You have two choices to test the thermal fuse. It is actually on the underside of the circuit board on the opposite side of the flat metal spades.
You will need an electrical multi test meter set to test continuity. The thermal fuse is actually soldered to two of the three round metal soldered joints shown on the far right hand side of your picture. They in turn are connected to the two larger flat spades through tracks on the circuit board. If you set the meter to continuity and test the two spades and there is none, then the fuse has failed. You can also test the soldered joints (from memory I think it is the outer two).
To actually get at the fuse, you need to gently pry the black plastic clips that keep the green circuity board held in place and it will lift out. Then the fuse will be evident. Before you can pry out the circuit board however, you must desolder those three joints on the right hand side since the fuse is held in place with a small bracket underneath.
To remove it, you heat up the soldered joints and use a desolderer to suck out the molten solder from around the fuse wires. The circuit board can then be lifted up, you unscrew the small metal fuse bracket, and remove the failed fuse. Pop in the new fuse, screw it back into place (there is some white grease around the bracket which you can just re-use) and slot the board back down over the exposed fuse wire legs. The wire legs of the fuse will inevitably extend quite a way out from the circuit board once it is soldered and you just clip off the excess wire with some scissors (or wire cutters).
Depending on whether you send the complete unit back, you can make this repair to your old thermal fuse module and just keep it on the shelf in case the a/c dumps water on it and shorts it again in the future.

 

Digband, sometimes when water drops onto the blower motor, it doesn't break it but it can cause the blower motor shaft to rust and seize into its lower bearing, particularly if the car is left over the winter and not used. In that case, just unscrew the 3-4 screws in the blower motor and give the squirrel cage a gentle rotate to free it up. It may squeak a bit afterwards depending on how bad it corroded, but this can be fixed by adding a little grease to the end of the shaft/bearing. I think that if the motor shaft has seized, it will probably blow the new thermal fuse pretty quickly due to excessive resitance, so try to test your new fuse module for continuity too (per the above) just in case it has already blown due to the seized blower motor.

 

LosRubios - I had the same thought yesterday and borrowed my pal's multimeter - I'm no electrician but it looks like it has current when connecting to both points you mentioned so perhaps it hasn't gone bad - see below. Much thanks for the tip about kick-starting the blower manually with a twist - gonna go try that right now - will, advise.

 

So the blower motor squirrel cage was definitely a bit stuck - I spun it a bunch manually. Reinstalled the blower and the resistor/thermal fuse module, cranked up the AC fan but still no air - nothing. Put my ear down there by the blower and while I heard a little something, it certainly didn't sound like I assume it would when working on full fan speed. Guess I wait for the new resistor part and plug that puppy in to see if it still may be the problem. LosRubios, many thanks again for all the detailed instructions.

 

Hey Digband,
Congrats on getting the car out of hibernation.
I had a similar problem with the blower motor in that it was very stiff to turn and his is what causes the fuse to blow in the control module.
I stripped my blower unit and cleaned it up like new again and used some WD40 to free the end of the shaft where it sits into the bottom casing. Never had another issue!
Enjoy your baby when you get her back out on the road,

Cheers, Andy

 

Digband, you need to set the meter to a continuity test and I think you are testing resistance. There will be a setting on the meter dial which allows the meter to emit a tone/beep when the probes are touched together and this is the setting you need to use. Basically if the two probes are connected to the ends of the fuse/two terminal spades, then it will 'beep' if the fuse is good and will be silent if it has failed.
From everything you describe, it is the thermal fuse in the module that has failed and swapping out the module will have it back up and running. The new one won't fail immediately again now you have freed up the squirrel cage. When the fuse fails, there is still a very small amount of air that comes from the vents, so this sounds exactly like what you are describing.

 

Thanks to LosRubios, GR8TBR1T and everyone else in this thread. After ordering and installing the whole resistor part from eBay, my AC system is back up and running again - for a total of about $25 dollar plus a little time and effort. A local indie garage who looked at the car last fall told me I needed a new blower motor which, with parts and labor was upwards of $500-600. I'm lucky to have found such an awesome community of helpful folks (who all drive awesome cars) - I hope to be able to give back when I can. You guys all rock. With my duckbill now opened up and lubed and AC running again, I'm glad to say this problem is once and for all resolved.

 

I hate to resurrect this after I just declared victory, but I have one last question - I have the AC working again now and the duckbill has been opened up and lubed with WD-40 silicone spray - so I cranked up the AC for awhile and let it run, hoping to see some water come out the bottom of the car, but no water coming out the bottom. Now, it's only in the 50-60 degree F range here and no humidity at this time of year, and I read that the AC condensation depends on humidity and dew point, so can I safely assume I am not seeing any drainage out through the duckbill because of the current temperature and humidity? I just want to make sure I don't have to do something like manually drain any water that may be sitting still in the "area/tube" where it should have been pouring out before I fixed the duckbill issue...? Or do I just wait till a warmer, more humid summer day to verify the proper duckbill drainage? Thanks.

 

I'd wait for results on a warmer day before becoming too alarmed yet.

 

+1

 

I agree, wait for summer but then you'll be having so much fun you'll have forgotten all about it!

Cheers, Andy

 

I had this exact same issue 3 years ago with my 07 XK and joined this forum to find a way to fix it. I used one of the pictured homemade scalpels to slice up my duckbill because mine was side mounted deep In its ”rabbit hole” and unable to be reached otherwise. I also did the WD40 to the entire fan motor assembly and dried it with compressed air to speed the process. I wish I had the amazing information provided above regarding the steps to replace the thermal fuse, I would have loved to have tried it . Absolute Brilliance!! I am writing to offer this thought regarding your current concern/ anxiety. Since you can reach it, clearly easier than I could mine, SLICE THAT SUCKER OFF! I have had no issues since slicing mine up. Each summer after I have used my A/C on the first hot humid day, I am rewarded with a glorious puddle under my car. It is a sense of Joy & Pride only those with these XK’s can appreciate. Because we share this common problem with our XK’s, we also share the PTSD of seeing that recurrent drip from the fan onto the floor mat (or our passengers feet) and relive the yoga moves involved in disassembling the fan motor and control module from up under the dashboard. That sick feeling as you see that dripping as you are driving that if you don’t get that fan motor dried quickly, you may ruin both the fan and the control module to the tune of $300 for each. When you consider the heat these XK engines make and the effect it had on the duckbill material to allow it to become stuck shut in the first place, how long will anything applied to that rubber in that environment keep it working as it should? Furthermore, any bug unfortunately enough to find itself there will burn up from the same heat. SLICE IT OFF and drive care free with the top down and A/C on if you want!

 

So I hadn't used the car for a few weeks and the blower motor had stuck from previous blocked duckbill issues and sitting without being used. As might be expected, it blew the thermal fuse in the resistor and the blower stopped working. Last time I fixed the resistor I bought a pack of 10 spare fuses, so I duly removed the blower motor and the resistor unit. I stripped down the blower motor and cleaned it up before adding some WD40 to the bearing to help is continue to spin freely.
I then replaced the fuse in the resistor and put it all back together to discover that the fan now runs on full speed only. The information screen shows the change in speed when I rotate the blower knob however the blower motor is always on full speed. The only way I can get the blower motor to stop is to go into the Climate settings in the information screen and turn the system off.
So I disconnected the power from the blower motor and ordered a new BMR31677 resistor.
It seems like you can blow other components on the resistor circuit board that cause the resistor to fail even though the fuse is good.
In the meantime, I will recheck my soldering on the resistor repair to make sure I haven't accidentally soldered two of the connectors.

 

I just pulled the engine and trans from a 2008 XK and decided to take some documentary photos of the measurements in case anyone wants them. Evidently this duck bill had already been cut . I also took a picture of the hole without the duckbill in position.

Measurement from the metal ridge

photo of the hole without the duckbill in place

Already trimmed

 

Are you sure that’s trimmed, and not just the newer version of the duckbill?

 

Engine out ??

Are you rebuilding it

 

Actually not. I had bought the car as a salvage for another project and removed all of the bits that I could off of the carcass before it went to the scrap yard. It always seems like I have two cars of any make laying around. One whole and another in pieces in boxes waiting for some Jag owner(or myself) in need of a part! Fun(sometimes) hobby of mine.

Picked pretty clean with the exception of the seats which were rusted up from the inside due to residual water getting into the cockpit before I got it.

 

Well, I would do this procedure once a month as a precaution, can help preventing all these headaches.

 

Duck bill tool made from 1/4” brake line and an inner motorcycle speedometer cable. The business end of the cable has been ground to a sharp point and can be turned and pushed in and out from the other end.


 

But did it do the job!?