Power for the clutch relay comes from the ECU OR the fuel temp switch. So if the fuel temp gets hot, it will turn on the AC to cool the fuel, even if the climate control is not calling for cool. It then grounds through the pressure switch, so the pressure switch has to be closed by freon pressure in order for the clutch to engage, that's your compressor protection.

That ebay compressor is the later Sanden style that was used on the 6.0 cars. Not sure it if can be retrofitted to a 5.3, but the original A6 is quite a bit longer and the style of hoses is different.

 

Thank you Jag B.... Interesting... Possible all of my probs (well, not all, lol) might be hinging on the wiring with the fuel temp switch...? Is that possible?
Looking at the elec diagram its pretty clear that what flows thru that switch is directly form the ECU and dash control on its way to the relay. Straight shot almost...
I have to say,,, I feel like and *** for missing it,,, BUT am very encouraged (I wish I wasn't at work right now) to go home and see what I can figure out with the wiring to the fuel temp switch.

 

Don't worry about the fuel temp switch. High fuel temp can engage the compressor, or the climate control. They act independently. If there is no pressure in the system, neither will cause the compressor to come on That wire from the pressure switch can br fragile, make sure it's is electrically sound. I have also run across a situation where I changed a pressure switch and it wasn't making electrical contact with the backing plate. a bit of a push to make sure it was seated and things worked.

 

Got ya... I'll be checking it out in less than 2hrs...

 

Actually... Take a look at the elec diagram. The first "stop" from the dash control,,, is the fuel temp switch. I don't see anything between the FTSwitch and the relay...

 

There are two feeds into the coil side of the relay, both Green/brown. One from the fuel temp switch, the other from the climate control ECU. Either of them can provide power to close the relay.

 

Hmm. What I have, or think I have, is the green and brown, and black and purple going into the switch on the side of the fuel rail in the engine bay. I had dangone wrong wires connected, for a good while rhere... Don't know what those go to now. The wires that were flopping around without a home since forever are the ones that go to the fuel temp switch. If you look at the diagram it looks like the black and purple go into the switch and the green and brown come out. That's what I have but still, I'm confused.

Anyways, at the climate control ECU I have about 1.17v in the green and brown... And between 3.0v and 5.1v coming from the knob on the black and purple - changing as I turn the knob. I can hear changes In the climate conteol housing as I turn the knob and the voltage fluctuates... In turning the knob on the dash control the Black and Purple changes but not the Green and Brown.

In the engine bay I get about 3v at the switch from the black and purple and just over 1v on the black and green. HEEEELP... lol

I saw a seal kit for the A6 on eBay. Just 8 bucks and looks like something I could do. More my cup O tea... What do y'all suggest. My worry is a no fix and being taught my lesson by wasting another bunch O money in r12...

What say you?

 

No thoughts from anyone on my last message/addition here????

Update... I had the ECU out the other day, opened it, inspected the board and nothing looked cooked. Which doesn't tell all Or much.

I removed 5 tiny 5 or 6 mm nutts and cleaned the connection to the steel plate that looks like the common ground for the entire ECU unit with a dremmel. Results were shiny clean connections. Plugged it back in, no change. Removed the section of wire that was damaged by what appears to have been a small fire from the previous owner and cut the wires back to about 1-2 feet from entrance to the fire wall. The wires before and after that damaged area look and feel like new,,, they were sleeved and tied to other looms. Plugged ECU back in, tried for the readings, no change. About 5.1-5.2v volts max from the black and purple,,, about 1.17 - 1.18v from the green and brown at both the ECU outs and at the wires exiting the fire wall.

I hate the idea of buying an ECU but I can't see what else it might be.

And,,,, Jenson A.C. says they have A6 quality rebuilt/reman compressors. They seem to be a good outfit that do LOTS of a.c. work,,,, re-manufacturing lots of compressors for many kinds of cars. They offer pics of their shop and set up. I just can't figure out how to get the 12v I'll need to engage the A.C. relay to send the voltage to the compressor. At a loss here.





anyways,,, finally found my LHdrivers side sill/tread plate and installed it today. Looks good. Came a long way to rest where it is... In my XJS. Still can't believe I own her sometimes. ☺😁

 

Hello All...

Any suggestions on how I can reliably get 12volts to that compressor? Or, where it might be that I am losing the 12v? Completely stuck here...

 

For instance - where can I find the "G12" common ground point for all of the items grounded there? I think finding that would matter. As would the "CP7" in the diagram. What is a CP7?

Lower and Upper feedback POTS and Temp demand POTS are all grounded at G12. Where are the actual POTs? Are they the ones (the POTs) IN the controls on the dash?

AND,,, what might the "Temp Diff POT" (center left of image) have to do with chasing this problem,,, if anything? Will voltage to the GN wire increase as these POTs are rotated/engaged?

Also,,, which pin outs on the ECU should or would be involved in getting that 12 volts via GN (pin 20) to the relay and compressor?

Wits end with this...

 

Hello all.

****EDIT and CORRECTION**** Everywhere below where I mention Brown and Green (NG) wire,,, it is really Green and Brown (GN)... Mostly green with a brown stripe....

I've ordered a reseal kit for the A6 GM compressor. $20. I figure if I cannot get it right I can order a new one for $180. 20 bucks, if it works, is worth the risk I figure.

So, no matter what, getting all the wiring I can get right, right, I only get 1.20v from both the Climate Control signals to the relay. It's a Brown and Green NG wire from the ECU... And a Black and Purple BP wire from the control knob (see schematic for convertible in previous post)... Its not enough to activate the relay... To the best of my understanding, everything else is where it is supposed to be and seems to function including the Idle Relay and SAV when the relay is engaged manually...

I have 13.60 (+ or - a few tenths volts) at the load end going in to the relay. Position 30 I believe. If I activate it (manually) it sends voltage to the SAV and the Idle Relay as it is supposed to,,, and the compressor. Only IF I manually activate it.

What I intend to do - There is a 12+ volt power wire, white, that is hot in positions 2 and 3 with the ignition switch (key). This white wire runs thru many components within the car. I do find that 12+V feed running exactly in the area of the starter and A.C. relays in the RH corner under hood. I intend to tie into that line and run wire into the cabin, rig a toggle switch, and run it back up and out to the relay control end... I intend to remove the brown and green NG wire from the relay entirely and plug into the control side using the old NG plug, thus supplying the juice necessary to fire the control and provide 12volts (as usual) everywhere it is supposed to be. Also putting use to the diode that is in line with the old NG wire. On the control side, I don't want to dumping 12+V back into the Climate Control ECU, I will leave that NG wire AND the Black and Purple BP wire dead ends. Not using the fuel temp switch on the rail.

From what I can see the Brown and Green coming from slot 20 at the ECU and the Black and Purple coming from the temp control knob are pretty much dedicated to the a.c. relay control. They both seem to have a cross point at the fuel temp switch on the rail, but work with little else...

Any thoughts, opinions, warnings or suggestions SUPER welcome. Sorry for typos,,, typing on my phone.

 

So this thread took some turns and I think got a little lost in the sauce,,, but for those that care I think that I have solved my A.C. problem. I would have preferred to have things working directly from the climate control ECU,,, OEM,,, but hey. What can ya do...?

Nothing was working to get enough voltage to the a.c. compressor relay from the ECU, so I just tapped into the ignition 2, 3 postion 12v wire that is readily found in several place around the vehicle. I used that for the control side of the relay and ran a toggle switch that I will mount once I reupulster the inside this fall. With that 12v to the control side of the relay, everything in the system that was supposed to be activated,,, less the fuel rail temp sensor,,, came on line.

I resealed the A6 compressor a couple days ago and set it in the car. It held 30+ negative pounds of pressure for two days and this morning I pumped in some r12. Low and behold,,, center vent pushing out air at 40 41 degrees... SAC kicking on nicely when she is in gear. Flaps and recirculation working, leg vents, defrost, center and side vents working,,, drips from drain running under the car. I had to give some attention to the drains. Both were clogged in the unit,,, and one of the hoses that goes into the transmission tunnel was burned/melted shut... The Idle is a little rougher than I would like, but it was before.

I got put out of work and was running lowER on doe $$$ than usual which is why this took so long. Couldn't buy the bits I needed at the end.

Now,,, OFF to the cruise control challenge. Tested actuators today and both work and hold a vacuum. Funny things going on with my speedo,,, trip computer,,, and the console switch was toast when I took her home. QUESTION --- Is the console cruise control switch the same as an everyday XJS window switch? Does it hold in the OFF,,, ON and SET positions or does it end up in the "center" postion when not being depressed...? Looks like I have some things to figure out...

I want to say thanks to you all for ALLLLLLL the help, insights, attention, advise,,, AND... Getting closer.

oh and,,, made a good friend who is an auto painter... he is excited to do a final paint job on cherrypie AND is going to work with me in all of the prep work right in front of my place. Good stuff

Was feeling in over my head. Never been there/here before. Ended up being fairly easy...


see you all on the flip side. I guess I'll start a new thread...

 

JJJ
The console switch for the CC is not the same as the window switch on my car, which is a Delanaire Mk II. I doubt your Mk III is the same either. You can pick them up from breakers easily enough in the UK, and there may be the odd new one about. Congrats on the A/C working, good for you!
Greg

 

Good morning.

Thank you... It took a while but,,, although it's a workaround fix for the ECU problems,,, so far I am very pleased with the result. Very much... I'll keep an eye out for leaks or something going wrong but so far so good. Last night i went out for a drive,,, had the A.C.compressor running but with out the blowers on. When I did turn on the blowers,,, frosty (literally frosty) air blew out of the vents. It was a good thing. Ait temp out of the vents as low a 37degrees

After I posted the questions about the CC switch, I realised that it was a dumb one! I'll have to start looking around to source a proper switch. I want to start working on and troubleshooting the CC right away. I started a thread last night about it. Have something to add now.

Thanks all. See ya on the forum!

For my troubles... AC leak dye!!! PITA.

 

Looks like I spoke toooo soon... Must have a leak, somewhere... The chase continues! Thought I needed to & had better tell on myself, lol... smh...damn it!

 

So I'm back at this. Just got the Jensen unit and wondering what, if anything, folks have done with the RH connection high side connection and if there is a known flexible hose that can be used to replace the rigid steel tubing?

Due to the shorter overall design of the Jensen vs A6 compressor the difference pushes the rigid tubing right into the fill pipe at the top of the Rad cross pipe...then, I don't think it's a good fit in other ways.

Any suggestions are greatly appreciated.

Is the connection type for the OE (with Oring seal) a common connection type? Wondering if I can just go to the big box auto parts store and find something flexible that will fit.

 

Go to an aircon specialist, they will make you up a hose that will go on the end of the piece in the photo, to join it to the condenser hard line, or, make you up an entire new flexible piece to go from the compressor to the solid line into the condenser.

 

That's what I'll do. Thanks!

​​​Took off the entire length of hose and rigid tubing between the condenser and the appliance and am headed out now to see what I can find. Should be fun, lol

 

Quick question... That barrel in the black rigid tubing in the photo. Is that required/necessary? Can my replacement section eliminate the barrel?

 

It's a muffler/pulsation damper. Nearly all AC systems have one, so you'll probably need a different one. That's a Sanden style compressor, there should be a muffler out there that fits it.