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Getting the climate control fired up on my LS-swapped '86 XJ6.
I have a new amplifier (thank you, @Andy T. !), and blowers work. When I turn the control knobs I get the expected readings to the Amplifier. I have also checked fuses (main/secondary boxes, as well as the ones I could see in the vent plates). At some point in the car's life someone did some creative wiring with fans that may have misplaced some things, so I'm keeping an eye out for that as well.
Current issues:
1) the servo doesn't function (no noise when switching from hot to cold + air blows out of all vents regardless of temp settings)
2) I don't have a 12v+ signal from the Green/Brown compressor wire.
Question: Could a bad servo also prevent the compressor from firing on? It looks like there are some wire connections in common, but I'm not confident in my diagram literacy to say if a bad servo could cause no signal to the compressor.
I don't think the servo has any authority over the compressor clutch circuit. In fact the compressor is designed to be operating in all climate control modes so there's no reason for the servo to control the compressor circuit.
The Ranco thermostat-switch is one area to look. If it is stuck in the open position then the wire to the compressor will not have power. With a test light look for voltage in and out of the thermostat.
But.....
If I understand correctly your servo is not operating. An easy stepping-off point here would be the water temp switch on the heater pipe. Bypass the switch and see if the system comes to life. If you remove the console LH cheek panel you'll see two dangling wires to facilitate these. These are the wires marked "test" in the diagram.
Lastly, is the 3-prong thermal limiter fuse at the compressor still in existence, connected, and not blown?
Couple of things -
1) where is the Ranco switch located?
2) What/Where is the water temp switch? The first thing that comes to mind is the one-wire coolant sensor in the block, but I assume that's not what you mean?
No 3-prong limiter. It's an engine swap with a new compressor. I'm looking for + voltage from the Green/Brown wire to connect into the new compressor, and I'm not getting any signal off that wire.
Figured out the Compressor! Previous owner apparently wired a console switch that turns the compressor on and off. Not the worst mod I suppose, but one of those things that's tricky to figure out 2-3 owners later. Now on to the servo. From a troubleshooting perspective, all I've really done is checked fuses and turned the temp from low to high and back while listening. Any other conditions to check or be aware of before I replace? Also, any guides on how to replace?
I think from your first post that you are seeing the expected voltages from amp to servo but that the servo fails to move?
A fairly common fault is dry solder joints on the diodes that are in the wiring of the servo.
To access them, you need to get the servo out (actually not too terrible a task) and unwrap the insulation tape on the feed wires. Some of the diodes depicted in the wiring diagram are hidden on little boards inside there and they can develop bad contacts which can be rectified by re-soldering.
Two questions:
1) for the test leads on the water temp switch, does one lead switch the servo all the way to “cold” and one all the way to “hot” when + is applied?
2) is there any time delay on the servo, like car has to be warmed up or similar?
Two questions:
1) for the test leads on the water temp switch, does one lead switch the servo all the way to “cold” and one all the way to “hot” when + is applied?
No.
When you jump the wires together you're bypassing the water temp switch. That's all.
Driving the servo motor is done at the servo connector on the red and purple wires. We'll cross that bridge if we get to it
2) is there any time delay on the servo, like car has to be warmed up or similar?
Yes, and that's where bypassing the temp switch comes in.
If heating is called for the temp switch keeps the system shut down until the water temp is hot enough to actually provide some heat. This way you're getting cold air blowing into the cabin when you're trying to get warm!
If the temp switch is faulty (stuck "open") the system just won't operate. Normally this non-operational mode includes the fans but you said the fan circuits have been changed in some way.
In any case is a very simple check that only takes a couple minutes. Worth trying it just to see if anything changes.
Thanks, again- Doug! I appreciate the patient explanations.
I’m unable to locate those two leads so far,
and it does look like there has been a fair amount of aftermarket work done.
I think I will try jumping the servo next.
+ voltage to the red and purple wires at the servo connection (RH cheek) should make it move, right? If that works, then worst case could I wire a switch to flip it between hot and cold? I don’t love the idea but I like it more than tracing wires
Case closed on this, for now at least. I pulled the RH cheek and tested the Servo per the directions on Jag-aire (thanks, @Greg in France !). It appeared to function as expected. When I plugged the connector to the amp back in, it seemed to switch back and forth without issue. Unsure if I just didn't hear it before, or if I jiggled some connectors, but in any case I appear to have heat now, and will hopefully have AC once we get the hoses installed and system charged next week.
Diagnose Climate Control ('86 SIII)
