Some while ago I posted about a how to diagnose the lack of function of blowers for the climate control. Turns out I was full of ****. It's non-functional again.

I replaced all the microswitches but it hasn't solved the problem.

Here's what I've done so far and some observations on testing.

I've isolated the problem to something after the microswitches and before the relay. Relay is not getting power, and I know this from testing.

Power is coming into the climate control switch. Climate control switch is working properly. I have tested and retested and replaced all the microswitches with brand new. All old and the new microswitches tested fine on bench testing.

Now, when I plug the green wire into the correct miscroswitch terminal I get power. With no other wires plugged in I get full power on each of the other terminals of that microswitch when the switch is set for its respective position. As soon as I plug any wire in to a terminal with the correct power setting (in other words discount that I have the selector misconfigured), the power disappears.

So, in normal operation the green wire brings power and the pink goes to ground with the switch in the "Off" position. With the climate control switch turned "On" (that is to say to Lo, High, Defrost or Auto) the Brown wire takes power from that microswitch to the next microswitch.

In my case whenever I plug in any wire to any terminal (the pink one or the brown one) on that microswitch, Power goes from 12V to .0007 volts. I thought it might be a bad resistor, but it does it for all wires even ones that aren't on the resistor'd line. As soon as you touch ANY wire to the terminal the power that was there a millisecond ago is gone.

I'm thinking a bad ground but don't know enough electrics to say for sure whether that would account for the problem. Any ideas?

Again, the problem is definitely between the switch and the relays and having something to do with those wires in the harness that service the microswitches.

 

Rule Number One of Jaguar Electrics. Always clean grounds.

I pulled the dash apart further to get to Ground # 7 which is behind the glove box and which grounds basically all the climate controls. Looked pretty clean and couldn't imagine how it couldn't be a good ground, but cleaned the ground wire loops with some 400 grit sandpaper along with the lockwasher, coated them all with dielectric grease and tested again. Guess what........

Never forget rule number 1.

 

Actually, cleaning the grounds is rule #2. Rule #1 is to replace the fuse! I am glad you found the problem but the most common cause of the blowers not coming on is...the 50A fuse! These glass fuses can work intermittently, test as good, and still not supply the power needed. Many years ago when this same thing happened in one of my xj6 cars my Jaguar specialist diagnosed this over the phone as the fuse. It was the fuse. The procedure: Remove the fuse, tighten the cradle, fit new fuse.

 

Lol. That's true. I did check that first and replaced it just to be sure!