OK, I'm a little stumped here. I'd assumed since I bought my '85 V12 (Delanair II) the heater valve was kaput so I went outside today (19 degrees here) to play with the old one while I waited for the new one to come in.

I have read through Kirby's book and I feel like I have everything I need to fix the issue...except where to actually begin. Electric? Vac? etc. I'll post here a rundown of what I have going on and hopefully someone can chime in and give me a starting point.

First, two pictures. At some point a previous owner added this switch to the panel in the passenger's footwell that also holds the fusebox cover. The two wires on the switch seem to jumper a factory connector that has TWO yellow wires with brown stripes on it. This connector seems pulled off a relay up under the dash (not real sure what it is, I can barely see it, but it's in the pics) and the switch jumpers out that terminal. I ASSume at some point something upstream of this lead failed and send constant 12v to the relay(?) and rather than fix it, the owner decided to put this switch in. However in neither position the switch doesn't really seem to do anything (at least, it doesn't provide me with heat). Thoughts? Two pics attached. FYI the two black wires go to the switch, you can clearly see the connector with the YL/BRO leads and hopefully you can see the relay (?) up under the dash.





I tried following Kirby's writeup and a couple others I found by searching here and it got me nowhere, so I'll let you all know what I have done and the results I got, and hopefully someone can point me to the next step:

1. Heater valve is operating. Anytime the system is on, the valve is open - I verified this by disconnecting and running a garden hose through it. I have also tried running the system with the vac hose to the heater valve removed and plugged just to be sure. Vac on: valve arm up (linkage down). Pull vac line and arm immediately drops (linkage goes up). Also FYI, it seems like the heater core is OK - the windshield is covered in moisture (need to continually wipe with paper towels) but I do not seem to have any coolant leaks, the condensation does not taste like antifreeze, and I have cleaned out my evaporator condensate drains and found no moisture sitting in the evaporator.

2. Vac check valve under hood is operating correctly.

NOTE: all tests are performed with temp knob on 85 and the slider all the way to the red arrow. I do not suspect the temp knob (yet) because when I go to cold the AC clutch does engage and the AC works. At least, when it's not 19 degrees outside.

Fan knob:
Low - blowing out of all vents (foot-console side-def-center dash-outer dash) - fan is on low.
Auto - blowing out of all vents but outer dash seems somewhat decreased - fan always on high.
High - same as Auto
Def - I can hear a flap move but seem to have the same results from the vents.

Another note: I pulled the 50A blower motor fuse from the driver's footwell fuse panel to try to hear what motors/flaps were moving when, and the fan continued to run as indicated above, so it was really hard to tell if anything was moving when it should be.

Anyone have any ideas what my next steps should be? I definitely want to get rid of this switch and actually fix what was wrong before, but what's really critical for right now is getting some heat on.

Thanks,
Darel

 

Oops...dieregard about the fan still blowing with the fuse pulled...accidentally pulled wiper fuse instead. I hear a flap move for a very short period of time when switched into Def but no real movement otherwise. I did disconnect the vac line off the heater valve and heard coolant start to circulate through the valve but nothing ever got hot. I can see now that not only is something keeping the coolant valve shut off all the time (always has vac going to it) but maybe the heater flap is not operating? But then it doesn't really seem like any flaps are operating correctly so there must be some underlying cause.

 

Another bit of info...at no time in any mode of operation did either of the pushrods move on the side of the unit. So, it almost seems as though I have no control power - is this a bad servo? Is there a fuse for this? I noticed an inline fuse attached to the side of the case, but I'll be damned if I can get it off with non-pozidriv screwdrivers, so I'll have tro order in some of those.

 

There are 2 fans and 2 fuses one in each side fuse box under the dash.

I would start by cleaning ALL of the connectors associated with the AC, the Jag is notorious for bad connections especially in the AC box area. The AC or windscreen leaks and corrodes all of the connections including the grounds. I have cleaned mine and it still does not work correctly.

You can buy electrical contact cleaner in a spray can and a cotton bud or pipe cleaner for the larger connectors and the smaller ones spray them and work the plug in and out a few times.

give this a try and report back

cheers
Warren

 

Thanks Warren,
Where am I going for "all" the connectors? Just pull off all the underdash trim pieces and start taking stuff apart and cleaning it? Are there any hidden ones I'm going to miss doing that?

I do have a wet floor, this is definitely a possibility.

It really seems as though there is no control function to anything but the fans...but then, I have high speed even when the heater core is cold, I thought the little temp sensor was supposed to keep the fans from going into high until the engine was warm?

Thanks,
D

 

The switch on the yellow/brown wires looks like a (common) owner mod to cut off the compressor while leaving the rest of the system operational. It's sometimes called a "fresh air" mod.

The system is designed to cool all incoming air first and then heat it as needed. The a/c compressor operates in ALL modes, even when heat is called for, to dehumidify the air. The fresh air modification eliminates that operating feature...so incoming air will be ambient temp and not dehumidified. Still, though, the flaps in the climate control case have to be in the right position to direct air thru the heater core for heat.

I may have asked this before but do you hear a faint whirring noise when you change the temp setting? It's a slight sound so try listening for it with the key on, engine off. If you hear the whir...which is the servo motor operating...then you know that the system is (at least) fundamentally operational and trying to follow "commands".

Cheers
DD

 

If heat is called for, and the system *recognizes* that heat is called for, the temp switch on the inlet pipe of the heater will prevent the fans from blowing at *any* speed until the coolant warms up.

The switch is sometimes bypassed.

An exception is if "Def" is selected....which defeats all the automatic functions

Cheers
DD

 

You should have four fuses: the one you just mentioned above, one on the ground wire from the amplifier, and two more in the regular fuse boxes. I can't remember the fuse numbers for the ones in the fuse boxes.

Door you have the wiring schematic for your year/model?

Cheers
DD

 

Amen, brother Warren, on the corroded connections :-)

Cheers
DD

 

*IF* all the fuses are OK and *IF* you don't hear a whirring noise when you select a differerent temperature you probably have a dead amplifier. It's a fairly common failure point.

There are numerous tests that can be made but without a "known good" amplifier the test results can be skewed.

Problem is, the amp is about $250-$300 so it's not a cheap guess. It's a good guess, but not a cheap guess :-)

Cheers
DD

 

Guys,
Thanks for your help. Here is some more info:

- Fan fuse pulled, and I have all the underdash trim pieces removed, so I ought to be able to hear the servo. I hear nothing when I change the temp knob.

- Took apart all the electrical connectors I could find WITHOUT tearing into the dash (i.e. didn't pull apart temp selector knob, etc). Surprisingly everything under the trim panels was clean, dry, and not corroded. I shot what I could find with contact cleaner anyway. No change to operation.

- Found all four fuses. All good.

- Sounds like the switch may be something I want to leave in place. Don't need to have the compressor running constantly. For now, just to try and get everything back to square one, I put the wiring back the way it was factory.

- The ONLY time I hear any response to control input is when I switch to Def I can hear some sort of electrical motor move, very briefly. Is there some flap in the Def system that has an electric servo? There seems to be no change to the airflow but I am fairly sure I can hear something move, or try to, very briefly. Actually it sounds more like a relay engaging.

So, this leaves us at a dead amplifier? Not the end of the world - I have a parts car. I don't know if the amplifier in the parts car is working or not, but it could save me a couple hundred bucks. Where is it located and how do I go about changing it? I found the fuse in the amplifier ground wire, but that wire and the associated bundle with it goes back into some dark, scary places under the dash. Any tips for R&Ring it?

There's a small blue adjustment dial next to where the bundle of wires goes into the amp - any chance fiddling with that will get me anywhere?

Any way to bench test the amplifier from the parts car to see if it's good before I install it in the good car?

Thank you guys for all your help!

Darel

 

Went down today to pull the amp out of the parts car, and lo and behold it had already been pilfered at some point. Dammit.

Before I drop $200 on a lipstick amp, I'd like SOME way of feeling better that this is actually the problem, especially since I've owned the car for one week and already dropped almost $500 in parts alone.

Is there any test you can do on the amp? If I were to start the car, and disconnect the big round plug to the amp, what would the system do if it is operating normally (i.e. what flaps fail open, would the fans run, etc.).

I've already tried moving the two pushrods in a vain effort to manually get heat into the cabin. Will I be able to force them open, without changing any adjustments or taking anything apart, with the amp powered down?

Thanks for all your help. Just need a warm fuzzy before dropping $200.

D

 

All,
I'm not entirely convinced the amp is the problem here. I'm wondering if the servo it controls is not frozen up? Just want to run this by you before I drop $200 on an amp I may not need:

Did a little bit more poking around yesterday. When I switch the system to DEF, the vac dashpot next to the driver's right foot does move - full range of motion. Is this controlled by the servo or straight off a microswitch on the selector knob?

Also, I ran the system with the wiring harness to the amp unplugged yesterday. There was no change at all to the way it is behaving.

Finally, I cannot move the two main pushrods, no matter what I do. Car off - will not budge. Vac lines disconnected - will not budge. Car on, amp unplugged - same. I would think that at some point pressure (be it vacuum or electrical, whichever it is) would be relieved and I would be able to push them, even just a little bit, manually. Yes or no?

I am wondering now if it's not the amp but really a frozen up servo? Does anyone have any thoughts on this?

FYI I still have exactly the same reaction from the blower fans too - in any fan position, and regardless of whether the car is warm or cold, they are on high, except when physically put into LOW, then they blow on low. AUTO-HIGH-DEF they blow full blast. Maybe this is the amp, then?

I also want to say thanks to you all for helping me out - I am in a position to have to do some major surgery to my dash and interior as well as shell out a lot of money, and I'm really hoping to minimize both of these things. Thanks for all the help.

So what do you think - servo or amp?

Darel

 

Unplug the servo. Find the red wire and the purple wire.

Apply 12v to the red wire and apply ground to the purple wire. The servo shoud rotate in one direction. Reverse the polarity and the servo should reverse direction. If nothing happens the servo is day-ed.

Whatever you do, don't let the servo keep running during this test. It will over-rotate and damage the switches. Just test long enough to determine the servo motor works...a second or two in each direction.

Servos seldom fail....but "seldom" isn't the same as "never"....so it's worth a quick test :-).

If you have to replace the servo you'll have a chance to observe what a brilliantly complicated bit of engineering they are :-).

Cheers
DD

 

Perfect, this is exactly what I need. Thanks Doug!

I'll test it out when I get my alt back in and hooked up.

 

I can also see what a brilliantly expensive piece of engineering they are....

 

UPDATE:

Looking for one last confirmathion it's a dead amp.

I actually managed to find the amp from my parts car in a box the PO gave me. I just plug-and-played and the system behaved EXACTLY the same way as the other amp.

I played around with my meter and some very creative temporary wiring, and did get the servo working, both directions (12v to red and purple) so it's not the servo.

From BOTH amplifiers I am getting a constant 12v from the red feed and a constant 0v from the purple.

I'm confident I ruled out the servo, which is great. However, I find it very hard to believe that both amplifiers have failed in EXACTLY the same way, i.e. both are sending a constant 12v to red.

I unplugged both ends of the cable and there are no shorts, so the 12v is definitely coming from the amp.

However, why? Am I going to drop $200 on a replacement amp only tro have it burn up in the same way, because I'm just missing a different problem here? The inline fuse in the grounmd is intact, so I doubt a short is the problem.

Is it possible the amps are receiving a signal from somewhere that drives them to full 12v-to-red (full cool, I believe) and they are actually OK? I have the Delanair factory service manual (which is awesome, by the way) and it only lists the resistance on the temp control switch as 10K ohms - which temp is 0 ohms and which is 10K? Also, I'm not real convinced this would prevent the linkages from actuating the flaps also.

Or is this definitely two bad amps?

Thanks all for the help. I can't wait to get this tracked down. At the very least, using my crude jumpers I managed to get the system into full defrost and "hot air" mode and then left the servo unplugged - this gives me at least the most "useful" configuration and I can still operate the system to off and DEF on the control knob.

 

did you try flushing the heater core?

 

Yes, flushed core last week (green as a whistle) and bled system yesterday, hot pipes on both sides of heater valve. Either way the servo is not responding so it's not in the core or valve or the core temp sensor.

 

The failure rate on amps is fairly high. I wouldn't fall over with surprise at having two with the same fault.

Wish I could offer something additional to make things 100% certain but I'm tapped out of ideas at the moment :-)

Good luck

Cheers
DD