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

Finally have HVAC down to one issue: No heat.

 
  #1  
Old 11-30-2018, 07:04 PM
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Default Finally have HVAC down to one issue: No heat.

After years (literally) of chasing this ghost, we fixed 90 percent of the problems by buying this: https://www.jag-aire.com/copy-of-ja-16-details-1

That fixed the A/C issue, the compressor cut on/off issue, a whole bunch of stuff with the servo, etc.

What it didn't fix was the heater. The heater core is getting hot. But we can't get hot air through the vents.

Is there a blend door or something that could be stuck? If so, what are our options for fixing it? I'm not above tying a string to the thing when I want it opened, seriously. I would like, above all else, to avoid removing the dash to fix this.

Jess
 
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Old 12-01-2018, 04:29 AM
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check the Heater Valve operation:

open hood / bonnet
run the engine until warmed up

move the mode selector switch to AUTO.

with a second person moving the TEMP knob from 65 to 85, watch the mechanism of the heater valve to see if it moves open / close. You can see a "lever" moving as you move the TEMP knob.

if it actuates open / close, the heater valve is fine.

at the same time, can you hear the SERVO whirring as it closes and opens Flaps from cooling to heat?

and of course the silly things: is the coolant level correct?

 
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Old 12-01-2018, 08:14 AM
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Originally Posted by JessN16 View Post

What it didn't fix was the heater. The heater core is getting hot. But we can't get hot air through the vents.

Is there a blend door or something that could be stuck?

Yes.

The system is designed to refrigerate all incoming air first and then heat it as needed. When cooling is called for, a door prevents air from passing thru the heater core. When heating (or blending) is called for, the door opens so the refrigerated air can be heated.

Also, when heating is called for, the servo operates the linkages and flaps to divert almost all of the air to the foot well outlets. Is this happening on your car?

Since your heater core is getting hot it suggests the heater valve is OK but do check it as Jose describes just to be sure.

When you select "defrost" do you get any hot air?

Lots of things to check for and different jumping-off points. But, you gotta start somewhere so I'd remove the console cheek panel and, while exercising the control from cold to hot, observe all the linkages and levers in operation. Does anything look stuck/binding/broken?

Cheers
DD
 
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Old 12-01-2018, 08:16 AM
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Originally Posted by Jose View Post
and of course the silly things: is the coolant level correct?
Excellent reminder; often overlooked!

Also, heater cores can be plugged or partially plugged....and/or develop air pockets.

Cheers
DD
 
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Old 12-01-2018, 01:28 PM
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also: hanging next to the battery there is a one way ball check valve inline with the vacuum hose that connects to the servo. This plastic black and white valve tends to clog with time affecting the a/c and the heater system.

remove it and blow through it. Air should escape one way but not the other. If clogged, the ball inside won't move. Put it in a pan of warm water to try and unclog it.

before removing it, observe the orientation of the arrow marking on the valve body.

 
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  #6  
Old 12-01-2018, 04:56 PM
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Originally Posted by Jose View Post
check the Heater Valve operation:

open hood / bonnet
run the engine until warmed up

move the mode selector switch to AUTO.

with a second person moving the TEMP knob from 65 to 85, watch the mechanism of the heater valve to see if it moves open / close. You can see a "lever" moving as you move the TEMP knob.

if it actuates open / close, the heater valve is fine.

at the same time, can you hear the SERVO whirring as it closes and opens Flaps from cooling to heat?

and of course the silly things: is the coolant level correct?
There is no heater valve in this car anymore; we have a manual ball-and-handle valve installed in the heater core intake line and we turn it off in summer months. The vacuum line that used to feed it is plugged off. When you turn off the car and everything begins to rest, the dashboard will get warm over the course of 5-10 minutes. I'm assuming this means the heater core in the car is radiating heat that can be felt over time. That's why I feel pretty confident it's going to be a blend door issue, so I mostly want to figure out how easy/hard it is for me to either manual-ize that operation, too, or repair what's broken. If it involves taking the whole dashboard out, my shop is balking on that.

Jess
 
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Old 12-01-2018, 05:05 PM
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Originally Posted by Doug View Post
Yes.

The system is designed to refrigerate all incoming air first and then heat it as needed. When cooling is called for, a door prevents air from passing thru the heater core. When heating (or blending) is called for, the door opens so the refrigerated air can be heated.

Also, when heating is called for, the servo operates the linkages and flaps to divert almost all of the air to the foot well outlets. Is this happening on your car?

Since your heater core is getting hot it suggests the heater valve is OK but do check it as Jose describes just to be sure.

When you select "defrost" do you get any hot air?

Lots of things to check for and different jumping-off points. But, you gotta start somewhere so I'd remove the console cheek panel and, while exercising the control from cold to hot, observe all the linkages and levers in operation. Does anything look stuck/binding/broken?

Cheers
DD
The Jag-Aire switch acts as a compressor defeat. With it installed, selecting "HEAT" kills power to the compressor according to my shop (I haven't been in the car to test it myself). So the pre-cooling may be a thing of the past for me.

That also means I haven't tested what the servo is doing with the vent control yet. Prior to yesterday, when they installed the switch, every vent on the car blew air. The shop didn't indicate things had changed, there.

I've never seemed to get any hot air anywhere, defrost vents or otherwise.

The one thing the shop did mention is that with the switch installed, the system is *trying* to respond to changes in the temp control wheel when selecting different temperatures. With the fan switch at AUTO, the fans were increasing/decreasing speed in response to inputs on the temp wheel. Until now, the car would do that in some cases and not in others. Obviously I'll have to drive it for awhile to see if that issue is going to remain intermittent.

At least it doesn't seem to be doing what it used to do -- going haywire and only wanting to function with the mode switch set to "DEF."

Jess
 
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Old 12-01-2018, 05:07 PM
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Originally Posted by Jose View Post
also: hanging next to the battery there is a one way ball check valve inline with the vacuum hose that connects to the servo. This plastic black and white valve tends to clog with time affecting the a/c and the heater system.

remove it and blow through it. Air should escape one way but not the other. If clogged, the ball inside won't move. Put it in a pan of warm water to try and unclog it.

before removing it, observe the orientation of the arrow marking on the valve body.
Does this check valve directly (and only) affect operation of the heater valve at the firewall? If so, that system is no longer; it's all controlled by a manual ball-and-lever valve.

If that check valve sends some kind of vacuum signal back to the A/C brain, I'll look into it.

Jess
 
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Old 12-01-2018, 08:13 PM
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Originally Posted by JessN16 View Post
Does this check valve directly (and only) affect operation of the heater valve at the firewall? If so, that system is no longer; it's all controlled by a manual ball-and-lever valve.

If that check valve sends some kind of vacuum signal back to the A/C brain, I'll look into it.

Jess

The system does depend on vacuum supply to operate some of the doors and flaps so, yes, check the check valve for correct operation and make sure it is getting vacuum....which comes from a vacuum canister tucked into the LH inner fender near the firewall.

Cheers
DD
 
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Old 12-01-2018, 08:26 PM
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Originally Posted by JessN16 View Post
The Jag-Aire switch acts as a compressor defeat. With it installed, selecting "HEAT" kills power to the compressor according to my shop (I haven't been in the car to test it myself). So the pre-cooling may be a thing of the past for me.

I don't think compressor cut-out is the intended operation of the switch.

The switch is intended to replace the amplifier. The amplifier is the 'brain' of the system which, using sensor inputs, provides automatic fan and temp control. The amplifier, gives commands to the servo.

The servo might be called the 'robot' of the system. It mechanically operates the flap linkages, vacuum switches, and fan speed switches.

My understanding of the switch is that selecting warmer or colder should result in the servo operating just it would if being commanded by the amplifier. So, when changing from warmer to colder with the new switch you should hear the servo whir, the flaps flapping, etc

Cheers
DD
 
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Old 12-02-2018, 12:40 AM
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Originally Posted by Doug View Post
I don't think compressor cut-out is the intended operation of the switch.

The switch is intended to replace the amplifier. The amplifier is the 'brain' of the system which, using sensor inputs, provides automatic fan and temp control. The amplifier, gives commands to the servo.

The servo might be called the 'robot' of the system. It mechanically operates the flap linkages, vacuum switches, and fan speed switches.

My understanding of the switch is that selecting warmer or colder should result in the servo operating just it would if being commanded by the amplifier. So, when changing from warmer to colder with the new switch you should hear the servo whir, the flaps flapping, etc

Cheers
DD
Over the past couple of years, sometimes you can hear servos at work when you switch between modes and sometimes you can't. I'm picking the car back up next week and I'll see what all is different after the installation of that switch.

Jess
 
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Old 12-05-2018, 11:20 PM
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Originally Posted by Doug View Post
The system does depend on vacuum supply to operate some of the doors and flaps so, yes, check the check valve for correct operation and make sure it is getting vacuum....which comes from a vacuum canister tucked into the LH inner fender near the firewall.

Cheers
DD
Quick update ... we are getting no vacuum to the valve. We suspect the line is plugged/disconnected wherever it hooks in. I'm going by the shop tomorrow to follow up and check progress.

Jess
 
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Old 12-06-2018, 10:15 PM
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Checked in with the shop today, felt like I'd been told it had a terminal disease.

First, to clear up something from earlier, the compressor is NOT turning off with the Jag Aire switch. It's not supposed to anyway, but something made them think it was earlier, and it wasn't.

They took out the glove box and disassembled the lower dash on the passenger's side to expose the linkages. The linkages do cycle with the Jag Aire switch. One of them (the one that is anchored most highly on the HVAC box) has a tendency to cam too far over and stick, and then must be moved back manually. Obviously that's going to be an issue when the car is put back together. We can't figure out what doors it changes, anyway. Maybe the fresh/recirc feature? Don't know.

They've gotten hot air to come out of the floor vents. That's progress, because we never have had that before. But when the system is set to full heat, I've got ice-cold air coming out of the dash and defroster vents unless you manually unplug the compressor. Then, you still don't get anything better than lukewarm air out of the face vents but again, I'll take it.

Nothing you do to the Jag Aire switch or the factory knobs allows you to direct air completely to the floor, dash or defroster vents. Air is coming out of all of them all the time.

In order to get hot air to the floor vents in Heat mode, you still have to close part of the system manually. Then when you shift back to A/C, it won't go back unless you manually send it back. So we're working on some kind of choke cable/manual pushrod to hook in there so I can manually cycle the system. We're also going to have to mount a compressor kill switch in the other ashtray. And then we still don't know what we're going to have when it's going down the road in cold weather.

Basically I think every part of the system is jacked. The amplifier was bad, and the Jag Aire switch fixed that, but either the servo and/or ALL the blend doors and actuators are also malfunctioning. We've already had to remove the factory heater core valve and put a manual valve in, and we've got vacuum issues in the system, too.

Combined with equally bad experienced with my system in my 89 Jag XJS (a D-III system), where I'm getting ice cold air in the footbox and hot air out of the defroster vents, you'll never hear me say anything nice about a Delanair HVAC system.

Jess
 
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Old 12-07-2018, 08:19 AM
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That is right, the jag-aire switch just replaces the amp and temp sensors. I have one in my 79. I strongly suggest adding a toggle switch that controls the compressor. Switch off = no cold air so you are halfway to better control. Your manual hot water valve is the other half. Yes, in heat mode the only air comming out is those tiny vents by your knees. Defrost gives you full a/c and full heat to the defrost vents. If you have total control over hot water and a/c compressor the defrost setting makes it easy to diagnose. Get a drawing of the levers under the left cheek panel. I checked my car against the drawing and discovered I was missing a little spring that pulled the rod back. Just keep studying the drawings and diagnosing and you eventually will get it working ok. Took me a whole summer but now it works ok (note I did not say like a modern car).

Jeff
 
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