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Cooling fans relay burn out
On returning from a run in heavy traffic Victor Smith could
not hear the cooling fans running so checked the engine bay
and found the cause. It's a service check many V8 enthusiasts
could make to avoid a similar problem.
(Mar 12)
On
returning from a run in heavy traffic I was about to back into
the garage and noticed I could not hear the cooling fans running.
As V8 enthusiasts know when the car is not moving and the twin
cooling fans are running they make a very audible roar. So my
first check was the water temperature gauge (that was at around
5pm on the dial so the Otter switch would normally have cut
in) and then I checked the manual override switch by my left
knee as I was reasonably sure I had thrown the switch when held
up in a traffic queue. Yes it was still on. So I opened the
bonnet and earthed the spade to the Otter switch terminal to
earth on one of the bolts of the Otter switch flange - the fans
did not come on. So engine off and ignition off.
Brown wire from the fuse box to the cooling fans relay terminal
"C1"
Leaning over the offside wing my search worked from the fuse
box along the brown wire carrying the power supply to the fans
relay and there, on the other end of that wire, I saw the spade
connector to the terminal on the underside of the 6RA relay
was burnt nearly to a cinder.
I removed the relay and could then see the underside and the
terminal was almost hanging from a hole burnt in the base. On
inspection the "C1" terminal showed signs of some
corrosion, so the likely cause was an increased resistance through
that connection which, with the relatively high current drawn
to run the twin fans, must have generated a great deal of heat.
The relay is rated 12V 20A.
I then went off to my spares bag and found I had a new "6RA"
relay so began fitting it until it dawned on me it was a three
terminal 6RA and not a four terminal 6RA which I needed to make
the replacement. Both relays have "6RA" on the side
of the unit, so if you need to buy one do check you get the
right one!
Fortunately Brown & Gammons had a four terminal 6RA in stock
(part number 142169A replacing 589665).
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Original 6RA cooling fans relay
Three terminal 6RA relay with no "W2"
terminal
Once the relay and a new section
of brown wire (7.5
cm long BTW) with insulated
spade connectors crimped to each end was replaced it was found
the Otter switch (part number BHA5252) also needed replacement.
Crimping is best done with
a specialist crimping tool.
So a worthwhile preventative maintenance item is checking the
spade connectors at either end of this brown wire. After 35
years preventative replacement is worth considering together
with a replacement Otter switch because reliable cooling is
essential with a V8 engine in an MGBGTV8 engine bay.
See also a NEWS item on the Otter switch. More
See also manual override switch. V8NOTE389 |
