Hello all! Before I ask my question, I would like to say that I've asked a couple things on this forum, that had me stumped, and folks answered me promptly and with GREAT information. I super appreciate it! I hope to be able to return the favor to some peeps when I get more knowledge on Jags. Just wanted to say thanks!

Here's whats up.
Day 1: climb in to the car, fire the heater up. Everything works. Hot air blows in my face, my car is comfortable. Come home, park, go to bed.
Day 2: climb in to the car, fire the heater up. Zip. Nothing happens. No twitch, breeze, or any kind of response. No controls illicit a respond; it's like the system up and left the car.

Doug, I read in a previous post of yours that I should check all my fuses and such, and it's on my list. Outside that, is there a common switch or wire that goes bad that maybe is easy to replace, or maybe has my blower motor gone bad?

Thanks!

 

Help us to help you! I assume it's an XJS from where you posted; give us the model year, engine type etc. and we'll all know what systems we are talking about.

 

Whoops, rookie move.

1982 Jaguar XJS, V12 model (chevy V8 swap)

 

On an '82 you should have 4 climate control fuses. Two in the RH fuse box (as far as I can remember), one behind the console's RH "cheek panel" (in-line fuse on brown and brown/yellow wires) and one on the ground wire for the amplifier behind the LH console cheek panel.

Be mindful that old fuses can look OK but be broken under the cap and look for dirty fuse clips/contacts as well.

Also, a Lucas 50amp fuse = USA 30amp.

To clarify, nothing happens even if you select "defrost" ? It's important to know becuase in "defrost" the auto control is bypassed.

Cheers
DD

 

There is a sensor attached to the inlet pipe of the heater core. It prevents the fans from running until the coolant is warmed up so it won't blow cold air. If it is failing or its connections are corroded it may cause your problem,

Another possibility is that your heater valve is not always opening. If so, that same sensor would not see adequate warm water temperatures.

If the valve is functioning properly you should get warm air flow at speed, even without the fans running.

As Doug mentioned, the defrost function should over ride everything I mentioned here.

Please let us know what you find.

 

Well, I finally took some time to figure out what was what, and my first discovery was that someone had changed out the 50amp fuse that runs the a/c fan (I think) for a 35amp, and that it had gotten so hot that it melted the fuse, the housing, and warped the metal prongs that hold the fuse in place. I'm surprised I didn't light myself on fire the first time I turned the heater. So, I'm replacing the fuses one by one and seeing if that fixes it, but I'm having a hard time finding a glass 50amp fuse, so I'll let you know after I get my hands on one if that was the problem.

 

WARNING Will Robinson - if the fuse and holder have melted with a 35A fuse there is something amiss other than the fuse. You need to find the cause of the problem the fuse holder should not melt even with a NIAL in there unless there is some other problem.

A trick I used when on the bench so you didn't have to replace the fuse 100 times was a light globe in place of the fuse a 60-100W will do. It must be an incandescent globe, you know the old type. What to do use an old fuse and solder wires to each end so it can be placed in the fuse holder, next solder the wires to the terminals on the globe.

If there is excess current draw the globe will light up. This also allows you fault find without damaging the rest of the CCT.

cheers Warren

 

Oh don't forget to tape everything up so it does not short on anything

 

Check the contacts and spring tension in the fuse holder.

Poor connection = high resistance = melted plastic

As mentioned earlier, a USA spec 30 amp fuse = a Brit spec 50 amp fuse. You won't find the Brit/Lucas type unless you go to a Brit car specialist. Not worth the bother, really.

Cheers
DD

 

Doug! Nice, i didn't know there was a conversion. That would explain why I can't find myself a 50amp fuse... American style. And Warren, thanks as well. I'll try out your idea and see if there is something else going on. The metal contact points were very very loose, so it is possible that it was arcing and causing a ton of heat. Which would explain the melting plastic.

Oh yes, and when I switch to defrost, I do hear a whirring noise for a second in the upper dash, but no fan. And I'm still getting warm air into the cabin, which I'm assuming is being pushed in through the heating system just as I'm driving.

 

Swapped out for a 30A and the heater fires right up! Thanks guys, another problem down. I knew going into this that I'd have issues with the electrical systems, but fortunately it's fun to troubleshoot stuff.

Thanks again!

 

Take a Saturday and clean every fuse holder, every fuse end cap, and every relay socket and wiring connector that you can reach....and clean and tighten as many grounds as you can find. With that done you're about 80% along in solving the notorious Jaguar electric problems. Repeat the drill in 10 years :-)

Cheers
DD

 

Lol

:-D

 

Good advice from Doug, I did my AC a couple of months ago and it solved a lot problems until the rain across the Nullabour through the leaky windscreen. Next time I am going to use a good marine electrical contact sealant to keep the moisture out of the mostly the earth tabs

http://www.jamestowndistributors.com...ct.do?pid=2720

cheers Warren