NO Climate FANS (1983 XJ6)

The fans for the climate control in my 83 XJ6 suddenly stopped blowing this morning while driving. I was thinking it was one of the fuses, but all 4 fuses (50 amp fans, 15 amp for the amplifer as well as the other two) were fine. Using my volt meter, I have 12.8 volts at both sides of the 50 amp fan fuse , BUT I am NOT getting any voltage on the brown/white wire at the resister relay pack. I ran an aux.12 volt wire to the brown/white wire, but the fans still did not come on (using the console mode switch). IF I touch the green/slate wire to the brown/white wire while suppling “my” voltage, the fans run fine. At least, I know the fans are good! Also, I have no power on the brown wire to the amplifier.

I replaced the resister pack, amp and servo with no joy. I should have known these would not work if there was no power on the brown/white wire. But, I am totally confused because the system still will not work when I supply “my” power to the brown/white wire.

After reading hundreds of post and a day of pure frustration, I am gave up!

Any help tremendously appreciated! I’m at a lost of what to do next!

Richard

On one of the heater pipes, roughly above the throttle pedal, is a temp switch. Remove the wires and jump them together. See if anything changes

(An alternate, but not necessarily easier, way of doing these in jump the two test leads in the console together. They’re roughly behind the LH footwell outlet. See pic below)

If this switch is stuck in the open position the fans will not work

Cheers
DD

Richard,
Do the fans work when the mode selector switch is rotated all the way to the Defrost/Demist position?

Paul

Doug…Just joined the 2 test leads together. No joy. Paul…The fans do not work in any of the mode selections (including defrost).

In fact, I hear absolutely nothing when I turn to any of the mode selections (low, auto, high and defrost)! I do not hear any “clicks” in the system. The fans and entire system is dead.

I just rechecked all the fuses. They are good (showing 12.8 on the 50Amp fan fuse)!

Richard

Richard,
Inspect your fuse boxes for melted plastic. I had a heater blower motor problem in my 1990 V12 VdP a couple of years ago when the fuse panel plastic melted and deformed so that the fuse wouldn’t carry current. The attached picture show the details. I believe that I posted about this at the time. I had to remove and replace the fuse box one wire at a time. My car has the Delanair MK III which is slightly different than the Delanair MK II in your car, but the melted fuse panel resulted in failure of the blower motor.

Paul

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Paul,

I am getting 12.8 volts at the top and bottom of the 50 AMP fuse. Are you saying I could still have a wiring problem behind the fuse holder?

I am still mystified the fans stoppped suddenly while driving which sounds like a fuse, but they are good???

Richard

One of the three big Problems with that fuse holder is that the 4 contacts that all touch the fuse are connected individually, so you need to check both clamps at both sides of the fuse (only the output side really, but I don’t know which that is so I used to verify all four) for power (and not just voltage)

In Pauls example photo you can see that only the bottom right one got hot, the left side might have had nothing to do with the circuit at all, I hope you understand what I‘m trying to say.

Did you run the jump wire from the car battery source, Richard?

The brown/white is the general power supply to the fans via the relay pack - and with adequate power; the fans should operate normally.

As Paul (and David) says; the lack of power on brown/white may be disconnection at the fuse box. The fuse may show 12V at both ends, but the wire may have detached from the fuse box due to overheating. However, with battery power on brown/white at the relay ‘everything’ should be normal, but as Doug says - if the system is in ‘heat’ mode the, the fans will not operate until coolant temp is above 41C. However the fans should still run in ‘def’ position…

At the relay bank; green/slate bypasses the resistor pack - but the other fan speeds will be affected if the resistor pack has failed. Ie, controlled by the respective relays yellow, blue and red should show power when respective relays are activated…

This is related to the coolant temp switch - but exactly what this means is uncertain. If the fans stopped while driving in ‘auto’; it may be pertinent - but whether the brown is an amplifier ‘input’ or ‘output’ is unclear. Check both sides of the connector?

You may have more than one fault, which complicate matters - but restoring power to *brown white is a first step…

Frank
xj6 85 Sov Europe (UK/NZ)

Richard,

one point David wanted to make (I think!) is that you might start to exclude the fuse as a culprit by using a simple and cheap test light instead of the DVM. It only needs minimal circuit to measure voltage with a DVM, but resistance may increase immediately once power - as required by the test light - is transferred and thus reveal a defective circuit.

Good luck

Jochen

75 XJ6L 4.2 auto (UK spec)

David/ Jochen…I will again check the fuse 50 AMP holder/wires. I understand what you said which I did not realize! I used a test light with a display that gives the volts as well.

Frank…I ran a wire from the positive post on the car’s battery to the brown/white post on the relay pack, BUT no fans or anything from the system when using the mode switch. It was then I got confused!

Richard

Actually no, i meant that the fuse touches four bits of metal and you would think two and two would be connected. Not necessarily.

Test light is the best and simplest way for troubleshooting.
if the relays have power and still no clicks nothing is switching them on right?

It’s very odd that there is then no fan action in any function switch position, Richard; the ‘Hi’ bypasses the resistor pack - and the ‘Def’ should bypass the coolant temp switch…

The latter is easily bypassed by connecting the two wires (on the switch) together. The relays switches brown/white to yellow (‘Lo’), blue and red (servo controlled) and green/slate (‘Hi’/‘Def’). This can be used for voltage checks to verify relay failures - requiring verified switch functions on relay coil inputs…:slight_smile:

You should also verify servo function the usual way, since you have changed(?) it. I sort of suspect a double fault due to the ‘fiddle factor’…

But the first, and simplest, is to get proper power on brown/white.

Frank
xj6 85 Sov Europe (UK/NZ)

Frank…I now have 12.8 volts on the brown/white wire at the relay pack, BUT nothing from the mode switch from any of the settings, including “defrost”! I looked at the wiring diagram. There seems to be a light green >green wire that feeds power to the mode switch itself from a fuse 6. If that be true, could that be the reason the mode switch is “dead”? The fuse 6 is suppose to be in the main fuse box (according to the diagram).

I am away from the car and can’t check it until next week.

Richard

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[quote=“Richard_Greene, post:13, topic:448191, full:true”]
…There seems to be a light green >green wire that feeds power to the mode switch itself from a fuse 6. If that be true, could that be the reason the mode switch is “dead”? The fuse 6 is suppose to be in the main fuse box
[/quote)

The green wire does indeed feed power to the function switch from the 15A fuse, Richard - without power the system behaves as it is ‘off’…

The 83 model year was a transition year, and in the earlier version the AC fuse was in the aux fuse box (on glove box lid) - #13. You should certainly check that!

The finer details of the AC operation is convoluted to say the least - but the need for power to the function switch is undeniable and a first checkpoint now…

Frank
xj6 85 Sov Europe UK/NZ)

Yes I had melting in the fuse box recently exactly like that on that fuse as well. I just cut it out and replaced it with a little blade fuse box.

I had trouble with one of the headlights cutting out which seemed to be fuse holder not making good connection to the wiring in the identical engine bay fuse box so I’ve replaced that as well. See if wiggling the fuse with it turned on does anything.

I removed the mode switch today. I had no power coming to the green wire which powers the switch even though the fuse was fine with 12.4 volts on both ends (of the fuse). I ran a positive wire to the switch (where the green wire attaches). I also ran a ground wire to the black wires on the switch. There was still no fans! I then bridged the green and brown wire on the switch, and the fans blew on defrost, but there was no fans or any movement from the system on any of the other mode selections. Does this suggest the mode switch is bad?

I am still not understanding why there was no power on the green wire when the fuse was good.

Richard

Previous message did not include my edit!

I removed the mode switch today. I had no power coming to the green wire which powers the switch even though the fuse was fine with 12.4 volts on both ends (of the fuse). I ran a positive wire to the switch (where the green wire attaches). I also ran a ground wire to the black wires on the switch. There was still no fans! I then bridged the green and brown wire on the switch, and the fans blew on defrost, but there was no fans or any movement from the system on any of the other mode selections. Does this suggest the mode switch is bad?

I am still not understanding why there was no power on the green wire when the fuse was good.

Richard

Check for power on the brown and the pink wires, Richard - the only purpose of the switch is to change between the two…

As there is no change when jumpwiring power to green; the likely cause is indeed a switch fault. To test further; jumpwire power to brown or pink - and see what happens? It should be fairly easy to change the microswitch, but also: the microswitches ar activated by the function switch’s shaped channels - so check that channels are intact and move the switches as they should…

The ‘def’ is sort of on a different circuit; it connects to ground - and will blow a fuse if directly connected to power. The various microswitches performs an intricate, coordinated connection dance when function switch is turned - part of the intricacies of AC operation…

The lack of power on green at the function switch may be a reason a PO changed the connection to the 50A fuse - then something else happened…

Step by step; I ‘think’, with power jumped to brown, that the system may work normally. If so; the microswitch, or its switching is faulty - to be rectified. You then need to trace the green wire from the fuse to the function control - to ensure that a; if it is the right wire at both ends. A crude test is to remove the fuse and ohm the wire between fuse holder and the function switch end. Or b; that the green wire is properly connected to the fuse holder. Or c; where the break is - and eventually replace the wire.

If the system, with the jump installed as described still fails to operate properly - we are in unknown territory! Either related to connections made during refurbishing the AC - or a malfunctioning function switch…or something else to be pursued…:slight_smile:

Frank
xj6 85 Sov Europe (UK/NZ)

Thank you, Frank! I sincerely appreciate your time! I will hopefully get back to the car next week! I create stress! I take delivery tomorrow on possibly another headache, a Rolls Royce Corniche!

Richard

[quote=“Richard_Greene, post:19, topic:448191, full:true”]
I will hopefully get back to the car next week!

If you apply jump wires, Richard; do not connect ‘raw’ jumps without an inline fuse - jumps bypass circuit fuse and is unsafe. In this case, when testing functions; jumpwire from green fuse to brown on the function control.

And I would not really mind the possible headaches of a Rolls Royce…:))

Frank
xj6 85 Sov Europe (UK/NZ)