Morris Minor Owners Club

The white wire from my heater is not connected to anything under the bonnet, where does it normally go?

White is usually the ignition switched unfused supply to fuel pump, coil, and ignition warning light, taken from the A3 terminal on the fuse box. My preference is to feed it from the fused side A4.

The black is connected to the top left of the fuses, and white is just going to nothing.

Farvie wrote: ↑Thu Jun 05, 2025 4:04 pm The black is connected to the top left of the fuses, and white is just going to nothing.

By 'convention', Black should be earth connection, White should be power.
Usually changing a car from Pos Earth to Neg Earth does not affect the heater, but some models, due to the way the motors are wound, will rotate the opposite direction if the polarity is reversed.
If I recall correctly, you've said your car is Pos Earth....

If this was factory fit, then it was intended for a Pos Earth car, but if it wasn't...
If you've got the Black going to a supply connection, then connect the White to an Earth and see if the Blower blows out towards the inside of the car.
If it doesn't, then reverse the connections.
You can always then reverse the connections to be Black Earth, White Supply and see what happens; but ultimately it just needs to blow air into the car.

Hi Berni,
Thanks for the info, will give that a try.

Thank you

So I had a quick try, the white wire I touched on the big nut on top of front suspension unit and it was sparking from that.

Was the switch on or off at the time? If on, then did the fan run? It is not uncommon for sparks to appear when making a connection in this manner, it is not as clean as an on-off switch.

If the switch on the heater is faulty, then you could bypass that in order to test the motor. As previously, I recommend using a fused supply to protect the wiring if there is a fault in the heater.

Farvie wrote: ↑Thu Jun 05, 2025 4:04 pm The black is connected to the top left of the fuses, and white is just going to nothing.

Farvie wrote: ↑Thu Jun 05, 2025 10:26 am The white wire from my heater is not connected to anything under the bonnet, where does it normally go?

I'm wondering why both wires are under the bonnet....

The Earth should have been to local bodywork inside the car, the Supply should have been picked up from a green wire multi-connector under/behind the dashboard, which also feeds the Oil Pressure Switch....

I'm going to investigate more today, trace the wires from the heater and see where they actually go, as both wires under the bonnet are black, but have tape on them saying heater white and other just heater.

Farvie wrote: ↑Fri Jun 06, 2025 9:49 am I'm going to investigate more today, trace the wires from the heater and see where they actually go, as both wires under the bonnet are black, but have tape on them saying heater white and other just heater.

Sounds like a good idea. The Woes of discovering past owners efforts.....

I've had my car almost 8 years and I sill occasionally find a new issue.
I recently found the rear seat squab has no attachments at the bottom; it's just sitting there held by 3 screws in it from the boot.....

It's scary what others do.
Right heater works if I connect white to fuse where the black was and earth other to body, Now can i run it this way or what would you suggest? My glove box inners are out as reshaping them, so have easy access as steering wheel off too. Cleaned up fuse area

UPDATE!!

wire it to light switch and earth wire to body, only thing is don't need ignition on to power it, not sure if that's OK or not?

Have you got the Workshop Manual with the wiring diagrams?

It's supposed to connect as shown, slight variation on some models. But basically a connection with 3 or 4 green wires.
.

That diagram goes over my head lol
I need pictures or videos, I'm a bit thick like that
The way I've done it bernie, is it safe? Or do I need to change it.?

Farvie wrote: ↑Fri Jun 06, 2025 4:03 pm That diagram goes over my head lol
I need pictures or videos, I'm a bit thick like that
The way I've done it bernie, is it safe? Or do I need to change it.?

OK.... no point in showing you what Basil's is like as he has an after market Tudor Heater.
As originally fitted, the Smiths one should have the supply picked up from one of these multi connectors, with green wires in it.
https://www.autoelectricsupplies.co.uk/ ... ble-common
You should find it up behind the dash.

If the wire is already routed out to the fuse block, it can be connected to where the green wires are.
NOTE - That screw head at the middle bottom with no connections on it is common with where the 3 green wires are (see the little strap connecting them). So you can connect the heater supply wire to that.
Those are the circuits controlled by the Ign Sw.
.

Many thanks bernie, I'll disconnect the wires I did on light switch and earth wire, and re route them back under to bonnet and connect power to the greens and earth to body.

Thank you