XJ6 & XJ12 Series I, II & III 1968-1992

AC Diagnosis and Questions

 
  #1  
Old 05-26-2019, 12:06 PM
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Default AC Diagnosis and Questions

It is getting hot in Phoenix and I'd like to get my AC working.

I bought this car in September of last year and the AC didn't work on the test drive - just blew hot air out the demisters. The woman I bought it from said it'd worked fine and they needed to charge it every couple of years.

To drive it through the winter in Phoenix, I wired the heater valve closed to keep from roasting all the time, but now I want to have AC.

Here's what I know so far (It is a '84 XJ6 S3 Base car -60K mi- I have a Mityvac and a vacuum gauge)

- There's little or no freon in the system. I assume I can diagnose the air distribution system divorced from the refrigerant system.
- I can hear the servo move and see the connecting rods actuate when I move the controls
- If I just turn the temperature selector I can hear the motor in the servo too
- Blowers seem to work fine
- The center vent never moves/opens with any position of the controls - air comes out of the cheek vents and defroster vents.
- There's no vacuum signal to the water heater valve in any control position
- There's a good vacuum signal coming off the engine, and when I took the check valve off there was clearly vacuum going into the car with no leaks (vacuum released when I pulled the hose)
- The firewall check valve is working, has no leaks or obstructions. Reservoir and all the vacuum lines in the engine bay held 20" of vacuum overnight.
-Everything under the cheek panels looks pristine and unmolested, and all the rubber hose is supple. There is, however, some corrosion around one of the flap shafts that protrude through the airbox on the passenger side. The linkage could easily be moved by hand.

My conclusion after the first diagnostic session was that there wasn't any vacuum getting to the airbox in the passenger compartment and I wondered if the vacuum solenoid was functional. I looked for a white PVC hose and found it but I can't find anything that looks like the vacuum solenoid.

My next step would be to hook up a vacuum source to the PVC lines to the actuators and see if the center vent moves, but I suspect that since the heater isn't seeing any signal, that lack of vacuum to power it is the problem not the actuator itself.

My questions.......

-Where should I find the vacuum solenoid?
-
-Is the power to the solenoid fused somewhere?
- I'd like to expose what's under the ski slope and the side panels to look for the vac solenoid. How do i get the side panels to the ski slope off?

Any suggestions on where to go next to get all my vents operating correctly would be appreciated.
 
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Old 05-26-2019, 03:16 PM
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there is a small vacuum solenoid towards the rear of the driver's side floor or "knee" heater vent. It has two black rubber elbows connecting to it as well as electrical wires. Those rarely need replacing.

are you planning on using R12 or R134 refrigerant? Do you know what refrigerant was in the system previously? Have it tested before using any refrigerant.

also R134 requires barrier hoses.

There is a business called Retro Air in Houston run by Rock Browning who could help with getting it fixed. He also sells an improved GM Harrison compressor if yours is bad.

also if the amplifier has not been replaced, there is a guy called Gary which sells a replacement amplifier and he can help you diagnose too.
 

Last edited by Jose; 05-26-2019 at 03:23 PM.
  #3  
Old 05-26-2019, 08:48 PM
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Yes, Gary is very knowledgeable and is the owner of Jag-aire
 
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Old 05-27-2019, 11:31 AM
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At the risk of starting the Refrigerant discussion all over again, a Third Alternative is HC-12a.
Wholesale Refrigerant - Cheap R22 Freon, R22a, R410a, R12a, R134a Replacement

I can speak from Personal Experience, This Stuff WORKS GREAT! It's easy to use and leaks down Far Less than even R-12. No barrier hoses are required, nor any other change to Original Equipment such as compressor, condenser, or expansion valves.
(';')
 

Last edited by LnrB; 05-27-2019 at 11:39 AM.
  #5  
Old 05-27-2019, 12:59 PM
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On the refrigerant issue - I have enough old stock R12 squirrelled away for one recharge. The neighbor picks cans up at garage sales since they stopped selling retail, keeps a running tally of his average cost, and he'll sell me as much as I want for $10 a pound.

The plan is to pressure check the system and see if it will hold pressure. If it does I'll charge it with R12. If it doesn't I'll fix what's needed, flush it and convert to R134

Now on to what I think is the crux of the problem............

I mentioned that I'd observed some corrosion on the evaporator case. Following the water/corrosion trail down the airbox, it looks like condensate has dripped into the servo. There's quite a lot of a powdery substance at the bottom of the servo. Looks like water fouled the vac switches that control the center vent. (pulled a vacuum on the line and the center vent worked properly)

How does the servo come out? There's a single push fastener on the plastic cover and one acorn nut in the duct. Are there other fasteners?

I found the vacuum solenoid valve when I took off the stub duct that feeds the cheek vent on the driver's side. I put a VOM between the pink lead and ground and turned on the ignition and turned the mode selector to 'high'.

When I did, a moment later the fans stopped working. (I did get a voltage reading to the vac solenoid) The fan fuse is fine, but there's a fuse on a brown wire on the passenger side that's blown. It had a 10A Buss fuse in it instead of a Lucas, so someone has been in there before and replaced it. Does anyone know the function of this fuse and what the proper amp rating is?
 
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Old 05-29-2019, 07:44 AM
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Yes, that is the RANCOR tempurature 10amp fuse that connected to the A/C clutch. It's supposed to be a 10amp LUCAS fuse. Apparently LUCAS fuses are a bit different from regular glass tube fuses in that that have both a rating in continuous and overcurrent. There are posts in this forum that explain it better than I can. Also they seem to be a few MM shorter and fit in the in-line snap together fuse holders better.
 
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Old 05-29-2019, 10:18 PM
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Thanks Bill - that is useful info and explains why when I replaced the blown fuse, no functionality was restored.

It looks like I have three issues-

1) The RANCO fuse is blown and the system is empty - the AC was inop when I bought the car and the fuse likely blew when the PO had the car.
2) There's no vacuum getting to the hot water valve or the center vent in the cabin. All the air comes out the defrost vents. There's evidence of condensation having dripped onto the servo mechanism and I'm thinking the vacuum switches are not functioning because they were fouled with water. There's no vacuum leaks on the engine side of the firewall.
3) Fan stopped working when I'd measured voltage at the pink wire to the vacuum solenoid while turning the temp selector and mode selector to see if there was a electrical signal to the vacuum. All the fuses check ok, so will move on to the fan relay and the mode switch. Fan relay first because it is easiest to get to

My next step is to check the fan relay to see if that is functioning properly.

Any suggestions are encouraged.

Phil
 
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Old 05-30-2019, 04:12 AM
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@ LnR; The manufacturer of "Frosty Cool" HC12a states "FrostyCool 12a Replacement Refrigerant requires approximately 1/3 the amount of the original charge in the system and must be charged as a liquid".
How did you achieve that?
From what I know, when charging as a Liquid, the high side of the compressor is used , with the system 'off'.
Was there a work around? or did you have a shop do it?
 
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Old 05-30-2019, 09:42 AM
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No shop, did it right here in my garage.

With system Evacuated, engine Not running as stated in instructions, simply hold the can(s) upside down. Run it into the High side and from then on, just followed the directions and pressure recommendations.
(';')
 
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Old 05-30-2019, 09:56 AM
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yes, can upside down dispenses Liquid refrigerant.

normal side up dispenses gas refrigerant
 
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Old 05-30-2019, 11:10 PM
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Well, I'm never going to make it as a bulb-snatcher - it's true confession time.

I put my HF meter on ohms and checked all the AC fuses insitu - the meter beeped indicating continuity in all the fuses.

Today I had the test light out and thought I'd check one more time, and I'll be darned if the light would not come on for the #13 fuse. I replaced it and all my blower functionality came back!

So now I'm back where I was a couple days ago diagnosing the always defrost and no center vent condition.

The servo has evidence of condensate water on the vacuum valves and they were very sticky. I managed to get the servo out of the car and the vacuum valves out of the servo to spray a little WD40 in them and exercise the shaft.

The servo is reassembled with the cleaned up valves and I'd Iike to be able to energize the servo to check them. Any suggestions or precautions would be welcome. My plan was to run the servo and check the valves and microswitches operation before reinstalling it.

Row52.com says there's a couple of XJSs in a local self serve junkyard that should have the Delanair 2 system in them. I'm going tomorrow to clip the connectors off of the harness to use as a breakout tester for the mode switch, servo and amplifier. I'll get the servo too in the hope that it is better than mine, but I should still be able to salvage parts off of it if it isn't. I'll leave the mode switch, but I can always go back and get it if the diagnosis shows it is faulty.

More questions coming.................
 
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Old 05-31-2019, 12:29 PM
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Is a blown fuse to the RANCO likely to have happened when the system ran low on Freon?
 
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Old 05-31-2019, 02:39 PM
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Found Gary Crosby's/Jag-Aire.com instructions on how to power-up the servo out of the car so I've checked the operation of the vacuum valves after I cleaned, lubed and reinstalled them - seems to work ok.

Before I reinstall the servo I want to check the rest of the vacuum system. To help keep my head screwed on straight, I wrote a test plan - comments solicited-

Vacuum System Diagnostic Plan

Reference “Jaguar XJ6 Vacuum System” plumbing diagram posted in the reference section of this website

Servo Vacuum Valves
  • Engine off, ignition off
  • Servo out of car and on bench (could do this in the car too, but my vac valves were sticky from condensate dripping on them so I took the servo out to clean them)
  • Vacuum source to heater vacuum switch
  • Vacuum gauge to actuator side of the vacuum switch
  • Apply vacuum
  • Apply 9VDC from battery to red and purple pins on connector – see instructions for this on Jag-Aire’s website.
  • Reverse polarity on battery and run the servo between the limits and verify vacuum switch is working
  • Repeat for vacuum switch for center vent
Vacuum Supply to Cabin and Defroster/Lower Heater Flap
  • Engine off, ignition off
  • Connect vacuum source to hose coming off intake manifold on engine
  • Plug hose supplying vacuum to the servo (and just the servo) on the passenger side of the airbox
  • Mode selector switch to ‘off’
  • Verify system holds vacuum
  • Turn mode selector switch to ‘Defrost’
  • Verify that both left and right defroster flaps moved
  • Verify that the system holds vacuu
Face Level Vent – Plumbing and Actuator
  • Engine off, ignition off
  • Connect vacuum source to PVC tube at servo
  • Verify center vent opens and holds vacu
Heater Water Valve and Plumbing
  • Engine off, ignition off
  • Connect vacuum source to red PVC tube at servo
  • Verify heater valve moves and holds vacuum
Blower Case Flap Actuator
  • Engine off, ignition off
  • Remove blue PVC line going to flap actuators from vacuum controlled solenoid
  • Connect vacuum source to blue PVC tube
  • Verify plumbing and actuator hold vacuum
Vacuum Controlled Solenoid
  • Engine off, ignition off, AC off, temp to 65F
  • Plug the vacuum supply line upstream of the servo and mode control switch
  • Connect the blue PVC line from the vacuum solenoid to a vacuum gauge
  • Connect vacuum source to system from engine bay – pull vacuum
  • Engine off, ignition on, AC mode selector to low
  • Verify the gauge on the vacuum solenoid has vacuum equal to the vacuum in the system from the source in the engine bay.
Assembled Vacuum System Integrity
  • Servo back in car
  • Engine off, ignition off
  • Vacuum source in engine bay, but not including the check valve
  • Verify that system holds vacuum
  • Verify that check valve is unobstructed and functioning
  • Reconnect vacuum system to intake manifold


 
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Old 06-02-2019, 10:47 AM
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Putting the servo back in and adjusting the rods per Kirby Palms 'Book', it occurs to me that the 'condensate' leak isn't condensate, it is antifreeze from a leaking heater core.

Regardless of the source, it dripped onto the vacuum valves in the servo and gummed them up - that's my theory anyway.
 
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Old 06-02-2019, 07:21 PM
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Oh I Hate it when that happens!
You're probably right. That crust Isn't supposed to be there!
(';')
 
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Old 06-03-2019, 06:39 AM
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If you think that it is antifreeze that caused the corrosion, you should correct that issue prior to doing anything else.
Pressurize the engine cooling system up to the system specs (15-16 psi) and verify that the system holds the pressure.
If the pressure drops, search for the leak.
I hope it is not the heater core that is leaking. Not an easy task.
Then again, the heater core is the only component inside the car that is part of the engine cooling system.
Check the hose clamps at the heater core connection.
I had a case once where an incorrect clamp was tightened too much, deforming the heater core pipe and caused coolant to spray into the car.
 
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Old 06-03-2019, 08:20 AM
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It is bumping 100F here and soon to get incrementally warmer as June progresses- July is historically the hottest month in Phoenix. I need AC
..
I bypassed the heater core for now and postponed the ugly task of replacing it to the fall. I want to refinish the dash so it seems logical to tear the whole thing down and do it all at once.

All the actuators checked out ok using a Mityvac and pulling vacuum on the system at the engine, the system held vacuum. However the servo still was not opening the center vent. A vacuum gauge at the servo and vacuum solenoid shows no vacuum. If I jumped the servo to the vacuum line coming into the car, everything worked fine and the center vent opened.

My conclusion is that there is a pinched vacuum hose somewhere behind the center console facia panel. For now I am just going to plumb the vacuum system so I can have AC for the summer and kick the can down the road for fixing everything correctly until the cooler weather in the fall.

Next task is to check the refrigerant side to see if it will hold gas. Need to get a refill on the nitrogen bottle so I can check the system.
 
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Old 06-03-2019, 05:26 PM
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My center vent never did open as it should. At the time I discovered this, I had no access to this or any other Jaguar forum, so I did one of my Work-arounds; I made a small metal device to keep it open. It's easily removable for winter operation.




This straddles two of the center fins in the evaporator.


Easy to take in and out as the season changes.
(';')
 

Last edited by LnrB; 06-03-2019 at 05:36 PM. Reason: add third picture
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Old 06-03-2019, 08:50 PM
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I like the a/c coming out the center vent all the time, not just when the Delanaire guys think it should. I cut a little wood wedge (shaped like a door stop but smaller). Painted it flat black, turned the a/c to max so the center vent opened, pulled the cover off and put the little wedge in there to hold the center vent open all the time. Totally invisible.

Jeff
 
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Old 06-03-2019, 09:43 PM
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Curiously, there was a plastic clip on the vent louvre when I took the cover off the center vent. I suppose that's what that was there for.

I'd like to get the Delanair working again a the engineers intended, but will likely do whatever I need to do to keep the air velocity up at the center vent for the AZ summers.

BTW - Yellow S3 - I've viewed your dash removal video several times in anticipation of pulling it this fall. Thanks for posting it - very useful reference.
 
 
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