Cooling fans relay burn
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.
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
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
Fortunately Brown & Gammons had a four terminal 6RA in stock
(part number 142169A replacing 589665).
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
also manual override switch. V8NOTE389