Getting closer to having AC!

The interior electro/pneumatic AC components all appear to be functioning, the new compressor and drier are installed and the system is full of refrigerant.

But there's no power at the compressor clutch (the ac tech powered up the clutch with a jumper to charge the system and didn't want to touch anything inside)

Checked for clutch voltage at the output of the RANCO thermostat and I have power. Checked the fuse on the wire going out of the RANCO - it's good. Checked the continuity from the end of the fuse to the compressor clutch, and there's nothing, so there's a broken wire somewhere between the cabin and the fan clutch. (when I first started this repair the clutch fuse was burnt out, so that wire probably shorted somewhere and then eventually broke because now it measures open)

So rather than trace that bad wire through the engine bay, I'd just rather run a new wire from the RANCO fuse to the compressor clutch.

So my question is this - where is a good place on the firewall to shove a single wire through on a S3?

 

Not easy to find a good spot on a Series III.

The area above the pedals, where the throttle cable enters the cabin, is a good spot, IMO.

That said, shouldn't be too hard to trace the open circuit. There's a bulkhead connector under the battery (LHD cars). From there the compressor wire (among others) runs low along the RH wall of the engine bay to a multi-pin connector. From there the wires branch out. The compressor wire runs, roughly speaking, under the p/steering pump, then upwards across the front of the cylinder head, then down to the compressor. The fault could be anywhere along the line but I strongly suspect you'll find it between the p/steering pump area and the compressor itself. The wires at the front of the cylinder head, in particular, take a real beating

This ^^^^ assumes a six cylinder Series III

Cheers
DD

 

I was very interested in the HC-12a stuff, so I researched it a bit.
It contains Propane gas ( R290) and Isobutane (R600a), both excellent refrigerators but also good for cooking, ergo highly flammable.
Several sources tell me the use of RC12a is therefor forbidden in most countries.....nah....won't touch that....highly flammable gas in combination with a V12 heat plant is not such a good idea imho...

 

at the firewall, driver side, behind the brakes booster, there is a spongy rubber yellowy plug with 4 holes, one of the holes is occupied by the cruise control metal cable. The other 3 holes are sealed.

if you pierce one of the remaining 3 holes with a straightened clothes hanger, you can slide a wire through it to the interior.

if you remove the dash cap, you can pull and route the wire neatly using stick-on plastic wire clamps.

once the wire is no longer moving, seal the hole around the wire with caulking.

 

I've used the location Jose described with success. Another technique that I use when running a wire through the firewall where there are sharp metal edges is to push a short piece of thick walled vacuum hose through that area and then push the wire through the hose. That gives it some extra protection.

Jeff

 

Thanks for everybody's input - this board makes owning a classic Jag possible.

Couldn't sleep this morning and got up and traced the wire across the front of the engine - what a mess. It looks like it goes into the loom in the right -forward corner where the right inner fender meets the radiator support. I'm going to open up the loom in that corner and see if I can get continuity back into the cabin, and if I do, make the wire replacement start there. Now I'm wondering what else goes through the front of the engine that's going to be in bad shape too.

Tried that yellow plug on the driver's side where the hood release cable goes through the firewall with a piece of welding rod and could only go in about 6 inches and couldn't see it poking though from the cabin. (Jeff I'm going to follow your youtube video on getting the dash apart to refinish it - another summer/lockdown project

Seems like in the new pandemic reality of shelter at home,. a two hour project seems to stretch for days, Soon I'll have ac in the car to hunt toilet paper in comfort.

Phil

 

I would be going crazy during the lockdown if I didn't have my cars to work on. When I was a kid, before cable TV, social media, etc etc. On Sunday afternoon for entertainment we would all pile in the car and go for a Sunday drive. Not to a destination but just to get out of the house. We have been doing that in the Jaguar just to enjoy the car and see the spring foliage.

Regarding the wiring, on several old cars I have owned over the years I would just pull a new wire from point A to point B and zip tie it to the old cloth loom covering. Eventually, over time I had replaced every wire then I cut out the old bundle and wrapped all the new wires. Sort of a slow motion replacement until the entire car was rewired. Of course the wire colors didn't match the old ones but it was safe and dependable.

Jeff

 

My Jag has been one of my more reliable cars, but lately it's given me cause for concern. The ignition amplifier went out a few weeks ago and I replaced both coil and ignition amplifier with a Petronixs units. But on my last joyride to the junkyard to look at a XJ6 for parts at the pick-and-pull on the other side of town (102F day), the engine missed a beat then the tach swung to full scale as I turned into the entrance to my subdivision, then was normal as I motored to the house. Tried a restart a half hour later after a full heat soak and it started right up..

I'm wondering if I have a dodgy ignition switch too.

Surely the life of the Petronix components is more than the couple of hours I have on them. Recalling Doug's diagnostic advice, I hard-wired a lead to the positive side of the coil with and alligator clip on the other end standing ready to provide a direct battery power source to the coil so I can bypass the ignition switch it if does it again.

The tech at the AC shop told me that my fan clutch was bad and not putting out much air. He said that if the fan continues to run after the hot engine is turned off, the clutch is bad. Has me wondering if lack of cooling air to the new Petronix amplifier is causing problems with heat. New URO fan clutch on order from RockAuto, so we'll see in a couple of days.

The Jag has never overheated, but on warm days in Phoenix it will bump a little past 90C on the gauge. High hopes the new fan clutch makes the temp gauge read high 80s all the time, cools the amplifier and gives the ac condenser adequate airflow. There's a 15" electric fan in the junk parts inventory that might get repurposed to replace the puny Jag aux pusher fan to give the condenser a little more cooling if the R134 charge falls short of expectations for vent temp

Really want to take the Jag out for a joyride to relieve pandemic induced cabin fever, but don't wand to come home on the end of a tow hook.- just need to run down a few more problems first

.

 

in the 30 years of owning my XJ-6, yes thirty, ( treinta ), I have never heard of a fan clutch being bad because the auxiliary fan came on after the engine was shut or came on during driving.

the auxiliary fan circuit is designed to do just that.

instead of modifying the heater valve which is designed to open and close when in a/c mode (temp knob at 65), you can modify the auxiliary fan circuit to run constantly when in a/c mode as it was done by the factory with the 12 cylinder engines. The auxiliary fan will still keep running after engine is shut down if the temperature is above the radiator's thermal sensor pre-set temperature, and it will shut off by itself when the temperature is below the thermal sensor's pre-set temperature.
This mod will keep the coolant temperature and the gauge below 90 in extremely hot ambient temperatures and in traffic.

second to that, get rid of R134a refrigerant, instead charge the system with Freeze12 or any other of the alternative refrigerants available today. R134a is cool but not cold unless the car's system was optimized for it by the factory. The XJ-6 system was optimized for R12, not R134a.

 

You wrote ".....never heard of a fan clutch being bad because the auxiliary fan came on ....."

I was sipping Bulleit bourbon when I wrote "He said that if the fan continues to run after the hot engine is turned off, the clutch is bad." That might have been ambiguous as to which fan continued to run - engine or aux. The tech told me the yellow engine cooling fan should stop with the engine but it continued to spin once the ignition was turned off. He went on to say the engine fan took a "couple of minutes" to come to a stop and wouldn't blow out a Bic lighter when it was turning with the engine on. Mechanic hyperbole, but I understood his point.

I've not had a fan clutch fail in 50 years of driving/owning all sorts of cars, so I was kind of surprised when the tech told me it was bad. In summer traffic at idle, the Jag's temp gauge will increase 10-15C over 80C, but the aux fan has never come on and I assumed the cooling system was functioning normally. The tech said coolant temp should hold rock steady on the thermostat and cautioned me not to run the ac unless the fan clutch was working properly, because if I did the head pressure could rise to levels that would damage the system. (R134 has higher head pressures anyway which exacerbates the issue.) My 'belt and suspenders' solution was to replace the fan clutch and install an even bigger electric aux fan wired to run with the ignition on to keep the coolant temp/head pressures in check.

I have R12 on the shelf at home, but the ac tech assured me I wouldn't be able to tell the difference with R134 so we'll see. If my vent temps don't meet expectations or if I lose refrigerant over time, will have to re-evaluate use of R12 or Freeze12

 

ohhh that is different, then yes you had a bad fan clutch and too much bourbon scotch.

if the auxiliary cooling fan, (the electric one in front of the radiator), never came on, then you had a bad Red Relay, the chinese red one mounted on the radiator support and/or a bad thermal sensor-switch located at the bottom right side of the radiator.

but if not that, then it was the aux. fan Fuse located in the engine compartment's 5-fuse fusebox located near the coolant filler-expansion tank.

the auxiliary fans themselves rarely go bad but easily tested straight from the battery.

also you should consider the auxiliary fan mod, not too difficult to do and in the Arizona heat, neccesary. It is reversible for fall through winter when it is not needed.

One warning is that the fan mod is noisy outside of the car. Sounds like a Maserati 8 cylinder in a red light.

 

I can tell you from my own experience, you WILL be able to tell the difference if you only shoot in R-134 and make no other changes to the system.

There! I've said it!
(';')

 

Well, the decision to use R134 was kinda the result of the current COVID situation.

The neighbor with the stash of R12 is 80 years old. Getting additional refrigerant if I need it is problematical.

An engineer friend retired years ago and opened up a auto repair business at a shop at his house. He's pretty cracker-jack with automotive AC systems and has all the pumps. scales, gauges, sniffers, etc and I've been taking my ac problems to him for the last 25 years. He's 72 and I need to stay away from him.

Another friend of mine does automotive ac work too. For the last 18 months, he's been coming over Saturdays to work with me on my car projects. He helped me diagnose the bad compressor last summer. The wife says 'no more' and is pretty spooked about risk. (Not going to say what she said she'd do if it didn't stop)

To get ac before the summer heat hits, the easy way out was to drop the Jag at the AC shop and pick it up when it was done. They wanted to use R134

There's no doubt that R134 is sub-optimum. Head pressure is higher, molecules are smaller making the system more prone to leaks, the condenser isn't big enough and the expansion valve isn't quite the right orifice size, But nothing is forever (I hope) and if I can't live with R134, I can change it to R12/Freeze 12 in the future.

 

He's right




No big deal; so long as it doesn't keep going up-up-up

Don't get your hopes up too high.

In my experience the cooling systems on these cars have enough capacity to hold coolant temp to thermostat rating up to about 90ºF ambient conditions. After that, the coolant temp will increase.

Cheers
DD

 

You've been unusually lucky!

Well......

Yes and no. Some cars will, others won't. Depends on how much designed-in cooling capacity the system has.

Ideally a cooling system has the capacity to over-cool under all conditions, leaving the thermostat to cycle a bit to maintain a fairly constant minimum temperature. But, some cooling systems just can't do that. So, the temp does increase under some conditions.

Plus, many cars have a heavily dampened temp gauge that reads 'normal' over a wide range of temperatures, giving the impression that there is no change in actual temperature. Jaguar itself threw-in the towel back in the mid-90s, joining other car makers in using such a temperature gauge. My '95 XJR had such a temp gauge. Rock solid, dead center needle reading from 170ºF to about 210ºF actual coolant temp.

Cheers
DD

 

Thanks to all that offered advice and guidance, The AC is working fine now almost $500 later.

Some observations that may help others...................

• As Doug said, the wire feeding the compressor clutch takes quite a beating. I intercepted the lead to the compressor just underneath the air cleaner and rewired it so it went over the radiator instead of across the engine, The AC clutch wire is not part of the Jag wiring harness but has its own connector right under the air cleaner so I rewired it from there.. Connector location noted right on the SK drawing had I bothered to read it.
• The thermal fuse tested good on the bench but when I installed it, it showed a high resistance. NAPA had a replacement for $5 as it is a pretty common GM AC part. The part number is 6551258,
• Ambient was 99F today and the new fan clutch held 80C on the gauge until I turned on the AC and it jumped to 90C which indicates to me I am just at the limit of the cooling capacity on the thermostat.at this temperature. I would expect the coolant temp to march in lockstep with ambient temps up to the 120F (about 11C increase on the gauge which would be 105C) we can experience in Phoenix in the summer. The aux fan is wired to turn on with the ignition but covers very little of the face of the condenser. Next logical step might be put a couple of fans on the face of the condenser to replace the aux fan.
• Not sure what the vent discharge temp is on the R134. I have a digital thermocouple I will put on it and see. Seemed considerably cooler than ambient, but really need to take it for a drive and let all the temps stabilize. I can feel cool air coming out the defrost vents so my seals must be shot. Will seal them up when I refinish my dash.
• The new fan clutch is significantly noisier. Once warmed up, the idle RPM in neutral dropped about a hundred RPM. If you need one, they are about $50 at your door from RockAuto. URO brand. Did not like the slotted holes where it mounts to the water pump but seems to work ok. Pulling the top fasteners holding the fan shroud to the radiator and pulling it back towards the engine helped considerably in getting the fan and clutch out.
• Found a disconnected vacuum hose on the intake. Plugged it and idle smoothness improved considerably, Even acceptable now. Thinking about ginning up a smoke machine from an old soldering iron, mason jar and baby oil to check everything else out. Will report results if I do.