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85 XJ6 Heater Core Replacement Advice Wanted

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dvr

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I have been reading up on this difficult procedure. Haynes manual is confusing as it refers mainly to series II cars and I don't know if series III heating set up is the same. Jagbits tech page 1 offers a short cut but I am not clear on some of the steps. Eg: "disconnect steering column at lower mounting point". Does the steering wheel need to come off first or does it come out as a unit? Also, it states, " carefully cut heater pipes as close to the steel side panel and the coolant temp sensor as possible" Where is the coolant temp sensor and which side panel? Is this a valve, or is that the vacuum valve on the firewall in engine compartment? I need to have a working heater/defroster and can't replace the carpet until the leak and rust is repaired. Is there a manual specific to series III that would be helpful in this case? Anyone with expertise in this matter? Many thanks for any input.

Dan
 
Ok, cutting the pipes will save some time, it is considered the uhm "butchers" way of proceeding.That said, you can disconnect the wiring to the steering column, unbolt the column, wheel and all, and take it out whole. Make sure the wheels and steering are straight before doing this. Pay attention to the location and number of shims. The series 2 and 3 are pretty similar, but not exact. If you choose to do it the "correct" way, then take photos as you disassemble things. Mark connectors, as there are 2 or 3 that will fit one another, but not be correct. Be extremely careful disconnecting the AC hoses from the evaporator in the engine bay.If there is any doubt on the large hose, cut the "nut" with a dremel tool, and sacrifice the hose, as OEM evaporators are NLS, and the aftermarket ones are not-so-good. It is a great time to detail clean all the dash parts. I think it is easier to take the front seats out, but it is not totally necessary. The console has to come out to do the carpet anyway, so you might as well do the big job. The coolant sensor BTW is located on the coolant pipe under the dash, near the steering, and is a little plastic device with 2 wires connected to it. It keeps the fans from turning on until the coolant warms up. You should get one of the JDHT factory manuals on CD. Most include the "parts books" as well. Cheap, and a really good thing to have.
 
Thanks Jesse:

I think I'm going to dismantle everything. The weird thing is that I flushed the heater core both ways and it was amazingly clean. I want to see where it's leaking from first. The fans blows cold air so the hot coolant is not circulating through the core. How do I get the coolant flowing through to test it? I am going to redo the veneer on the dash and I am debating whether I want remove the trip computer and put a vacuum gauge and A/F gauge in its place. Thanks for the info..

Dan
 
Um....you're changing the core because of not heat, not because of leaks, right?
Heater control valve for hot water. Has to be one somewhere. When you select "cold" it closes, OR A/C. Vacuum operated, if I recall. Not enough room under the dash, I think it's on the engine side, mounted on the firewall. Usually, by 86, black plastic.
Follow the heater hoses, find the valve (one heater hose in, one out) with a vacuum line on top of the valve. If the vacuum line is on, and intact (as in, not broken), run the car until warm, using a hand vacuum pump, fit to the valve and draw a vacuum. See if you get heat.
If water flushes through the core, it isn't the core giving you NO heat.
 
The core did leak in the past as evidenced by the rust on the driver side tunnel and floor pan. When flushing the core yesterday there was some leakage. So with water/coolant flowing through the core and fan on there should be heat. The heater control valve is on the firewall engine compartment. I removed it and got it to work smoothly. With vacuum applied it closes the valve. Is that correct or is it malfunctioning? I don't understand why no heat if coolant is flowing and fan/defroster on unless the air is not flowing through the core.

Thanks
 
Yeah....some valves vacuum close, some vacuum open, if your vacuum closes, must be right.
I didn't see the part of the rust on the tunnel.....but....it's a Jag, who knows where it's leaking from. Windscreen, wiper towers, never know.
If the blend doors aren't open, no air can flow through the core.
Should be a door to close off the core, and another to blend heat in a bypass.
Rusty hinges, vacuum issues, rat's nest (or squirrels), never know. Something climbed in and built a next, the door won't move.
See if you can find them, disconnect the actuators, and manually move the doors.
If you're going to tear it apart, find out what's wrong first, so you know what to fix when you get the box out.
Just a comment....on MK2's and I think "S" type, unless the scuttle (cowl) vent is open, you will get no heat.
So, look for the air inlet, look for blend doors stuck shut, bad actuators, etc.
Look for scuttle drains plugged up...that'll five you water in the people part.
Dave
 
So the temp control knob controls the heater control valve via vacuum. So the heater valve vac source needs to come from the temp control knob vac source not straight from intake vacuum source. Otherwise the valve would be closed any time the engine is running. That means that the vac line to heater control valve is not hooked up correctly. Does that sound logical?
 
Could be anything. Quick check would be to run the engine, pull the vacuum line, see if there is any vacuum present, move the heat knob to the other end, and re-check. If vacuum is present, it works.
Now.

There should be a vacuum reservoir somewhere, and a check valve, and associated hoses.

If that heater is anything like other Jags, there is some sort of a control box that fails (it's been a long, long time since I worked on one) that takes the signals from the temperature knob, the sensor on the inlet to the core (won't come on until it's hot), defrost signal, all of that, and sends out the appropriate vacuum command.

Maybe yours is different....but if you've got a vacuum line at the heater control valve, it's a system based upon vacuum control.

Find the blend doors under the dash. Another one will be defrost (runs up to the vents). Engine running, operate defrost and see if the arm moves.

Find the vacuum source on the engine (inlet manifold), follow it, looking for dry, cracked, split or crumbled lines (never happens on a Limey Limo, I know), looking for a vacuum reservoir. Make sure the reservoir is solid, lines are good, as usually underbonnet stuff, with engine heat, fail first.
 
You did check fuses first, right? This is electrical/vacuum/mechanical. The box controls solenoid valves that allow vacuum to pass to those actuators.
Fuses is where I'd go and just make sure with a test light they all have power on both clips.
It is manifold vacuum, check valve, reservoir, and the solenoid valves, THEN the actuators.
The test at the heater control valve will rule out any vaccuum or electrical issues.
See if any of the actuator motors work, as if any do, you will know you have vacuum and power.
 
Wait wait...If you rotate the knob from cold to hot, do you hear a whirring noise as the servo cycles? The servo is the electro mechanical device that opens and closes the blend doors, and opens and closes the vacuum valves that control some of the vents as well as the heater valve. The servo is directed by an amplifier in response to the temp knob being moved. Not uncommon that the amps fail. Less common, but not unheard of for the servo to fail. Key on, switch on the ac/heat unit. Set to coldest temp. Servo should cycle, fans should start up, the center vent should open, and theoretically cold air would come out, with a small amount of air coming from the footwell vents on the side of the console.Switch to hot. Servo should cycle again, fans slow down, stop, and restart as the servo gets to the end of its travel (depending on coolant temp).Center vent closes, and all air (should be hot) comes from the footwell vents. Check this out and report back. Good first place to start. Not too likely that the heater core rusted the floors. More likely the windshield leaks, or has in the past.
 
Well, I don't hear any servo noises. I believe there is a vac canister on driver side w/ vac line attached. Will check all fuses tomorrow. I do know that the windshield did leak. More investigative work to do... Will report back tomorrow.

Thanks Guys.
 
Jesse, is 86 still electrical/mechanical? Last ones I worked on were electrical/vacuum, as the vacuum to his heater control valve.
Vacuum actuators on the right side, positions sensors on the left side of the box?

Or, is this like the S type with an amplifier and motors?
 
All the US series 3s have the servo motor and amp.

If the servo does not move, then you need to find out which componenet is bad. Hunt down the servo connector on the right side, behind the console side cover. It is a weird round connector. Disconnect the connector. On the servo end, find the red and purple wires. Put power to one, and ground the other, and see if the servo moves. Then switch the power and ground.(In case the servo is already moved to the end of the travel) If the servo moves, the amplifier is bad. Contact the usuals for a replacement. There was a cheapish aftermarket one available.. . If you cannot find an amp (possible), then there is a way to manually move the servo. On the left side, find the connector to the amp. It is also round. MAKE SURE YOU KNOW WHICH END GOES TO THE AMP!!!! It is the end w/ the male pins. You can cut the connector off of the amp. Cut off all the wires except the red, purple and brown. Plug it back in to the car end of the harness. Then the brown provides power... Connect to R/P and ground whichever one not connected to the B on whatever is convienient (Heater case is right there). I forget which wire moves it which way, so experiment. Move the servo to whatever position you wish. Disconnect your new tool, and store in the glovebox for the next time. If the servo does not move, and you are SURE that you have tried good power and ground in both directions, you will have to track down a servo. I think they are NLS, but good used are not too hard to find. Mark the positions of the rods (it will be obvious what I mean), and re istall them in the same place. These control the blend flaps.
 
Most of my experience was Series I, some Series II. Don't recall doing heater stuff on a III.
He should still have a hot core if the vacuum works, unless it's a solenoid valve for the heater valve vacuum.
 
OK Guys, here's todays update... The good news, heater core is not leaking, hot coolant flowing. Checked fuse # 16 for ac and heater motors. I have current to both pins, I can hear the servos and see the vac actuator work on the driver side of heater box. With heat control on high temp and fan on either low, auto, high, or defrost, I still get no heat blowing. Checked coolant temp sensor on heater pipe and it has continuous power. Also, now the fan isn't working (was blowing strong earlier). Is there a relay or is it ignition switch related? Or bad ground? More diagnostics to be done. At least I can carry on with the re-carpeting. Coted the floors with por-15 toaday. Thanks so much for your guidance as this is a bit complicated. If I had a diagram of the heater box and doors, etc. it would be easier to figure out. I like a good challenge and this car will provide that for me. Will keep you posted.

Cheers,
Dan
 
If in doubt about the coolant sensor on the pipe, just connect the wires together. If I remember correctly ,there is a 50 amp fuse for the blowers. Check the fuse carefully. Lucas fuses are not the same as US fuses. There is a wire soldered to both end caps, and it melts at a certain amperage. What can happen on the 50 amp ones is that the solder melts, and it works when the wire touches. Can be hard to see...Bend the fusebox terminals to tighten the connections. If you have coolant flowing into the heater core you should have heat. Even if it comes out the wrong place. If you switch to Def,the system should go to full hot, and air should blow out the ducts on top of the dash. (If you have a vacuum leak, defrost ducts open all the time is the default) There is a blower relay (specialized part!!) under the left console cover... I have never had to replace one, but the cars have never been this old before. I will root through the archives and see if I have a spare climate control manual or wiring diagram set. I will let you know in a day or two.
 
Looked at the wiring diagram today. There is a blower speed relay. Schematic shows it near the motor. I am trying to find out why, suddenly, I have no fan at all. Still thinking it could be a bad ground since it has worked fine, not worked, worked again, etc.. Also, there must be a rusty blend door not allowing air flow over the core. Does anyone have the Delanair Mark II Automatic Climate Control System Service Manual? I hear that it is the sacred text to understanding the heating/ac system. Without schematics/diagrams it's tough to figure this out. I need the heater/defroster working this winter/spring. I'll worry about the ac later. Any help is appreciated.

Dan
 
I will look this weekend. I keep a set O stuff in the shop library for my reference, but I think I have another copy. The blower relay is a large relay located under the left console side cover. It has a LOT of wires connected to it.( not the usual 4 or 5 pin relay)
The servo manually moves the 2 more or less vertical rods, and they move the blend doors. Vacuum moves the defrost flaps, heater valve and center vent, as well as the recirc flaps on the bottom of the blowers.

OK, I went and looked. I have several sets of series 2 factory training info. I have one genuine series 3 factory training on the climate control. The S3 stuff is more detailed than the S2 info, although the systems are substantially the same. Maybe a few different wire colors, but still the same system.This is the stuff they trained the factory techs with. I will see about having it copied. Problem is I am swamped with work here, so it'll take a few days at least.
 
It appears there is no current to the lrg brown/wht wire to the blower speed relay. Possible gremlin involved.
 
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