Dimmer fuse keeps blowing

Hello Everyone,

This problem started today. All I did was wash and wax the car and drive with the AC on. The left seat/mirror/dimmer fuse keeps blowing. This happens whenever I turn on the running lamps. The dash lights up for a split second and then the fuse blows. If I change the fuse and leave the ignition turned off, there’s no problem. If I turn the key to on with the running lights or headlight on, the fuse blows again. What could be causing this? The running light and headlights still work. I just have no dashboard lights. Again if I change the fuse and turn on the dashboard lights, everything is fine as long as I leave the key off.

Darren,

What year and model are we talking about - and which fuse blows???

It’s a 1993 XJ6 and the fuse is in the front left panel. It’s for the left power seat module, left mirror and dimmer. It’s a 10 amp. I believe it’s the A1 fuse. The power seats and mirror are fine.

Darren,

Very odd!

Let me see if I have this straight.

  1. If you switch on the ignition (but none of the lights) the dash illuminates as normal and the seat adjustment and door mirror adjustment on both sides work fine?

  2. If you do not turn on the ignition but turn on the sidelights (is that what you mean by ‘running lights’?) or headlights every thing is fine?

  3. However, if, with the lights on you then turn on the ignition, fuse A1 in the left side fuse box blows and (obviously) the seats and mirror adjustments no longer work?

  4. Similarly, if, with the ignition on and the seats and mirror adjustment working OK you then turn on the lights, fuse A1 also blows, extinguishing the dash lights and killing the seat and mirror adjustment?

It is difficult to see any direct relationship between the seat/mirror function and the side or headlight function but the only clue I can come up with is that separately they both use an element of relay module ‘H’ (yellow base under dash).

‘H3’ acts as the ‘Auxiliary Sidelight Relay’ which is energised when you throw the sidelight switch.

‘H1’ acts as the Auxiliary Power Relay’ which is energised when you turn on the ignition with illuminates the dash lights and of course powers up the seat and mirror ECU.

Since Relay Module ‘H’ is buried below the glove box under the dash, it is difficult to see how that could be affected by simply washing and waxing the car - but it is a Jag, so I guess anything is possible! :slight_smile:

Anyway, have a look at that relay module just in case. Beyond that, I’m out of ideas!

Hi Bryan,

Today no symptoms. This car can indeed be a problem child. Yesterday, the A1 fuse would blow any time the headlight switch was moved to a position other than off when the ignition was turned to run. The problem wouldn’t occur if the ignition was in the off position. I did notice that turning on the ignition brings the climate control pane lights into the mix. I don’t know if this has anything to do with it. I removed the headlamp module today and it looks like brand new-no signs of trauma whatsoever. I couldn’t get the dimmer module out-it wouldn’t budge. It is mounted on the left side of the steering column. Today, however, it acted like the problem never happened. I don’t know if I waterlogged the mirrors when washing the car and caused them to create some type of short circuit that draws more current than usual and the blew the fuse when I turned on the dash lights. One never knows with these cars! I can’t duplicate the problem today.