Driving without an instrument cluster.

[mikeb23ft]

Obviously this is not ideal, but I don't have a working instrument cluster for my car and I need to make 3 trips tomorrow. About ten miles each. Is there any reason the car won't work without an instrument cluster? I just drove it around the block with no problems but I've heard that an SI board needs to be plugged in for the alternator to charge the battery. Thoughts?

[Gregs///M]

I've heard mixed opinions on this topic. I've done this before, drive with no cluster, and my car died within 15 minutes, maybe 20.

I have a "bypass" but note that I've never actually tried it myself.

In the blue connector, jumper the solid green and solid blue wires together. This powers up the alternators excitation wire and should enable the alternator to charge.

[Andy348]

I drove around quite a bit without one, killed my battery a couple of times. Also didn't realize my car was overheating and blew the HG.

If the car is completely reliable I see no problems driving it short distances (minus the safety issue of not having a speedometer)

[mikeb23ft]

In the blue connector, jumper the solid green and solid blue wires together. This powers up the alternators excitation wire and should enable the alternator to charge.

This is spectacular, thank you. The blue connector that plugs into the back of the speedometer, correct?

As an amendment, I do have a gauge cluster and SI board. When plugged in, the lights on the SI board do come on. None of the gauges are working at all, though. Is this enough to get the alternator to charge, or does the gauge cluster have to be working?

[mikeb23ft]

Also (this is important) does anyone have a pinout for the plug? I need to know which terminals to bridge together. I've checked the ETM and done some Google searches with no luck.

[jlevie]

The answer to your question is in the ETM in the section that shows the wiring to the cluster. But even without looking there, tying system voltage to the exciter input to the alternator will allow the alternator to charge.

[mikeb23ft]

The answer to your question is in the ETM in the section that shows the wiring to the cluster. But even without looking there, tying system voltage to the exciter input to the alternator will allow the alternator to charge.

Unfortunately I'm not very good at reading electrical diagrams. Actually, to be more specific, I can't read electrical diagrams at all. I've stared at it to no avail.

If there are easier routes to tying system voltage to the exciter input to the alternator, I'm all ears. I've got some wire and I'll try anything. I'd definitely prefer not to cut the harness leading to the blue pin that goes to the cluster to tie the wires together.

I really appreciate all the help everyone is giving me, though. If I could drive this car tomorrow it would let me get to my three guitar lessons and make some money that I really need to make. :-)

[jlevie]

Run a wire from the coil positive to the small lug on the alternator. That will supply switched power to the exciter circuit. It would be smart to include a low power fuse (~1A) in that connection.

[mikeb23ft]

Run a wire from the coil positive to the small lug on the alternator. That will supply switched power to the exciter circuit. It would be smart to include a low power fuse (~1A) in that connection.

Good deal. I suppose it would have been helpful if I had mentioned this in my first post, but the car is a 1991 318is and therefore doesn't have a coil, as I am sure you know. What would be a good spot to run from in this situation?

Could I not just go from the big alternator bolt (output) to the exciter circuit? Given me lack of electrical knowledge I almost hate to do any independent thinking in this situation

[nando]

it does have a coil, and it still has a coil power wire. it just doesn't look the same. :)

you could also just jump a resistor between a power wire and the exciter wire right on the cluster connector.

[george graves]

Nando is right. A resistor is a smart idea....or just use a interior light bulb.

[jrobie79]

my 318is I drove for about a week+ without a cluster. Battery never died, gas light still lit up to tell me I was low, worked out fine.

[Cephas]

How did the gas light work if you had no cluster? I'm guessing you had no tach or speedo, but the cluster was still installed.

[jrobie79]

the gas light is a bulb that 'plugs' into the cluster, it's not on of the built in bulbs, i took it out and let it dangle

[Gregs///M]

Even easier idea...Diagnostic connector under hood.


jumper alternator charge socket with battery 12&14