Troubleshooting the E-Type radiator fan

Last September, the electric fan on the E-Type stopped working.   This is a particular problem in the E-Type as there is no mechanical fan.   At the time I assumed the coolant temperature sensor had failed.   It would seem that many people have trouble with these sensors.   I knew the coolcat fan was fine, as it roared into life when I applied 12v directly to the fan.

When I had bypassed the switch, I broke one of the connectors off the Lucas relay that controls the fan.   Therefore, I ordered an upgraded temperature sensor from Coolcat.   I also ordered a new Lucas relay from XKs Unlimited, trying to get the same one I already had.   This was for two reasons.  Firstly, it looked good compared to the normal black square relays, and secondly the mounting tab was already there and in the right place.

While I waited for these parts, I bypassed the temperature sensor and let the fan run all the time.   It was summer in Sydney so it would have run much of the time anyway.   On a drive in November, the fan failed again.   This time it had blown the fuse.    I resolved to fix this properly before I drove the car again.

The way the relay had been wired in baffled me.   It was using the same source for both the main 12v feed and the switching source.   Even though the E-Type radiator fan does not draw very much current, it seemed odd to wire it up this way.   My car has the Coolcat fan, which draws similar current to the stock fan.

I therefore ran a 12v power source with in-line fuse to the relay and used the car’s normal power source just to switch the relay on.   This should prevent the fuse from blowing.    I started with a 10A fuse as the fan is rated at 7, but it blew this so I went to a 15.  It would appear that the starting current is a little higher.

Upgraded Relay

Unfortunately, while the picture on the XKs Unlimited website showed the same red cylindrical relay I had previously, the one that arrived was a regular black square one, except it was made by Lucas.    I was about to drain the coolant on the header tank to replace the switch, when it occured to me to test the one I had first.  I knew my original problem was either switch or relay.   Since I had broken the original relay disconnecting it, it made sense to test the switch with the new relay.   Lo and behold, it worked fine.    I now have a spare sensor, and a working car.

After that, I took the car on an extended drive up to Gosford via the old Pacific Highway and the fan performed as it should.   I made sure I included a spare fuse in he car, but luckily I didn’t need it.

Until I can source the correct relay, I have used a zip tie to attach it to the mounting point.   At that time, i will try and tuck in the new red wire a little better.    The sticker on the radiator header tank shows the temperature.   Great for checking the fan sensor is working!

Lucas Relay

It was good to get behind the wheel of the E-Type after a couple of months.  Even better that it didn’t overheat.    I continue to be very happy with the diff ratio change I did.   Third gear is now a useful gear for twisty roads, like it should be.    In addition, the halogen lights are excellent, better than even cars from the 80s.   The E-Type series one is known for poor lighting, bug once its upgraded to Halogen it’s great!

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