cooling fan operation temperature

William makes a good point here. The Series III E-Type otter switch is located in the radiator outlet hose. That means that it should turn the fan on a a considerably lower temperature than cars which have the switch near the thermostats. If you have 180F thermostats, you would reasonably expect a temperature drop of around 20F through the radiator, so the exit water would be around 160F. The fans should turn on around 175-180F to keep you safely in range. 95C (203F) sounds 'way too high to me.

It's a also good idea to check the two banks with an infra red gun or a thermometer to see if both thermostats are working correctly, which you can't judge from the gauge alone.

Hello; I responded to this earlier today but it isn't here so I'll do it again. The fans should come on whenever the AC is on or, when the needle is around the "M" position, my experience has shown the gauges are very reliable and quite accurate. The otter switches used by jaguar were made for a multitude of uses and so come in a range of temperatures, On our cars there were at least three different settings. Some cars had the switch close to the thermostat housing which is a comparatively hot location, calling for a switch which operated around 85/90deg. If the switch was on the top tank or the radiator top it would be set to come on at a slightly cooler temp and if it were fitted at the bottom of the radiator then it would need to come on much quicker around the 70 deg mark. You need is a "cold switch, fitting a 95 deg switch at the coolest point will likely render it useless and result in a badly overheated engine. Conversely, fittin a 40 deg switch near the thermostat will ensure that the fans will almost always be on. You can get a good idea of what switch you need by doing some probing. Using some kind of temp probe, check the temperatures at the various locations when the engine is hot, you will be able to see the corresponding tempratures beween the thermostat outlet and the other possible switch locations, this will give you a good idea of what temp switch you need to install, Do not trust the switch you get from any of the suppliers, TEST IT FIRST and see when it operates and that it suits your particular conditions. It might seem like a good idea leaving the fans on permanently but it isn't, (except in emergencies). They are intended to be used about 10% of the time. Having them on 100% will reduce their life span dramatically, it also places a heavy draw on the alternator! One other thought on the V12E cooling system. There are two separate banks and two separate thermostats but only one temp transmitter. Many owners have added another transmitter and gauge to the "B" bank thereby being able to see the temp on both sides of the engine! Good Luck.

Jaguar affectionado and etc.

Al,

If you are using the traditional "otter" switch located at the side of the return hose on the bottom of the radiator, one that I just bought is imprinted "95C". That would turn it on at 95 degrees C, and it's marked off at 83 degrees C.

As Pascal pointed out, you can't go by the position of the needle on the gauge on the dash. Those markings and the behavior of the needle are highly inaccurate, unless they've been varified with an actual temperature reading. First, you should remove your otter switch and check it for correct on/off temps in a pan of water (suspend it, don't place it on the bottom of the pan). Assuming the on/off temps are correct, you can then check the temps of the engine with an infra-red thermometer and compare them with the gauge to see where "normal" really is.

If you feel the otter is turning the fans on too hot, you can either install an adjustable fan control unit (available at most major auto parts stores that sell after-market auxilliary cooling fans) or install a manual switch so you can turn them on when you want. A third alternative (which was done with my car by a PO), is wire the fans to they run all the time when the engine is on. Not necessary, but at least you know they are running. Eventually, I'm going back to the otter alternative, once I get around to installing the one I just bought.

Regards,
Steve Weinstein
'72 E-type 2+2
'70 XKE FHC

Steve Weinstein, JTC-NJ'72 E-type 2+2'70 XKE FHC

al,

it shoudl come in earlier but keep in mind that these gauges are not very accurate. they are good to show you the trend but maybe off in term of exact indication.

check with an IR thrermother, pointed at the Tstat housing. Someone may know the exact values, I ahd once posted them from someone with a similar problem vbut can' t find them...

Pascal Gademer
South Florida Jaguar Club
72 E-type 2+2
00 XKR Coupe
99 XJR