Whilst troubleshooting the slow leak the A/C system had developed
over the past 3 years, I finally found the culprit this week.

I had just gotten the A/C pressure up and the compressor clutch
was engaged full time when it started "stuttering/chattering", switching on/off rapidly.
I was in the drivers seat and varying the engine speed when the "stuttering" happened.
I also saw steam coming off of the exhaust manifold (?). I thought I had
a ruptured high pressure line.
Instead the A/C pressure sensor/switch was leaking r-134a out the top of the solenoid body.
The high pressure side was showing some fluctuations during the charging
process. But nothing major to indicate a bad fitting or hose.
I used a leak detector fluid that didn't show anything until it started
spraying out the top of the switch/solenoid body.

I have a replacement switch DBC11279 on order.
Retail - $215.00 (US)
Got it for $185.00 (US).

I see some references to the DBC11279 switch being used on the 1994 -1998 XJ6 models. But, the pictures I pull up show a switch/sensor
slightly different than the DBC11279 unit used on the 1994 XJS.
I did go to a salvage yard to get a XJ6 version. Close, but no cookie.
Couldn't use it.
The yard had a 1995 Vanden Plas XJ6 on the stands for pillaging.
Sad to see such beauty being wasted.

By the way, go to SAM's Club and get the tank of 30lb R-134a.
It is about $70.00+ there.
If you gotta use 12oz cans they got a 12 can package for $38.00+.

Way cheaper to use than those 12oz cans being sold for $8 -$16 each
at the local convenience stores and auto stores
I have 6 vehicles that require occasional re-fills along with my kids
rides.
More on the refill process when the switch/sensor arrives!

Bob Scarborough
P O R - Press On Regardless

 

The new sensor arrived via UPS in a box that was "slightly" deformed -



smushie ?

The sensor was not damaged and was ready to install.
The A/C system on the 1994 XJS does not have Schraeder (?) valves
on the High pressure sensor attachment point like the XJ6 autos.

The A/C system has to be purged and at 0 psi for the sensor install.

First to locate the sensor.
It is on the exhaust side of the engine in the engine bay down on
the chassis rail. Way down on top of the chassis rail.



It's down there under the hose.


The sensor requires a 17mm open end wrench to remove the sensor.


17mm open end wrench to remove sensor

Careful when removing the sensor, because the sensor opening
has no protection from dirt and crud falling into the pipe.


Sensor mounting point

Once the sensor is installed use the normal A/C recharge process.
I use my vacuum pump and pull a vacuum and let it sit for about 4 hours to see if everything is leak-proof.



Nice Vacuum and ready to receive r134a.

The whole system got recharged after the sensor replacement and
2 days later the system was still charged. Before the sensor
replacement the charge would leak out in a day.

Now my wife's XJS is a really cool ride !

 

Bob,
I need to replace the pressure switch on my '95 4.0 as well. Is there a check valve in the receiving female connection?
Thanks,
Jerry

 

Jerry,

As that thread is 9 years old, and also Bob hasn't posted for the last 4 years, you might want to start a new thread and look to others for an answer.

Good luck

Paul