I have a 1998 E300TD with 122,000 miles on it. I started having a problem with the horn, garage door opener and sometimes the auto door locks. The horn and garage door opener work when the key is in pos. 2 but when the car is started the horn and garage door opener do not work. The garage door opener is not an issue but the horn is a safety feature and needed to pass inspection. All the fuses check out (engine, drivers side door and under back seat). Is there something in the computer that would tell the horn not to work when the car is started? I disconnected the battery for about 20 minutes and it does the same thing. I know it was disconnected long enough because the BAS code came up which was caused by the voltage drop.

I know there is something probably simple that I have missed but with the vast experience and brain power of this forum I know someone has had this experience before.

Any help would be greatly appreciated. Oh and one other thing is that when the car is first started and is driven in about 200 yards there is a hesitation like a vacuum switch or something then the car drives perfect.

The horn fuse is on the K40 relay module. It's in the module box under the hood. That fuse or the module may be at fault.

I ordered a K40 relay today $96.68 delivered from Ken Garff in S.L.C. I hope that solves the problem. One other thing I noticed is that the auto door lock is locking the doors now. I believe they are suppose to engage when you hit 10km/hr or 6 mi/hr. Is there a diagram of the functions that the K40 performs? The way it's talked about in the forum is that it's almost mystical. No doubt it is mystical to me but with a diagram...........

Thank you in advance for any help.

I have not replaced the K40 relay yet. I still have four things that won't work when started (horn won't work, garage door opener won't work, sunroof won't work and the auto door locks won't work). After doing a search on sunroofs I tried the resync (pushing up on the tilt for a few seconds with the key in the 1 position) the sunroof started to work and then every thing worked after I started the car. I took a short drive (around the block) and the auto door locks worked as well. When I came back turned the car off and started again I had the same problems with the (horn, garage door opener, sunroof and auto door locks.)

Is there something in the key switch that would make these not work when I start the car? Why would they work a couple of times after resyncing the sunroof? I can only imagine how much a key switch would be if the key alone is about $200! Since this is my wifes car I am under the gun if you know what I mean. Other than this problem the car is an absolute dream to drive (I did an upsolute chip with high performance tires). I don't see how the chip programming would cause these problems since its been on the car for about 3 years with no problems.


Regards,

Logan

I did a search on ignition switches and found that a guy had the same thing happening with his horn and it wouldn't let him pass inspection. He turned the key different and it worked.
I didn't even think about the key positioning. My horn, sunroof, garage door opener and auto door locks stopped working when you start the car. I read this post and put the panic button at 6'oclock and everything worked. I also tried the spare key and it did the same thing (panic button at 12'oclock horn etc. not working but panic at 6 things worked fine. With the key chain hanging it's not the natural feel to put the key in with the panic @ 12'oclock. Does this have anything to do with the ignition switch going bad?

I've got a K40 relay on the way just in case. I didn't read the owners manual cover to cover in order to a book report on it. I have a feeling that this car will be with us for a long time. I like to service the car my self to let the car get the rescpect she deserves. This car has to perform at it best at all times. The cargo is priceless (my stunning wife, amazing daughter aspen and finally kindess soul and keep of my heart. Kaitlyn). Thanks again.

Now that you mention it, the ignition switch does sound like a likely culprit.

Note that if you don't need the K40 now and it is the original part, you will need it soon enough.

I'd say that if it solves the problem 100% of the time that it must be the iginition switch itself which is bad. It is odd that it would allow you to start the car but not "turn on" the accessories...but you can't argue with succesfully debugging it the way you did to find a workaround. I'm not sure if you can replace the switch yourself or not...anyone know if this has to be "coded" to the car like so many other parts of the key system?

__________________
Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz