Electrical problem driving me crazy

This problem is intermittent and very hard to diagnose. For reasons unknown to me, the A1 fuse in the left hand fuse panel will blow if I turn on the side lights or headlights, but only if the key is on. I then lose the dashboard, heater panel, clock panel and window switch lighting in addition to the driver’s side power seat. The fuse is described as driver’s seat ECU, heated mirrors, dimmer. I do realize that with the key off, only the dashboard lights come on with the headlights but with the key on, all of the other locate lights come on also. If I unplug the connector from the back of the heater panel and plug it back in, the problem seems to correct itself until the next time. This seems to be happening more often than before. I removed the heater panel and tested the backlighting circuit with an ohmmeter. The heater panel has 5 bulbs and therefore uses quite a bit in the circuit. I don’t think the heater panel is the problem though. I think something else is causing an excessive current draw when the headlight switch is operated with the key on and blowing the fuse. The headlights and sidelights continue to work through all of this. All the window switches light up when the fuse is not blowing, as do all of the other locate lights. I’ve checked the relays under the glove box and they seem fine. The heated mirrors work as they should. Could the headlight switch/dimmer module be failing?

Sounds more like a short when the switch is operated for it to blow the fuse. Process of elimination I’m afraid. Easy way is to disconnect everything off that fuse and reconnect one by one until it goes again.

It could be the switch also.

Darren,

I can’t see any obvious relationship between switching on the lights and the effect that would have on the circuits served by that fuse A1 - although there obviously is one or the fuse would not blow.

If I were faced with that problem I think I would remove fuse A1 and insert the probes of an ammeter in the fuse holder to measure the actual current draw as you switched the ignition on and the increase as you then switched the headlights on. But be prepared to remove the probes quickly before something starts to over-heat!

To blow fuse A1 you must be getting more than 10 Amps and I can only think that a problem with the mirror heaters or similar served by relay module G would cause that.

Hello folks,

I guess I will have to start the process of elimination. I like the ammeter idea, at least if I see smoke, I’ll know which component is failing :slight_smile:
The heated mirrors get nice and toasty when the defrost switch is on, so I don’t think it’s that. Right now-for now, the fuse is not blowing.