the motor shaft, it didn't really need two clips to fasten it securely, but I thought that using two of them fitted opposing each other would solve any imbalance issues.
Cheers
Colyn

Colyn Firth

Jud,
The MGB fan does turn in the opposite direction. You need to source one with the MGA profile unless you are making a twin cam heater, which is reversed.

Mark
Mark Wellard

When I fitted the MGB fan motor to my MGA unit heater, I had read on MGA Guru that the new ones supplied by Moss would run in reverse if you simply reversed the wires. Something to do with it having a permanent magnet field.

So, when I got mine from them, I checked to see if this was actually the case and it was, reversing the wires did reverse the rotation of the motor. It runs equally well in either direction.

The blades on the MGB plastic impeller are oriented in the same direction as those on the original MGA metal fan but are obviously much more efficient and they move a much greater volume of air.

I have attached a pic of the original MGA motor and fan.

Also, here is the link to the relevent MGA Guru page.

https://mgaguru.com/mgtech/electric/et211a.htm

Cheers
Colyn



Colyn Firth

Colyn and friends, we completed the installation of the new fan motor today. We confirmed that the motor runs equally well in both directions that changing directions is simply a matter of reversing the wires. The motor sold by Moss appears to be a good motor but it is not the same as the original. It's a bit linger but does just barely fit between the heater box and the firewall.
Also, it is not designed to be mounted with a faceplate. It has mounting ears mid body that can't be used and the longitudinal screws through the motor are just barely long enough to hold the mounting plate. The face of the motor where the shaft comes through is not flat and this required us to enlarge the center hole in the plate (see pic of my neighbor enlarging the hole using a metal cutting burr on my router table).
Once the face plate was on the motor (we also had to grind a flat side on the motor shaft for the grub screw) reassembly was straight forward, i.e., you can't reach anything under the bonnet or under the dash in a MGA without being a circus contortionist.
The old fan switch on the heater control lever was also toast but, fortunately, I had ordered a new one just in case.
Good news: The new fan blows lots of warm air. I'm driving the MGA up in the mountains in the morning and the starting temperature will be about 30F. No top.
Jud


J K Chapin

This thread was discussed between 28/11/2024 and 04/12/2024

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