Alternator Charging

Good morning everyone,

I recently put a new battery in my truck. The gauge on the dash was showing low charge. It was reading about 11.5 Amps. While doing my timing job, I decided to change my alternator. After putting the truck back together with a new alternator I noticed my dash was showing zero charge when I started the truck.

As a sign / confirmation that the truck wasn’t charging the truck died out. So I disconnected the battery. Went under the truck and checked my connections and checked to make sure the 10mm bolt holding my ground wire was tight. Everything looks to be snapped it properly and tight. Jumped the truck and got it started again, but shortly after it wouldn’t stay on.

I’m curious if it’s a bad fuse or a bad alternator. I got the alternator from rock auto as a rebuilt Denso. I would like to test the alternator before going down the rabbit hole of exchanging from rock auto. Any tips to test the alternator before I rip it out and decide it’s a bad alternator or can I test anything else to show me why I’m not getting any charge?

 

First thing is to pull the battery and get a full charge on it. Eliminate that part of the system. The truck should then fire. After it does, you can check the voltage coming from the alternator.

 

What ATBAV8 said.

 

If you have an OBD reader, you can check the voltage with the truck off versus with the alternator running. My daughters Civic was hard starting, showed only 10.2 volts not running, but 14 running. Knew at that point it was a battery problem. Over 5 years on the original battery and it finally decided to charge correctly.

 

You need a multimeter so you can measure the voltage with the truck off and with it on. You can get a cheap multimeter for $8 at Harbor Freight that will do the job. But if you go to ACE Hardware or Home Depot, you can get an decent quality inexpensive ($35-$40) Klein brand that will probably last you the rest of your life.

Without knowing the battery voltage at rest and while running, you're just swinging blindfolded.

 

Most of the flaps can test both your battery and alternator.

 

I 2nd the nomination ^^^.