I would have the alternator tested
Battery or electrical.
- Thread starter Dan2002
- Start date
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shreksbrother
Full Access Member
Have you had the alternator tested as several others have suggested? May have saved you the cost of a new battery...
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Matahoe
Full Access Member
Why are you asking this again? I told you how to test it without the alternator...to rule it out.
Martinjmpr
Full Access Member
Nobody here can tell you whether your alternator is bad.
You know who can? Your local auto parts store. Drive there, pull the alternator (it’s a 5 minute job tops) and take it in to have it tested. Even better , if it is the alternator they will almost certainly have one in stock.
Get it done ASAP before you kill that new battery.
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Matahoe
Full Access Member
Rediculous. Sure you can test the alternator at home. If you rule out the wiring and battery. You can test ac ripple and voltage at different rpm's. You can also see amps if you have a clamp meter. There is nothing you cant do at home that a multimeter cant handle. However a pico scope would be ideal.
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SmokChsr
TYF Newbie
My experience makes me think it's going to a bad connection. I recently had a similar but different problem that I found the cure for by accident. In my case I was getting voltage surges that would reset the dash, and cause all sorts of warnings. (not to mention blow light bulbs). What I think to have found that was causing that was a bad connection in the battery current sensor (not sure what it's actually called but it hangs on the negative lead of the battery).
Once I pulled open that connection and put some DeOxit D100 on each contact and exercised the connection a bit it all stopped. From your symptoms you may be looking at something very similar. So I would try cleaning up those connections and see if you see any change. After that it may be the ECM or connections thereof.
The ECM is the device that controls your alternator and charging voltages, and I'm not sure what all information it's using from the current sensor, but from what I've seen if it's not talking to it correctly it's going to do some bad things.
It also could be a short in the Alternator causing those symptoms, but I don't think it is in this case. The main problem will be that if it is the ECM signals most alternator testers won't differentiate an loss of control from the ECM form a bad alternator.
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Thank you for the help. I recently had time and took out the alternator. Went to Auto part store and got it test it and failed the test. Purchased a brand new one , installed it and no more voltage drop .! Thanks again guys.
SmokChsr
TYF Newbie
Well that was a good resolution, and an easy fix. Not many vehicles have an alternator that's as easy to remove and replace as the Tahoe. Also by removing the alternator and testing separately from the vehicle you removed the ECM from the equation.
