1985 XJ6 Vanden Plas


blower motors stopped running all of a sudden, I have been reading all the posts I can find and trying to trouble shoot, so far I have checked the following

checked all fuses, 2 in fuse box have battery voltage, behind the left side of the console, and the right side, all ok

removed green/slate wire from the relay applied battery power, blowers both run

the screw on main lead on the relay has battery voltage

relay showed signs of corrosion on some terminals, replaced relay and cleaned connections

removed and connect the two wires on the heater core temp sensor, no change

the defroster flap still worked

while checking voltage on the brown, brown/yellow in fuse on the right side of the console and turning the fan switch, at off no voltage, when on only .6 volts while testing this the defroster flap stopped moving

does any one know what the voltage should be on the rt side inline fuse?

I'm thinking the switch maybe bad, if it is would it shut down the whole system?

thank you for any ideas you may have

 

no easy solutions, it takes checks and more checks...and substituting parts.

1) easy check: substitute the large relay with another, (there are 4 relays inside it), (Number 2 in diagram below) > be very careful when removing and reconnecting the wires, it is critical they are correctly connected, disconnect battery before.

2) check the blower Resistor mounted to the side of the a/c case and above the large relay. If the "springs" look burned, it probably is bad. (Number 3 in diagram).

 

thank you, didn't check the resistor, will do that, but still looking for what the voltage should be on the right side in line fuse.

 

forgot to say I ready replaced the relay

 

Looking at the diagram I'd say it should be 12v.

Cheers
DD

 

OK, good. Now you know everything downstream of the relay pack is OK




Good, That sounds like supply voltage to the load side of the relays




good.

It sounds like you are lacking *control voltage* to the relays.

With the mode switch set to 'auto", slowly operate the temp control. Do you hear the servo whirring?




Try bypassing the Ranco thermostat in the same manner and see if anything changes. Just follow the brown wires from the inline fuse you were asking about. The Ranco thermo is just a few inches above




I think it would, yes.....thus the question about the servo whirring



Cheers
DD

 

My problem with intermittent or no fans turned out to be, after many hours of study and trouble shooting, was the mode switch. Pain to replace but fixed my problem. There are 4 microswiitches inside it and they do go bad.

 

The mode switch rarely fails....but, thanks to you, we're reminded that 'rarely fails' isn't the same as 'never fails' !


Cheers
DD

 

Thank you all for the suggestions, will try these ides and follow up when done.

 

We did some more troubleshooting, jumped 12v to the brown / yellow wire on the relay, the fans work, change speeds, set to auto, moving temp control fan speeds change. So it must be the mode switch. Removed most of the center stack, but can't get the switch out. Picture of where we are disassembled to. Any ideas would be helpful.

 

see if this helps

 

You have to remove the entire center console first for access.!! A pain but doable. Also remove hrs air vent(4 screws).Then you have to remove the 10 wires from the switch from side of mode switch. Make a diagram where they go. Then remove the 2 blackvacuum lines from vacuum switch attached to side of mode switch.
Then remove screws holding the switch in place from the front and maneuver the switch out of radio opening.

May have missed something but did mine 6 months ago and memory fades. All can be done in a day but I took 2.

My switch had one bad microswitch out of the four. The microswitch which the green wire attaches to was bad and not sending power to the remaining microswiitches . This microswitch sends power to the remaining 3 microswitches. This one must work or the system is dead.

 

Here what you need to see and access

 

And here it is

 

If you need a test switch to substitute, I can send you the one pictured. New ones are well over $300 if you can find them. I bought the last NOS one still in the box in the country I think to keep as a backup if needed and was expensive. David Boger probably has a good one, but test anyone you get before putting all the stuff back together. Just hook up all 10 wires to switch and leave it outside the panel.

 

Thank you for your response, and pictures. Finished taking the console out, got to the switch found three disconnected wires, have no idea how it happened I have not done anything to the car even near that area. Reconnected the wires and it all works. I guess 30 years and 110,000mi
they just fell off, tightened all connections and retested during each step of reassembly. The pictures Saemetric sent were just what we needed though. while trying to remove the switch we removed the two screws which hold the bracket for the defroster vacuum switch, we couldn't figure how to attach it because the bracket fell into the wires below. Thank you again without the picture we never would have figured it out.

 

amazing, 3 disconnected wires.

 

We might have disconnected some while removing the switch, but as soon as they were reconnected everything worked. Drove the car the last two days and its all good. Thank you all for your helpful trouble shooting tips.