Every year about this time I get my 95 XJS, 4.0L out. I keep it in my garage with a battery tender on all winter here in upstate NY. Every year I have the same problem, my horn stops working over the winter. Once I start driving it, it eventually starts to work and will stay working for the rest of the driving season. Unfortunately it also needs to be inspected in April and quite often it’s not working when I take it in. I’ve checked all the obvious things; fuses, relays ,etc. It’s always both horns and when they start to work they both come on the same time. Any ideas? Thanks!
Does it start working by itself, or after you’ve tried honking it a few times?
I would suspect contacts in steering wheel. If so, either take it apart and clean, or honk the horn 100 times to clean them?
I keep trying it as I drive and eventually it starts working. Then it is usually OK for the rest of the season unless it sets for a couple of weeks.
yeah, that sounds like corroded contacts to me. My steering wheel, before airbags, is super easy to remove and check. Not sure how you check yours since it has an airbag in it.
My 88 XJS had been sitting for years, I tried the interior fan switch for the heater, and nothing. Thought it was dead. Tried the switch back and forth a few more times, and now it works fine.
When I opened up the dash to work on the instrument cluster, I saw a few contacts in there badly corroded. Even the copper was corroded.
All I’m saying is, our Jaguars seem to like to corrode from non-use.
It astounds me that any horn would still have contacts. Horns are rarely used, but when you need it to work, it needs to work! Having to pound on it for a while before it starts working again is unacceptable.
Most cars have two horns, and they are two different pitches. The pitch is varied by adding more weight to the diaphragm of one vs. the other. So they resonate, and the resonant frequency of the heavier diaphragm is lower. As they resonate, they bounce on and off the contact, driving the coil that drives the diaphragm.
In any sane car company, that set of points would have been replaced in the 1970’s by a transistorized circuit. Turn on the power and then dial a little pot to tune the circuit’s frequency to match the diaphragm, which means where the thing is the loudest. Install and forget, the horn will never fail to work when called upon again.
It’d probably be a good idea to make that upgrade as a retrofit. You’d have to modify the horn to bypass those stupid points. And some EE needs to gin up a schematic for the transistorized circuit.
I think they are talking of the horn contacts in the steering wheel area.
They both go bad at the same time? I’m having the same issues with my 96.
Several years ago, I came across a new old stock steering wheel for my car. I installed that, and one of the horn buttons wouldn’t work, so I replaced that too. So I have a (relatively) new wheel, new horn button and old horn button… They all went bad at the same time?
I’ll pop them off this weekend, clean them up and see if I can spot any evidence, however I just keep shaking my head at this thought.
Thanks everyone for the prompt replies. Both of my horn buttons work the same, when it works, they both work, and when they don’t, neither of them will. Same with the horns. I don’t have to push hard, it just starts working, which makes me wonder if it’s the buttons. I’m don’t want to mess with the steering wheel with air bags. When I first test drove the car 5 years ago, I mentioned to the owner that the horns were not working. He seemed surprised, and went over to check them and of course they worked. Every year I try to figure it out.
In the XJ the relay might be stuck, or the interface between wheel and stationary wiring corrodes. In the former case if there is one, substitute the relay which you probably have and maybe check for voltage. For the slipring (or whatever) area moving the wheel often and maybe adjusting the position a few times could help. That is, in case it is wired instead of a moving connection you are moving the wires around a bit when you adjust the wheel. Also check and clean all the grounds.
The easiest start is to get the multimeter out the next time it happens and measure for voltages to ground at the relay, and resistances between horn ground relay ground and body so you have an idea about the location of the problem?
A good squirt of WD40 into the horns when you lay the car up for the winter will help against them corroding.
It sounds like a wiper is corroding, but I’m not familiar with the XJ-S.