I've been trying to diagnose an intermittent issue with my AC. It seems to work well when temps are low but doesn't work as temps rise above 80F/27C. I had gauges on it and noticed the High side rising above 300 psi and then the electric fans kicked in on Fast speed for a few seconds and the pressure dropped. After additional research here I took a look at the fans again this morning and neither fan was on in low speed with the AC on. It sounds like a faulty pressure switch. The one I see is near the firewall and is 4 wire switch, part number LNA7657. I'm thinking this may be the culprit.
I did see something from a PDF I downloaded here "An official modification was to permanently connect together the wires that originally went to the single-pressure switch (which was mounted on the a/c pipes next to the offside bulkhead). This is the bullet connector in the second photo and means that the radiator fans should run at low speed all the time the ignition is on in order to keep the air conditioning radiator (in front of the car radiator) cool. If the radiator temperature exceeds 100°C then both fans should run at full speed." The photo was too small for me to make out what was done. Is this an earlier version of the switch I have maybe?

 

Further investigation: The 4 wire switch I thought might be the problem isn't. One set of contacts is NC and will open to turn off compressor and the other is NO and closes to run fans in High Speed, which I verified was working the other day. So my problem is no low speed fans. I assume this is from another switch or the fan control relay module?

 

There is a TSB which in the end the fans will be on low at intial cold enginne starting

The 2 wire low ( working ) pressure switch is the low fans command and the other nearest firewall 4 wire is the high ( working ) pressure switch for high fans command

The 4 wire is also the underpressure and overpressure compressor cutoff

The 2 wire low pressure switch is removed and not used after TSB done and a jumper plug is installed on 2 wire connector , you can leave your low pressure switch in place unless leaking

True the engine coolant temp switch as the 3 wire switch on the rear car's left lower radiator comes into play as a second command source and the heart of the fans control is the Fans Control Module ( a 3 relay package as 1 unit ) located just Fwd of the ca's front left tire from the car's underside

My Fans Control Module was mounted upside down letting in water to ruin relay power contacts ( connector should be down and you could shake mine hearing water rattling around inside )

A black colored FCM on the V - 8 X308 does not work for the white FCM on the X300

There is a simple test of the Fans Control Module coming up

With a paper clip on the 3 wire coolant temp switch between the white wire and the black ground you will have low fans mode , remove clip and install on the other white wire and the same black ground wire and will have high mode ( a low current portian of the fans circuit )

Ask questions

Off to dialysis chair for hours

 

Some related TSBs

 

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Thanks for the info. Did the Fan Control Module test you outlined and still only fast fans. I'll have to seek out the coolant temp switch.

 

[img alt="I assume this is the relay module.
"]https://cimg8.ibsrv.net/gimg/www.jaguarforums.com-vbulletin/2000x1504/img_5013_b3fd616287184acf4b7eb9cc676a806b23bc2193. jpeg[/img]
I assume this is the relay module. The jumper test confirms this is the problem, correct? This would rule out the 2 wire refrigerant switch?

 

In the end you would remove the 2 wire pressure switch and jumper or splice the 2 lone wires

The test only confirms the fan motors and the FCM and not the 3 wire temp switch on the rear left radiator and not the freon pressure switces ( both )

Will look at your part # above as there a 2 part #s on the X300 both white in color and not simular black on the X308

Be careful if removing the fans motor connectors lock tab as can be brittle from age and break off if levered out too far

The right fan motor connector can be brought over to the left but not vice versa

Watch your hands and loose wire going into fans

 

I'm still not sure where the 2-wire pressure switch is located. Is is possible that a '97 does not have this switch? I thought I remember reading a thread that some models only have one switch. Thanks

 

Could be

on same line fwd of the 4 wire pressure switch

 

I figured it out. It was right in front of my face. Indeed later models deleted the switch. The white connector was for the two wire switch and it just has the jumper wire on it . I bought the relay module ebay and hopefully that will fix that problem. With no slow speed fans I would assume the AC would not work very well when temps get higher. I still may have an overcharge but I'll see how it operates after I swap the fan relay module.

 

I missed this post. It would have saved me some time searching for the switch that didn't exist on my car. My car already had the mod installed and the switch was never there. But thanks for the info.