When I got my 95 X300 seven years ago I noticed the fans came on and stayed on when the engine was running. I took it to a good local shop and they replaced the sensor in the bottom of the radiator but the fans still came on and stayed on any time the engine was running. He checked for factory changes and found a mod that jag came up with to cause it to do this. It is a jumper in a connector that is on the right side of the engine compartment near the airconditioner lines. He said they had too much trouble with sensor failing so this was the solution. Removing the jumper causes it to go back on the sensor and the fans stop. I have never run without the jumper so don't know if they would work properly or not.

I have been running this way for seven years and 50K miles. Would like to hear what you guys think.

EZDriver

 

The mod was due to fans blowing fuses during repeated starts. It would probably not hurt to restore it to original, but you can bet Jag went to considerable expense to mod all the cars, so the engineers must believe it is better to run them continuous.

 

As both of you guys are in the States, I wonder was this mod done only for certain markets? Surely running the fans from start in a very cold climate?winter, means the engine will take longer to get up to normal operating temperature, thus affecting MPG?

My fans come on with the ignition also and thought it was maybe the radiator temp sensor that was the culprit, but was happy to leave it be for the summer, not that we get any extraordinary "summers" here in Ireland! Will be looking into it before the cold snap kicks in. If our last two winters are anything to go by, I wont need to delay the warming up process!!

 

Well fuses blow when circuits oveload in any market, so I suspect the mod was for everywhere. And the warm up time is only slightly affected by fans- the cold radiator water is not sent to the engine until the thermostat copens.
The two detriments to running the fans when not needed as I see it is that they might wear out faset and they do load the alternator somewhat, slightly lowering fuel mileage.

 

Yep, we got it here also.

I fitted that relay to mine (found a link somewhere years ago??), so they went back to thermo operation, but are still ON whenever the a/c is on.

One day I will fit a newer style a/c control switch and have them back as was originally designed, and also as the X308 is??.

Yes, premature fan wear is a major factor now, some 15+ years down the track.

 

I am concerned about fan wear. To avoid that I would like to go back to using the thermal switch, but I don't want to blow fuses constantly. If there is a reliable way to implement thermal action I would like to know how to do that.

EZDriver

 

Personally, I don't think the fan wear argument holds any water. My 17 year old 123,000 mile XJR has been wired according to Jaguar's modification, hasn't "worn out" a fan yet.

When not wired for constant low speed operation, as per the modification, it was possible for the temp switching to cause the fans to go from rest to high speed relatively often. That caused current surges that could blow fan fuses and was rough on the fan motors. It was much easier on the fans and fuses when the already spinning fans were kicked up to high speed.

I'm sticking with the mod.

My two cents........

 

OK, OK.

I will go digging and re-read what I read, Aussie English, and Merlot also??.

The way I read it was that the a/c switch failed to switch the fans on to low speed, and waited until "high" was called for, and thus blowing fuses due to the load of "zero to high", BUT, that then left the thermo switch with "no fans to switch" due to blown fuses, and obviously overheated engines followed quite quickly.

Now, the way I rewired (relay actually) the thermo side allows for the thermo switch (lower LH of radiator) to work the fans on "low" and then "high" if needed, and leaves the a/c side as per Jaguar, on whenever the a/c is on.

The fault was deemed to be unreliable a/c pressure switches, and this was a quicky fix that worked.

The X308 obviously sorted the switches etc as they are pressure operated fans, as well as thermo operated. Also, most Aussie cars are wired and operate identical to the original desired way, without ANY issues, and my a/c guy will use a GMH switch on mine one of these days, and put it the way it should be, IN MY OPINION. I will sort the wiring myself, it will not be rocket science, that is for sure.

 

Sorry, I didn't mean to infer that the A/C switch was not the original source of the problem, it was. But apparently the decision to modify the circuit rather than sort out the triple switch issue, was made because certain conditions could cause the off to high speed thing even with a good switch.

Here are the original bulletins.

Cheers,

 

Thanks XJRGuy. That is the info I was looking for. How is it down under. Hot and dry here in East Texas.

EZDriver

 

Thanks Grant for all your effort. This helps to understand the history. Not sure yet what to do if anything. Still thinkn on it.

EZDriver

 

Just to be clear, I agree that there is no reason to consider "undoing" the modification. I only made guess of POSSIBLE arguments for the reverse mod. I am pretty sure that running the fans at low speed rather than it windmilling while off has little or no detrimental effect on their life. In fact, it is possible that keeping the motors powered prevent them from windmilling to an overspeed condition.

 

I took the plunge today and opened the bonnet of the X300. Having found (hahaha) those TSB's, I needed to know what I had.

Mine is after the vin #s listed, and is a 12/95 build car, AND, has only 1 switch on the a/c pipe (4 wires), and NEVER had the single switch that is discussed, no provision on the pipe for said switch, AND, had the bridge loop from the factory. From what I read that single switch port on the pipe was deleted at a specific Vin # and the bridge fitted.

I have fitted a relay in lieu of the bridge, (read that bridge mod somewhere 2 years ago), and the fans now work on thermo, on LOW, and HIGH, if required. The fans are still ON whenever the a/c is ON, and I am happy to leave it as that.