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

Heating problem/oddity Delanair Mk II

 
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Old 02-08-2019, 09:44 AM
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Default Heating problem/oddity Delanair Mk II

My climate control has been working well in all respects until recently. Something a little weird is going on when heating is called for.

If max heat is called for (85 on the temp control) I get cold air thru the footwell outlets. The small amount of air from the outboard dash outlets is warm, as expected.

However......

If I dial back the temp control just a bit....just enough to take it off of 'max heating'.....I get warmed air through the footwell vents and outboard dash vents, as expected.

Weird, huh?

Unless someone has a been there, done that answer it looks like I have my work cut out for me. Of course the easy solution is to simply avoid the max setting....but my curiosity is getting the better of me. Since snow is predicted this weekend I'll have ample indoor time to study my Delanair manual....and hope for an epiphany

Any ideas?

I'm wondering if a flap is over-rotating?

Cheers
DD







 
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Old 02-08-2019, 09:49 AM
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the temp rheostat has a dead spot?
 
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Old 02-08-2019, 10:33 AM
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Way beyond my reckoning of Delanair!!

But, I suspect that it takes a bit for the warm air to heat the ducts, and as such a delay is involved. let it ru a bit and the ducts warm up and the occupants get warm air..

And, no use over the warm months has delayed operation. AKA use it more !!!

I ain't going anywhere today. It went well yesterday !!
Just exercise it in summer for warm as one exercises the cold in winter for summer.... , .
 
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Old 02-08-2019, 11:13 AM
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I agree with Jose.
Jag-Aire has a test procedure for the rheostat, I think on his site, www.Jag-Aire.com..
He had me test my whole system before he would sell me a new Amp.
Requires a 9v battery and ohm meter.
(';')
 
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Old 02-08-2019, 11:34 AM
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Right! One of my tests will be to bypass the amp and drive the servo on the red and purple wires to see if anything changes.

Cheers
DD
 
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Old 02-12-2019, 04:29 PM
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Check the resistance sweep of the feedback potentiometer ,located on the end of the servo shaft. This can be monitored from the multi plug connector at the climate amplifier. I would also check the set screw that holds the 2 flap blend rods and linkages onto the gearbox cam mechanism. I have seen this screw unwind and cause the mechanism to run out of true.
 
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Old 02-15-2019, 10:21 PM
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Problem solved. It was a low tech issue. In nutshell....

I did some memory-refreshing (using my Delanir MkII training Manual) and fairly easily (although not quickly!) determined that all the flaps and linkages at least seemed to be doing the right things. Rather than go further into those weeds with no evidence as impetus, I decided to explore other possibilities.

Long story short.....

The heater core was partially plugged or had an air lock. Or both.

Rigging-up some hoses I observed that, with light-pressure water from the garden hose, flow through the core looked OK. However, using gravity-flow only, water would flow through quite easily at times....yet, other times, not flow at all. Zero.

I decided to fill the heater core with a radiator flush product and let it sit overnight. I then pushed-though about 5 gallons of water with the garden hose. When the output matched the input I decided it must be OK. I never saw anything gunky come out, though. Nor was there a build-up and sudden release as you might expect if a clog was dislodged. I don't think it was clogged. A bit restricted, perhaps? I dunno.

As suggested in Kirby's book I added a flushing tee to the heater core outlet hose so I could purge air from the core more easily. Running the engine revealed lots of bubbles exiting the heater core....along with the coolant, of course. After about half a gallon the bubbles stopped so I capped-off the tee and then bled the rest of the system per usual via the bleeder at the radiator. The heater now works great.

I think the true problem was an air pocket in the core. The 6-cylinder cars don't seem prone to cooling system air locks but the V12s certainly are.

Cheers
DD







 
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Old 02-16-2019, 02:11 AM
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Many cups of coffee in that repair I bet.

Well done.

Yep, the V12, she be a beast on its own.
 
 
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