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MG MGB Technical - 68 MGB GT. Heater blower

I have most of the bugs out of my car ready to safety. Only one annoying problem left to cure.After running the heater fo a couple minutes,it start to stop and start,stop and start.This car has been of the road for 15 yrs.I found by wiggelling the wires and fuse on the right side inner fender I could control it.I cleaned all the wire spades and fuses at that area.Presto the heater blower,ran for 10 problem,when I start the car,and turn on the blower it pulsates still. Help Thanks in advance. Rob Drope.
Allen Bachelder

The 12v supply to the switch is daisy-chained from the instrument voltage stabiliser. It's just possible that somehow you are picking up the voltage from the 'stabilised' side i.e. the light-green/green, and not the 12v supply side i.e. the green, as the stabiliser switches on and off about once per second. If not that you will need to check at the motor connectors with a volt-meter or test-lamp whether the 12v and/or earth is going on and off. If so then you will have to check at the manual switch, stabiliser, and fusebox to see where the intermittent break is occuring. The motor ground comes from the dynamo control box then the body ground nearby.

If the 12v and ground at the motor connectors are continuous when the motor is going on and off, then it is inside the motor. It is possible there is a damaged connection, which is heating up, opening up and stopping the motor, cooling down and closing again so restarting the motor, etc.
Paul Hunt 2

I believe that this is another example of the most common problem I've seen with Lucas fuse blocks, that is the rivet which holds the spade connectors on the bottom to the fuse clip on the top loosens and allows the metal to corrode and get poor connections. Wiggling the wires will usually correct the problem temporaraly, but for long term either replace the fuse block or as I do, solder the terminals to the rivet using a high wattage iron and a lot of flux to clean out the corrosion. I've done this on several fuse blocks and had no problems with them after this fix and this is going on 7 years now for my midget. I recommend even soldering the connections on a new block as a form of insurance against future problems.
Bill Young

It certainly happens (although 30 years isn't a bad lifetime) but *when* it happens it causes all of the circuits on the fuse to fail, so things like tach, wipers, gauges, brake lights etc. would fail as well the heater for the green circuit fuse.
Paul Hunt 2

This thread was discussed between 15/10/2007 and 17/10/2007

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