The other day I was testing my roadmaster active suspension springs and how they handle the wheel hop. I did about a 50 foot holeshot and no wheel hop which was what I was wanting after forking out the money for them, but my battery light came on. I took the battery and alternator to the local zone and both were good to go according to the tests. I hook everything back up and for the rest of the day good to go, gauge says 13.8 to 14.1 volts at the ecu. Today I go into work and I am watching the gauge for my ecu volts steadily drop until about 11.7 or so volts and my battery light turns on again.

I bought a multimeter tonight and am wondering if I have the alt. to battery cable disconnected at the battery post can I test the disconnected end to check the volts coming from the alt. while the engine is running? can I also test from the post on the alt. as well? Any other tests with the multimeter I can run to make sure its the alt and not anything else?

Thanks

 

You can disconnect the alt cable while engine is running. But your vehicle running base load is around 15 - 20 amps so don't do it for a long period of time otherwise you will drain your battery and stall out the vehicle.

I would just check the disconnected end near the battery. If it is not reading right you might have a bad fuse link in the wire. Therefore, check right at the alt B+ stud. It should be a little higher voltage at the stud vs. at the battery B+, maybe 0.5v.

Check your battery connections and engine grounds. Check the battery voltage with the engine off. It will read > 13v initially after being charged from the alternator. Turn on your head lights and wait a few minutes. The battery voltage should drop down to around 12.7 - 12.8v. If it doesn't read that voltage then either you have a discharged battery or a bad battery that will not accept a charge.

A discharged battery could be because of a bad alternator or simply driving style. However, since you mention that you have low voltage while driving, it likely points to your alternator or something in the wiring.

 

Thanks for the tips. I tested the suspect faulty alternator the other night at the alternator stud and got a reading of .03 volts. Today I swapped out the alternator and all appears good to go for now. However when I put the belt back on and started it the first time the belt got ate up. I had to bypass the supercharger for now with the stock belt and order up a couple from magnuson since I cannot locate one anywhere other than magnuson.