14. Bulb Failure Modules on the 1988-1994 XJ6 or xj40 Jaguar

1: Make sure that every bulb works! The failure module is designed to alert you that a bulb is out, so check this first (easy stuff first).

2: Clean the bulb contacts in the sockets. This is a pain, but this too is a trouble spot. CRC spray electronics cleaner is a good tool to use and it's available everywhere.  Use it outside, please, we don't want anyone poisoning themselves.

3: Brass-based bulbs tend to corrode more easily, so don't use them. The safest bet is to get all of your bulbs from Jaguar.

4: Hooking trailer lights to the lighting harness can also cause the failure module to trigger.

5: Open up the modules and look for broken solder contacts. This is usually the problem with the failure module and can usually be rectified easily with careful application of a soldering gun.

6: Once all of these steps have been taken and the failure module still acts up, you are usually stuck with replacing the failure module.