As heater motors age, they tend to draw more amps than they should. Yours is probably drawing too much amperage causing the switch to heat up.
Remedy is to replace the heater motor and possibly the switch as the terminals get hot and oxidize.
To get heat in your 1976 MGB, first ensure that the engine is warmed up, as the heating system relies on hot coolant from the engine. Check the heater control valve to ensure it's open, allowing coolant to flow to the heater core. Adjust the heater control lever inside the cabin to the heat setting. Lastly, make sure the blower fan is functioning to circulate the warm air into the cabin.
From Den052 auto mechanic easiest way is to go to junkyard and remove part of the harness and maybe the switch if it is still good. Splice and replace as necessary. Keep in mind, check heater motor draws too much amperage and will burn out new switch. Usually the case!!!!!!!! Install new heater motor too (real common problem).
WEll, Since the ABS isn't as wire intensive as the blower motor and the blower motor is constantly turning, my first inclination woule be to disconnect the blower motor assuming a shorted out motor. This should be much easier than tampering with the ABS and much less detrimental if that isn't the problem.
Might be a bad heater control
coolant level could be low not letting it circulate through the heater core, causing it to blow cold. Also, if the coolant level is low it will in turn overheat.
you will find it in the heater box, also where the blower is. it is easy to remove.
The blower switch is the knob you turn on the heater control in the dashboard. If you are talking about the blower motor resistor, it is located in the passenger's foot well area, mounted in the heater box.
Check the fuse
Blown fuse. Burned out blower speed resistor. Faulty blower switch. Bad blower motor.
If a 2000 Grand Am sometimes has the heater blower working and sometimes it won't, the problem could be with the heater relay switch. The heater relay switch lets the heater blower know when to come on and when to go off. In most vehicles this switch is behind the glove compartment. This part sometimes gets corroded from condensation in this area.
Check to see if you are getting power and ground to the blower motor - if so blower motor is bad. If no power possibly fan switch or selector switch Also check the blower motor resistor, found in heater plenum.
the switch, or the blower motor resistor, or blower motor usually it the last two at one time
The heater blower switch and the electrical plug attached to it may be at fault. Remove the heater control unit from the dash and inspect the plastic electrical plug attached to the blower switch, you may see it has melted. The switch and plug is available from your local auto parts store.
The most common cause of the heater blower being on high only is the blower resister failing. The second most common problem is the blower switch going bad.
Blown fuse, bad heater blower motor control switch, bad blower motor, or a bad blower motor resistor pack.
In a 1997 Jeep Wrangler, the relay switch for the heater blower and motor is located behind the dash. It will be directly behind the HVAC knobs behind the dashboard.
The blower resistor is under the dash pad on the top of the heater box