Heater (late square type) Overhaul

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svenedin
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Re: Heater (late square type) Overhaul

Post by svenedin »

Hello Bill,

The front plate isn't completely flat. It has a shallow return on the edges which means the plate is stiff. There is a screw in the centre of the plate at the top which is hidden with the heater installed with no access to remove it. I don't think you would be able to fit the ears without dropping the heater down. In the photo you can see the heater dropped down with the front plate still on. When the car was repainted they didn't mask off the part that is hidden behind the dashboard so it got Smoke Grey paint on it.

Dropping the heater is a horrible job. I would suggest the following (take a deep breath, have a good head torch):

1) Disconnect the battery (live wires behind speedo)
2) Remove screw either end of parcel shelf crash bar and lower shelf down
3) Loosen speedo retaining screws on either side, accessed through inboard hole in each glovebox
4) Remove 2x machine screws, nuts, washers, split washers that hold the top of the heater box onto the dashboard. These are accessed with the speedo pulled out. The screws have Phillips heads and are 2BA. A 2BA ring spanner is needed.
5) Loosen and remove 2x nuts, washers each side holding the heater bracket to the bulkhead. Remove brackets
6) Free the top of the heater box from the dashboard and then it should start to drop down.


Photo shows 1 of 2 heater retaining screws with 2BA nuts

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Front plate showing concealed top centre screw


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1969 1098cc Convertible “Xavier” which I have owned since 1989.

Stephen
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Bill_qaz
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Re: Heater (late square type) Overhaul

Post by Bill_qaz »

Thank Stephen, I'll try to flex the plate enough with top screw still in place to get the ears under the edge, if not they will not be getting fitted :lol: too much work :wink:
Can I ask what are the domed black piece in each ear, are they blanking grommets?
Regards Bill
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svenedin
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Re: Heater (late square type) Overhaul

Post by svenedin »

Yes there are domed rubber grommets. I have no idea what the purpose of them is. The originals had shrivelled and decayed.

Stephen

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IMG_8526.jpeg
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1969 1098cc Convertible “Xavier” which I have owned since 1989.

Stephen
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svenedin
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Re: Heater (late square type) Overhaul

Post by svenedin »

More heater news. I have been given another heater box free of charge, that came from a scrapped late Traveller. As I already have a functioning heater in the car this one is for experimenting to try to improve the performance whilst keeping it looking exactly the same. This heater needs a full strip down to bare metal and rebuild anyway. It should be possible to fit a more powerful motor (but with the same footprint) and a slightly larger centrifugal fan. The standard Smiths "squirrel cage" centrifugal fan is 4" diameter but there is some leeway for a larger diameter fan. A motor that spins at a higher rpm would shift a lot more air and a 2-speed option might be nice too. Autumn projects here we go.

Stephen
1969 1098cc Convertible “Xavier” which I have owned since 1989.

Stephen
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Bill_qaz
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Re: Heater (late square type) Overhaul

Post by Bill_qaz »

Out of interest the fresh air intake, elephant trunk, comes in the drivers side what does the panel on the opposite side look like,
on your heaters?
Mine seems to have a duplicate input taped over.
Regards Bill
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svenedin
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Re: Heater (late square type) Overhaul

Post by svenedin »

Hello Bill,

On the side that the elephant's trunk joins the heater box (the right hand side as you are sitting in the car looking forwards) there is a rigid blue plastic pipe that the heater duct joins to. On the other side, there is a very similar hole but the motor goes into that hole.

Stephen


Air intake side (before refurbishment and with the heater matrix removed, heater matrix pipes exit on this side)


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Motor side (after refurbishment)

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1969 1098cc Convertible “Xavier” which I have owned since 1989.

Stephen
ManyMinors
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Re: Heater (late square type) Overhaul

Post by ManyMinors »

svenedin wrote: ↑Mon Oct 19, 2026 6:48 pm Yes there are domed rubber grommets. I have no idea what the purpose of them is. The originals had shrivelled and decayed.

Stephen


IMG_8547.jpegIMG_8526.jpeg
I think the rubber grommets (possibly the same as those which stop the door handles from hitting the bodywork?) are to stop the glovebox lid hitting the heater.
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svenedin
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Re: Heater (late square type) Overhaul

Post by svenedin »

ManyMinors wrote: ↑Wed Oct 21, 2026 9:45 pm
svenedin wrote: ↑Mon Oct 19, 2026 6:48 pm Yes there are domed rubber grommets. I have no idea what the purpose of them is. The originals had shrivelled and decayed.

Stephen


IMG_8547.jpegIMG_8526.jpeg
I think the rubber grommets (possibly the same as those which stop the door handles from hitting the bodywork?) are to stop the glovebox lid hitting the heater.
Aha! That sounds sensible. I used bottle jack rubber filler bungs as the perfect sized replacement.

Stephen
1969 1098cc Convertible “Xavier” which I have owned since 1989.

Stephen
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svenedin
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Re: Heater (late square type) Overhaul

Post by svenedin »

Incidentally, I had noticed the motor is offset from the centre of the case. I hadn't realised that this forms a scroll, like the spiral of a sea shell or a turbocharger. I presume the aim of this is to speed up the air flow as it meets the heater matrix. Very clever design.

Stephen

Red Line Tracing a Blower Wheel Base.png
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IMG_8586.jpeg
IMG_8586.jpeg (1.77 MiB) Viewed 39 times
1969 1098cc Convertible “Xavier” which I have owned since 1989.

Stephen
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