Electrical Issues

[johannmaximus]

I'm having a few issues with my '89 325iX. The biggest issue, and the biggest headscratcher involves the blower fan. Every time I turn it on, the fan works perfectly, but the fuse itself will burn up. It won't blow, just smoke and burn up. I think a PO had the same problem, because the fuse box is modified with thicker wiring and a 30 amp fuse at fuse 20.

Problem two is the tachometer, fuel economy gauge, and the OBC. All of a sudden, all of them just stopped working. The fuse is fine, but I do think there is a short somewhere. If anybody has had this problem, and knows how to solve it, I would be very appreciative.

[Gregs///M]

I'm having a few issues with my '89 325iX. The biggest issue, and the biggest headscratcher involves the blower fan. Every time I turn it on, the fan works perfectly, but the fuse itself will burn up. It won't blow, just smoke and burn up. I think a PO had the same problem, because the fuse box is modified with thicker wiring and a 30 amp fuse at fuse 20.

Problem two is the tachometer, fuel economy gauge, and the OBC. All of a sudden, all of them just stopped working. The fuse is fine, but I do think there is a short somewhere. If anybody has had this problem, and knows how to solve it, I would be very appreciative.

First problem,

You heater blower motor is probably shot and pulling more current than it should. Since your PO installed new wiring of thicker gauge, it is a sure sign of a band aid fix. I would say your car is at risk of fire until it is replaced or fused removed and you do not power it anymore. I suggest you buy a new one or good used one and swap it in. If your problems continue, you can suspect a short in the wiring. HOwever, a short in the wiring usually blows the fuse right away.

Problem two,

These are all classic signs of a failed SI board. Once the batteries on the board die, all of these gauges fail to operator intermittently. You can replace the batteries yourself or purchase a refurbished SI board from me. You can check my "services" section in my signature for more info on this.

[johannmaximus]

First problem,

You heater blower motor is probably shot and pulling more current than it should. Since your PO installed new wiring of thicker gauge, it is a sure sign of a band aid fix. I would say your car is at risk of fire until it is replaced or fused removed and you do not power it anymore. I suggest you buy a new one or good used one and swap it in. If your problems continue, you can suspect a short in the wiring. HOwever, a short in the wiring usually blows the fuse right away.

Problem two,

These are all classic signs of a failed SI board. Once the batteries on the board die, all of these gauges fail to operator intermittently. You can replace the batteries yourself or purchase a refurbished SI board from me. You can check my "services" section in my signature for more info on this.

Problem 1: That's what I was worried about. Other sources say that the blower motor wouldn't work on all its settings if it was drawing too much current. I don't know though, so I'll plug in a new fan, and try to put in a new fusebox.

Problem 2: I looked into it more, and it turned out the fuse had blown. If the SI board fails, does the speedo fail as well?

[Gregs///M]

#1, this is not true. The fan can pull its over current at max setting. It can definitely still operate at full speed, yet pull more current than rated. I recommend you disconnect the blower, at the connector local to it. Then test all your circuits with new fuses. If no fuses blow, the blower itself needs replacing.

#2. When the SI board batteries die, the speedo will continue to operate.

[StereoInstaller1]

Greg is 100% spot on.

Pull the fan cover and spin the thing, that should tell you quickly about the fan

[johannmaximus]

Greg is 100% spot on.

Pull the fan cover and spin the thing, that should tell you quickly about the fan

What is the fan supposed to do when you spin it?

[AndrewBird]

It should spin freely and for several seconds. Basically the bearings in them wear out, get sticky/rough and therefore the motor has to try harder to turn, drawing more current.