Hi all,

Appreciate any ideas here. I'm sure its something simple that I have overlooked. Going into winter realized that I was not getting heat from the climate control system. At first glance everything else seemed to be working. Here is what I have checked so far
- Fans operate at all speeds and change automatically as it calls for different temps. Def mode diverts all air to windshield, but its cold
- Hot heater core - heater core outlet hose gets hot when engine warm. And while I was at it checked operation of the water valve (although failure mode is open and full heat anyway)
- Vacuum at controls. have verified I have vacuum at the controls by checking if the vacuum actuator at the right hand of the box operates
- Servo operates. By using a heat gun (on low setting) at the in car sensor, the servo operates and moves the operating rods on the right side of the box
- I have disconnected the rods from the servo unit and the tensioning springs and moved the flaps manually. I can hear what seems to be the flaps hitting the stops in there, so it seems they are still connected to pivots and operating. Also moved the rods manually to see if I could get air over the heater core with no luck.

I have attached some pictures we can use a reference. Appreciate any and all ideas here.

 

Are you thinking that the cooling flaps are not closing?

I am.

Cheers
DD

 

That's what I was thinking., but the upper cooling flap is on its own linkage and I have manually closed it, and the lower flap you can feel through the air outlet and it moves as well and I have manually positioned that closed as well. Will play some more with them.

 

I think this is supposed to be full heat flap positions and the air from the top side and feet vents is cold. If hot water is felt at the heater core outlet is there only one path through the core. I don’t think there is a bypass that would allow flow but not to the heating fins of the core. I’m stretching here, I know.

 

It's been eons since I last dealt with flaps, linkages, and associated adjustments. I'll have to do some mulling.

There have been cases where the flaps were broken inside the case. Not common, but possible. Not a pleasant thought nor easy fix. I mention it at the moment merely so you'll be relieved when the problem turns out to be something much less ugly.

Cheers
DD

 

4 components to check and/or replace:

1) thermostat
2) heater valve
3) Ranco rhermostat at core
4) possibly the Amplifier, but first check the black wire Fuse at the amplifier multi-wire connector.

 

Hi - All these posts are super relevant since I just started my journey into the Delanair/climate/AC evaluation. Hope you don't mind me piggy backing a question on this thread.

My 86 SIII climate control seems to be fairly healthy as far as servo and amp since defrost, full cold and mix scenarios all move the vent flaps / blowers / heat level properly, if perhaps not fully sealed..... but I can accept that after 34 years. I have yet to evaluate the AC compressor and those bits, but as far as heat/defrost things seem good enough.

My main question regards my servo behavior. If I have things set to max cold, then turn on the system to AUTO, then switch to some mid to high heat.... she whizzes, whirs, pops and clicks and eventually stops making noise and the air starts blowing from the side dash vents and a from the floor vents.

But the "eventually" above is my question... it can chatter away for several minutes before it seems to settle down. Is that normal? Is all that manual servo operation and flap rod movement and vacuum redirection supposed to take that long to execute? Or.. is this lengthy period to quiescence a symptom of something problematic.

Thanks and keep the debug details coming!!

Randy

 

Just a few pointers:
One of the most likely causes of your symptoms is a failing aircon amplifier together with a failing servo. There is a rheostat on the servo that is driven by inputs from the amplifier and causes the servo to move the rods, this is a known failure point. Gary at JagAire has all the required bits to fix these two. i would be surprised if this did not cure it. However, read on!
The engine must be fully warmed up before you test anything on the aircon unit
Full cold shuts off the hot water valve in the engine bay (on the XJS in the engine bay anyway). This is achieved by a vacuum being applied to the hot water valve from a vacuum thingy on the unit in the cabin. Check that the vac lines to the heater tap are intact, not leaking etc.
There is a vacuum reservoir somewhere (in the XJS under a panel in the engine bay where the pedal box would be, if the steering wheel was on the opposite side). The vac line to this from the inlet manifold may have failed, the vac reservoir itself may be leaking, or more likely still the non-return valve in the vac line to the reservoir from the manifold may have failed/jammed etc etc.
If all this test out Ok and seems good, then the first suggestion is even more strongly likely.
Finally, there are various small bore plastic vac lines all over the unit, these can become detached from their spigots and the vac actuators they go to may fail.
The attached may be useful

 

Thanks Greg!! Great info and I am a glutton for large PDF docs with this level of detail

I just redid my vac lines in engine bay and will re-check. But at the time of that research I convinced my self that the one way valve to the AC vacuum reservoir was only really relevant when the motor was not running and producing vacuum. I had believed the point of the reservoir was to provide a temporary vacuum source in lieu of running engine vacuum.

But anyway, have lots of comonents to check as I continue educating myself and understanding how this colossus works!

Randy

 

Not normal.

Normal would be a few moments to perhaps 30 seconds. Not that I've actually timed it with my watch, mind you. But "minutes" is certainly not the norm

Cheers
DD

 

The one-way valve is there to ensure the vacuum in the system does not disappear at wider throttle openings and also that a steady "level of vac" is maintained. As Doug said, the long intervals of messing around are not normal, which is why my money is on the Amp and Servo, providing the vac sources are A1. What happens is that the duff rheostat on the servo keeps giving incorrect changing signals to the flaps, and the amp, if working, keeps adjusting to the fluctuating inputs it is receiving from the system as a result of the constantly incorrectly changing servo etc etc etc. Eventually the servo rheostat starts to get a decent spot and the thing clams down. But all this can just as easily be caused by the amp providing funny signals to the servo.
JagAire have a relatively easy test to do explained on their site to test the servo rheostat.

 

According to the Service Manual, the servo takes 20 seconds to go from full cold to full hot.

Jeff