Can cluster removal drain the battery?

[chrisca70]

I recently got a pretty decent E30. First I did was to replace the battery (Autozone duralast 47-90- DL). Yesterday, I removed the cluster to replace the gears and SI batteries. The car slept with no cluster. Next day, I left home without the cluster, drove it 6 miles to work, sit for a few hours, and on the way back home, the car died on me. Just before dying lights stopped working, windows got slow, etc. With the car dead I measured the voltage at the battery points under the hood (8.7V) and at the battery (9.3V); Obviously the battery was quite discharged, someone help me to jump start it and it started right away and I managed to get back home.

Question: leaving the car without the cluster for a day could cause such a battery drain?

[brbahner]

nope

[Todd Black 88]

Yes, driving it without the cluster will not charge the battery.
Cluster battery bulb is needed for alternator to charge on earlier cars, but all cars need the cluster in, because the battery bulb circuit provides exciter wire to the alternator.

This is a late model etm, early model does not have the resistor beside the charge bulb.

[chrisca70]

Thank you so much! once I put the cluster back it I will charge the battery and all should go back to normal.

[brbahner]

Yes, driving it without the cluster will not charge the battery.
Cluster battery bulb is needed for alternator to charge on earlier cars, but all cars need the cluster in, because the battery bulb circuit provides exciter wire to the alternator.

This is a late model etm, early model does not have the resistor beside the charge bulb.

This makes sense, but then why was i able to drive my car without a cluster for a good 2-3 months with no issues whatsoever with an old battery.

[dnguyen1963]

This makes sense, but then why was i able to drive my car without a cluster for a good 2-3 months with no issues whatsoever with an old battery.

Don't see how you could.

[jlevie]

An alternator can self-excite, but one can't be sure that it always will.

[blunttech]

An alternator can self-excite, but one can't be sure that it always will.

This is true for me also