Project: 4.8 LR4 (LS) into '98 Jaguar XJ8

[Hotwire]

What's the A/C update?

[HectorM52]

REVISED LIST - AGAIN!!


Done:
Tighten crossmember bolts
Install grille
Install hood
Get exhaust
Install driver's door panel
Tighten up tranny cooler lines
Replace reverse-sensor on shifter
Replace PS pump to get rid of leak - newly completed
Pressure wash engine - newly completed

Need to do to finish this damn car:
Troubleshoot shifter lock issue
Pick up & install ALDL connector
Get A/C working
Wire loom
Heater line plug
Fix oil leak
And the general one: Troubleshoot any other issues found!!!

[HectorM52]

The update is that I still don't know why this damn thing isn't working...

There are currently two questions I need to answer for myself:

1) Is the A/C not kicking on because I removed the converter module from the system? This is the module we bought that makes the GM PCM talk to the Jag CAN/BUS system. It was not working properly so I mailed it back to California to the supplier and hopefully he'll turn it around this week. I am wondering if the CAN/BUS system is not allowing the A/C signal to be output from the A/C control module because it's not seeing any engine or tranny in the system.

To answer this question I need to have the module back, plugged in, and working correctly.


2) Or is it that I have stolen the signal going to the A/C control module therefore it's no longer giving the "turn on" signal to the GM PCM? Basically, I have been trying to find a high-pressure switch that mimic'ed the GM high-pressure sensor that's normally in the back of the Silverado compressor. As you know, I'm not using the Silverado compressor, I am using the GTO compressor - WITH A SILVERADO PCM. So I need a high pressure switch that is closed as it sits installed...then opens when the pressure gets too high. The ones I am finding are normally open that close upon high pressure.

So I was going to steal the Jag sensor because it is a switch with THREE outputs, one of which works like the Silverado switch. But the problem is that when I stole that signal, I stole it from the Jaguar A/C control module!!!! So I don't know if the Jag control module still wants to see that pressure switch or not...but I'm beginning to think it does. Because it is not giving the "turn-on" signal to the GM PCM...

To answer this question, I need to replace the Jag sensor and let it do what it was doing before, then just jump the other connectors off. That just takes time. Maybe tonight.

Holy crap...what a convoluted mess.

[HectorM52]

Originally Posted by HectorM52

There are currently two questions I need to answer for myself:

1) No, not this one.

2) Or is it that I have stolen the signal going to the A/C control module therefore it's no longer giving the "turn on" signal to the GM PCM? Basically, I have been trying to find a high-pressure switch that mimic'ed the GM high-pressure sensor that's normally in the back of the Silverado compressor. As you know, I'm not using the Silverado compressor, I am using the GTO compressor - WITH A SILVERADO PCM. So I need a high pressure switch that is closed as it sits installed...then opens when the pressure gets too high. The ones I am finding are normally open that close upon high pressure.

So I was going to steal the Jag sensor because it is a switch with THREE outputs, one of which works like the Silverado switch. But the problem is that when I stole that signal, I stole it from the Jaguar A/C control module!!!! So I don't know if the Jag control module still wants to see that pressure switch or not...but I'm beginning to think it does. Because it is not giving the "turn-on" signal to the GM PCM...

To answer this question, I need to replace the Jag sensor and let it do what it was doing before, then just jump the other connectors off. That just takes time. Maybe tonight.

No, definitely tonight! And, man, that guy up there is smart!

Since I don't have the module back, it was tough for me to test my theory #1. So I went with theory #2. I temporarily hooked up the Jag high pressure switch the way it was before I stole the wires for it. Then I jumped the high-pressure circuit. Unhooked the battery for a "hard reset" of the Jag CAN/BUS system. Started the car, hit the A/C, and VIOLA, I hear the A/C click.

So I learned two things. 1) The Jag needs that sensor/switch in order to send the "turn-on" signal from the A/C control module. I tested this theory by unplugging the switch while it was running. It cut off. So that theory was confirmed. And 2) I still need to find a high-pressure sensor that suits my needs. AKA normally-closed high-pressure switch that mounts on a schrader valve.

So I'm off to find that switch. Any help is appreciated.

[Hotwire]

If the jag is controlling the ac, then don't worry about the silverado switches..

All you'd need to do is send 12v to the pcm pin 17 so it knows to kick the fans on.. right?

[HectorM52]

Ummmm...

Are you saying I should be using the jag switch ONLY? Because it has both the high and low switch within that one leg? But I thought the low pressure switch needed to be located in a different line altogether?

Furthermore...the Silverado PCM cannot control the fans without more work being done (internal programming). Which I don't have access to.

So based upon that logic, I'd not need ANY A/C-related feeds going to the Silverado PCM...

[6SpeedBlazer]

You do need ac feeds going to the silvy pcm. Without the pcm "seeing" an ac request you wont get an idle bump.

[HectorM52]

Ahh, yes, good point.

I guess I'll research whether or not I can just run the "on" wire from the Jag into the Silvy PCM. Then maybe just hook up the recirc-switch to the Silvy PCM too. Then have the Jag take care of the high and low pressure cutoff's.


Anyone ever heard of a switch having certain pressures at which it cuts on - which in turn cuts on the electric fans? The way the Jag switch is built, it has three ranges.

1 normally open switch that closes at @ 174 psi
1 normally open switch that closes at @ 290 psi
1 binary switch that is closed between 29 and 435 psi, but is open below and above that, respecitively.

That switch makes me wonder if it was telling the Jag PCM to turn on the low-speed fan at 174 psi and turn on the high-speed fan at 290 psi...

Someone help confirm or deny that theory!!!

[HectorM52]

Hotwire!!

Tell me what I need to go get tomorrow from Radio Shack...what are those resistors? I need two...

I'm going to "only" run the fan based upon coolant temp and refrigerant pressure as described above.

So I am going to put them in line from the back side of the Jag trinary switch between there and the low-speed fan relay and the high-sped fan relay.

I honestly think that this is the best way to do this. And this closely mimics what the Jag had from the factory.

[Hotwire]

what resistors are you talking about?