Spent $500 on ac that runs sometimes
ac guy said to take it to an auto electrician after finding p1460 wide open throttle fault.
Found computer is not providing the ground switching signal to turn compressor magnetic clutch relay.
auto electricians said it had to be sent to specialists ( $500 for nothing!) Then they trll me the "specialists" dont "do jags"!
Anyway of bypassing this with a switch of some sort?
Thanks
Peter

 

Details of P1460 are here, page 48:

http://www.jagrepair.com/images/Auto...os/PE20001.PDF


Under "Possible Causes" in the far right column, it has 5 possibilities listed, not just a lack of ground from the PCM. Are you positive the mechanic confirmed a lack of ground from the PCM to energize the clutch control relay? Or was he just reading a generic definition from his scanner?

You could quickly run through the last 4 possibilities listed and it won't cost anything but a little bit of your time. Wiring diagrams are here, see fig 03.2 for the AC compressor clutch control relay:

http://www.jagrepair.com/images/Auto...x2022001en.pdf


Please see this guide for details of how to test the relay by substituting a known good one, in post #5:

https://www.jaguarforums.com/forum/s...ol-how-185002/


The same section also has details of how to check the resistance and amp draw of the compressor clutch coil. The initial steps are all done from the front power distribution box, so this also tests the associated wiring.

Also, please run the test of the DCCV as detailed in post #2 of the same guide. You may think it wouldn't matter, but if the DCCV is drawing too much current (but not enough to blow the fuse), this can reduce the voltage reaching the compressor clutch. This in turn would reduce the clamping force at the clutch and cause slippage. Low voltage at the relay might be misinterpreted by the PCM as a wiring problem, and flag the P1460 code. I'm not positive about this, but checking the DCCV operation is easy enough and should help rule out this possibility.

And to answer your question about rigging up a bypass switch, that won't work. The PCM has to be able to cycle the compressor clutch on and off as it sees fit. You can't just leave it running all the time. I don't know if this would cause any actual damage, but the evaporator would get too cold and ice over on the outside. Strange as it may sound, too much ice is not good. It restricts airflow and heat transfer, resulting in limited cooling. The evaporator has to operate just above freezing for best results. More cold is not better.

 

+1 on running the diagnostics as described above.

What other DTCs are stored in the system?

What is the voltage across the battery terminals with the ignition in the OFF position when checked with a voltmeter?

 

I just took a second look at Jaguar's list of fault codes, linked above in an earlier message. I missed it on the first look, but Jaguar doesn't even call this a "wide open throttle fault". That must be a generic definition.

For P1460, Jaguar calls their version of the code an "A/C compressor cut-out malfunction". For convenience, here are the 5 conditions Jaguar says can set this code:

PCM to A/C compressor clutch relay circuit: open circuit, short circuit
A/C compressor clutch relay to A/C compressor circuit: open circuit, short circuit
A/C compressor clutch relay failure
A/C compressor clutch ground circuit: open circuit
A/C compressor clutch failure


If I were a gambling man, I'd say the most likely culprit is the relay and start there. As previously mentioned, you can swap in a known-good relay and see what happens.

 

There's no generic meaning for any P1 code. You always need to look them up by make, model and year.

 

I did not know that. I'll have to add that to the list of things I didn't know. It's a very short list, so this will be #2, right after "Where do babies come.from".

All seriousness aside, this is a very interesting problem. I've been doing some mental gymnastics, trying to figure out what criteria the PCM uses to set this code.

No response yet from the OP. Hope this wasn't a drive-by.

 

A weird maker could even define each P1 code differently for each car off the production line.

I don't think any maker ever would, though! (Think of the pain/cost of the OE diagnostic software.)

 

Thanks for your help. Have printed electrical manual.
Still trying to work out repling to threads.
Peter

 

You're doing OK it seems!