The 'E' Type Forum

Hello gents,

I’ve recently fitted a Coolcat fan to my 3.8 and have kept the rheostat from the Kenlowe. Given this requires the sensor to be inserted into the top hose which I’m struggling to stop dribbling coolant, I’ve bought Coolcat’s switch which fits into the header tank. The question is, is switching on at 85deg ok? I have my fan set to come on as soon as the temp starts to rise from 70deg (shown on the gauge) so it never really gets a chance to get too hot. Is there a switch available that will fit Coolcat’s adaptor and is a lower temp, ie 80deg or lower?

Pete

I have Coolcats fitted on both my 3.8s.

I just use the OEM Otter switches sold by the usuals. Seem to cut in at about 75C. I reckon 85C is a bit high.

EDIT. Note that I always use a fan relay so the Otter doesn't see much current.

I installed a CoolCat fan on my '66 and ran it via the Otter switch with no problems. With this arrangement the car usually ran just slightly above 70C at all times. I believe the CoolCat thermal switch is from a VW Golf, and I felt that 85C/185F was a little on the high side, especially for southern California driving conditions. If you have concerns about the reliability of Otter switches, you can always fit a manual override switch, which is what I did.

Thanks guys, I actually have the old otter switch still in the header. I’ve never used it as the car came to me with the Kenlowe fitted. I might just wire it up and see if it turns the fan on (should’ve really thought of that earlier!) There is already a relay presumably fitted when the Kenlowe was installed.

Cheers
Pete

I’ve wired up my original otter switch but haven’t yet run the car up to temp.
Question: given these cars purge themselves if filled to the brim with coolant, how does the otter switch get a reading if it’s above the level of the coolant? My car maintains a level about 5mm or so above the baffle inside the header tank.

Cheers,
Pete

peters3103 wrote: ↑

Thu Jul 04, 2019 6:54 am

I’ve wired up my original otter switch but haven’t yet run the car up to temp.
Question: given these cars purge themselves if filled to the brim with coolant, how does the otter switch get a reading if it’s above the level of the coolant? My car maintains a level about 5mm or so above the baffle inside the header tank.

Cheers,
Pete

There seems to be enough depth of coolant in the tank. Certainly I don't have a problem in my 3.8 OTS. I fill the tank to the brim cold, run the engine, cool it and refill until there's no air in the hoses then let it find its own level. I haven't touched the coolant in that car for a couple of years.

Having said that I have the Otter installed in the manifold on my current resto 3.8 coupe. This was partially because I was concerned as you are and also because I was working with an intermittently faulty switch and moved it back into the manifold because it's easier to access. Probably means the fans come on a bit early but I don't think that's a problem in South Oz. I think later cars have the switch in the front of the tank or the front of the radiator.

Thanks Andrew, I’ll try it as is first - hadn’t thought of putting it in the manifold.

Cheers
Pete

peters3103 wrote: ↑

Fri Jul 05, 2019 2:41 am

Thanks Andrew, I’ll try it as is first - hadn’t thought of putting it in the manifold.

Cheers
Pete

I'm honestly not sure if that's a problem or not but so far it's been OK with this car although I haven't actually driven it yet :-). As I said I did it out of frustration with hitting my head while trying to sort out what turned out to be an intermittently faulty Otter switch (yet another quality item from the Usuals).

My thinking is that placed in the manifold the switch would potentially actuate the fan before the thermostat has opened and the radiator is hot. This might be a problem in very cold places but for us I reckon it'd be moot.

The manifold hole is for the switch for the thermostatic choke fitted to the Mk2's etc; they use the same manifold. Their switch conducts when cold and then shuts off when warm ie opposite to the Otter switch.

Yeah right Andrew, I had a 3.8 Mk2 for about 12 years and I thought the manifold looked the same. I owned it alongside a S1 4.2 E which is obviously different. Better for the fan to come on a bit early than late but bloody cold here in Canberra right now so might leave the otter where it is for the moment! I’m sure there’s plenty of E Types using the switch in the correct place without issue so we’ll see how it goes. I may even hide a “peace of mind”
switch inside the car for those edgy moments in summer traffic!

Pete

peters3103 wrote: ↑

Fri Jul 05, 2019 7:17 am

I may even hide a “peace of mind”
switch inside the car for those edgy moments in summer traffic!

Pete

Was your Kenlowe a two speed version? If it was, you can rewire the Kenlowe speed switch to be a simple on/off and it has the added benefit of illuminating whenever the fan is on.

Because I don’t have the original header tank or Otter switch, my Coolcat is driven by one of these- the temperature at which it kicks in is adjustable:
https://www.revotec.com/acatalog/Electr ... tting.html

Ray

My car now has a manual override to its Fosseway fan. The otter switch goes to one side of the fan relay and completes the earth connection when the temperature reaches 85 degrees (or thereabouts). We now have a second (manual) switch also connected to the same point on the Fan Relay which also completes the earth. As such, the fan will switch on either when the otter switch completes the earth connection or the manual switch. The wiring is well hidden and the switch is discretely under the steering column next to the milometer reset cable.

My car now has a manual override to its Fosseway fan. The otter switch goes to one side of the fan relay and completes the earth connection when the temperature reaches 85 degrees (or thereabouts). We now have a second (manual) switch also connected to the same point on the Fan Relay which also completes the earth. As such, the fan will switch on either when the otter switch completes the earth connection or the manual switch. The wiring is well hidden and the switch is discretely under the steering column next to the trip-meter reset cable.

Philk wrote: ↑

Sat Jul 06, 2019 5:09 pm

My car now has a manual override to its Fosseway fan.

I have done the same in one of my cars although I wired to the Otter switch which looks messy. I am going to change to your relay solution; much neater.

I put the Coolcat switch in place when I bought the fan but found that it seemed to cut in a little late for my liking and went back to the old Otter switch. Four years later everything is still fine.