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80 MGB heater fan switch

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Richard1 Avatar
Richard1 Richard Marks
Canon City, CO, USA   USA
I need to replace tyhe heater fan switch on my 80 MGB. Can anyone help with a quick & easy way to make the switch (so to speak)?

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Edmonds, WA, USA   USA
The easiest way is to spend $20 and get the right switch.

If you truly want a different switch, I suggest you look at the wiring diagram for the heater switch and understand how the switch works.

It takes power from the green circuit and on low sends power to the wire in series with a resistor in the heater box. I can't remember If it's the green/yellow or the green/brown.

On high it powers both of the output wires, with the wire without the resistor providing full power to the fan and the wire with the resistor essentially being bypassed but still getting power.

The hardest part is finding one that fits in the dash without cutting and doesn't look out of place, if that bothers you.

course2kid Jeffrey Johnson
Fountain Valley, CA, USA   USA
1979 MG MGB "Lucy (Lucifer)"
Attached is a pic of the switch. It is held in place by two metal spring tangs (on top and bottom). The switch is a pretty tight fit in the rectangular hole in the steel back of the dashboard. If you can get your hand back there and sqeeze both metal tangs, it'll just pop out.

You may be able to just pry/pull the switch out. On the other hand, if you have a new replacement switch and the old switch is definitely broken, it may be easier to pull the toggle button off the old switch, jam a screwdriver into the switch (battery disconnected) and break it so you can push it out the back or pull it out the front.

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hump2 Avatar
hump2 Barry Humphrey
land o lakes, FL, USA   USA
Most of the switches on my 79B have those tabs. I had a heck of a time getting my hand in to hold the tabs to remove the switch on each. Solution was to bend the tabs back and forth until they came off and put the switch back in. They do not move at all in the dash and they sure are easy to take out now when I need to get at the back of them.

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Fogliner Avatar
Fogliner Mark Vanherd
Port Clements, BC, Canada   CAN
1974 MG MGB
John Twist has a video somewhere on his youtube channel showing his tool for the job.

It consists of a 3/4 inch piece of steel pallet strapping bent into a squared off C shape piece that you insert so it depresses those tangs from the top and bottom.

The steel strapping is stiff enough if bent correctly, its handy if you have another switch to model your tool around so it will be correct when you are reaching back there with it in one hand and trying to slip it over the switch.


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