Cooling fan switch

[peters3103]

You’re too kind. Thanks Layne

[Philk]

I’ve just removed the additional “hot” wire from the relay and connected the unused green wire from the harness. The fan is now working only with ignition on. I’ll now replace my fan switch and all should be ok. I’ll still add the under dash switch and replace the relay with an original type for authenticity. Thanks for all your input chaps.

Glad it was of assistance. That's what the forum is for. When you do the wiring for the override switch, all you need to do is take one of the switch terminals to the earth connection under the dashboard (you should find at least one point) and then take the other to where the otter switch is connected on the fan relay. There may be a shared terminal on that you can use or you can simply use a two into one connector for both the override switch and the otter switch to connect to the relay.

[peters3103]

Excellent Phil, that sounds pretty straight forward. Thanks very much mate.

Pete

[peters3103]

A search of Jaguar relay part number C18122 at SNGB shows a 5 pin relay (SRB111). This is the one they list for the 3.8 cooling fan relay. Searching for C17338 listed at the same supplier has 3 pins and looks correct for the fan. Would this be the correct one to buy?

[Philk]

A search of Jaguar relay part number C18122 at SNGB shows a 5 pin relay (SRB111). This is the one they list for the 3.8 cooling fan relay. Searching for C17338 listed at the same supplier has 3 pins and looks correct for the fan. Would this be the correct one to buy?

Am not sure. I'd suggest you drop SNG a message to check. I've had a look at a spare 6RA I have here in the garage and that has 5 pins. Its Lucas model number is 33209-D though so does not tally with the original Lucas part number (see earlier photo above).

[peters3103]

Is this the correct location for the earth wires to be attached? (relay mounting screw) I relocated mine to this position but no earth. Could it be because the header is rubber mounted therefore insulated from the frame?



Pete

[mtnjag]

Mine is grounded to the inside corner bolt of the side frame to the picture frame. I restored my car but i believe that was the orig location. I think you are right about grounding to the header tank support being a poor ground.Lots of other possibilities if you don’t want to loosen the frame bolt but yes, I would move it. I always check my grounds with an ohm meter.

[peters3103]

Thanks Layne that’s exactly where I moved it too so fan operational again. I have also added the override switch under the dash and replaced the switch in the header tank so should be all good to go.

Pete

[mtnjag]

Great. I stuck the temp strips from Coolcats next to the temp sender on the intake manifold and they work really well. Put both the low temp and high temp strips and could follow the temp and compare to gauge. Nice ck of the gauge.

[Blue66]

I'd like to re-awaken this post as it is relevant to the fan problems on my '66 FHC.
Great weekend at Shelsley Walsh but got a little warm on the way home - electric fan not cutting in.

It has an aftermarket fan attached to the rad, and the PO fitted a CoolCats otter replacement switch together with a simple relay - although the 'heavy' feed side is fed by a loop from the 'low' feed terminal so effectively running all power through the old fuse-box (green?) feed (which seems to defeat the object of fitting a relay).

On investigation the fan still runs when powered directly, the relay still operates fine when energised, and I aim to feed the high current side with a new fused spur from the battery area, plus an over-ride switch in cabin. Once hot again I'll test the otter, but.....

My problem is the original feed wire gives very inconsistent voltage feed - initially at 4 volts with the ignition switch on, then miraculously at full 12.7v and triggering the relay, next time at 1 volt.... Even with engine running still a poor supply.

It appears that the original feed wire comes straight from the fuse box (number 6) via a green wire, which should be a simple 12v feed.

Is there a reason why I might not see a full 12v at that supply - ie other components in circuit?
Does this suggest it is shorting out somewhere and best no longer used?
I'm assuming the wire may be damaged along its length (burnt out by pulling the entire load of a fan?), but surprising to still have some current. What shoudl I test fro with a multimeter?
I could run a new green feed wire from the fuse 6 but hiding it and attaching to the old loom neatly is my concern. Any advice on running new wires?
Looking around for an 'ignition hot' source the coil is nearby and could be used with a fuse to invisibly feed the 'low' side of the relay, but this goes against keeping things close to correct Jaguar spec.

Thoughts appreciated, many thanks, Simon

[mtnjag]

Sorry, So just to clarify,
-The factory fan and relay are gone.
-You now have an aftermarket fan attached to the rad with an aftermarket relay with the coolcats temp sensor in the header tank.

-I think that should be a Ground activated Relay so wiring is a little different than a power activated relay. Check to see if its wired correctly.Same relay, just wired different.

-Did you check voltage at the fuse box source of the stock power feed wire ( feed wire disconnected) and does it match what you get on the wire at the relay end? If not very similar voltage i believe that would be a high resistance short and either track it down or abandon the wire.

-There is voltage loss in the factory wiring so it may not be up to actual battery level.

-The aftermarket fan attached to the radiator may pull as much as 20+ amps. Orig fan motor something like 7-8. Coolcats fan is supposed to be about 7amps. I have one, mounts in orig location works good, using battery buss power. Your little feed wire from #6 fuse is not adequate for the aftermarket fan. Adequate but not preferred for coolcats though.
-See how to properly wire the relay and sensor into the same circuit. Direct power feed from battery source buss is good practice.

[Blue66]

Hi there, thanks for responding. Yes the aftermarket fan is wired with a relay triggered to ground via the Otter, but in error the heavy feed is also drawing on the single fuse box feed - perhaps not surprising the wire is appears faulty. I will be using a heavy feed when I reconfigure it.

I haven't checked the voltage at the fuse panel so will do thanks. You confirm my concern that the feed wire is internally broken down somehow. I've checked the no6. fuse and it has continuity.

As I type this I realise that I also have a problem with inoperative brake lights and the horn which I'm sure were all OK a while back, and as these are all fed from the same fuse it may be more than coincidence, although the screen washers do work which I believe is also sourced there.

I will recheck fuse and power outlet....
Simon

[mtnjag]

Yes, sometimes those fuses look good but the failure is out of sight.
Make sure you are using the SloBlo Lucas fuses if fuse rating is at the stated Amp rating.
If using US fuses rating is almost half of the stated rating.

As in if Fuse box says 35Amps a US fuse would be about 20amps or so. Maybe someone has a conversion table.

You may be intending to do this but If fan is aftermarket and drawing maybe 20+ amps it shouldn't run from the fuse box at all. It should be a direct power draw from the battery buss.