Thanks, Kelvin and others who responded. Kelvin, your explanation is great
and clarifies several points.
But... I think I've got the problem narrowed down to the circuit breaker in
the feed line. I've replaced it, and now need to check that the switch and
fans will work properly. Guess I'll go for a drive to warm it up.
Again, thanks to all who replied.
Howard
-----Original Message-----
From: owner-mgs@autox.team.net [mailto:owner-mgs@autox.team.net] On Behalf
Of Dodd, Kelvin
Sent: Tuesday, July 12, 2005 9:29 AM
To: Howard Battan; mgs@autox.team.net
Subject: RE: MGB cooling fan thermostat
Howard:
Short the switch leads together as Mike suggested. The cooling fans
should then come on. That determines that the switch is bad, which is a
pretty common occurrence.
Buy a new switch and install it. FWIW the Moss ones are in Lucas boxes
and are supplied with sealing bush, but the original manufacturer is
Intermotor.
Two things to understand as there has been a lot of misinformation about
these switches.
1. The reason the switches pop out is low water level. Steam builds up
in the raised section of the radiator and the switch pops out. If the
water level is over the switch as it should be, the original bush will
hold it just fine.
2. Premature switch failure is often due to poor condition cooling fan
motors. When they start to drag the current required for operation goes
sky high and the switch "canna take it anymore".
The later switch has spade terminals and a retaining clip. This clip
will not hold the switch in under low coolant conditions as it only has
light spring pressure. The switch is only available as an OE part,
hence the high price. Supposedly there is a difference in the radiator
mounting hole, but I have not been able to see one yet. The diameter of
both switch bushes is the same. Often people will suggest using a
mounting bush originally supplied by Jaguar which is a bit deeper than
the MGB one, but again the problem is steam build up, not the bush.
This is one of the areas where installing a relay will increase the life
of the switch and the efficiency and life of the cooling fan motors. On
late cars the factory also installed a circuit breaker on this circuit.
|