How to Test an Alternator

Diagnosing Alternator Problems. Learn how to test an alternator with a Multimeter. Does your car not start, do you have dim headlights or interior lights, does the starter sound weak when start the engine, or does your car die sitting overnight? This video will show you a few ways to test your alternator to see if it is bad, is going bad or is good. A good alternator will show a charge at around 14.2-14.7v while the car is running and under an electrical load it wont drop below 13v.

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Disclaimer:
Due to factors beyond the control of ChrisFix, I cannot guarantee against improper use or unauthorized modifications of this information. ChrisFix assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. Use this information at your own risk. ChrisFix recommends safe practices when working on vehicles and or with tools seen or implied in this video. Due to factors beyond the control of ChrisFix, no information contained in this video shall create any expressed or implied warranty or guarantee of any particular result. Any injury, damage, or loss that may result from improper use of these tools, equipment, or from the information contained in this video is the sole responsibility of the user and not ChrisFix.

[jumpercable]

Hey Chris, I'm a retired auto mechanic, with 4 years experience at General Motors Assy Division, (Back from 1978--1981), then 15 years as ASE cert master at a Chevrolet Dealer, then 4 years at an automotive mechanical claims facility (Call center for under 800.00 repairs). I have to thank and congratulate you for the outstanding job you're doing. You are helping people and asking nothing in return but for people to subscribe to your channel. You are helping thousands of people from being fleeced by the people that take advantage of people that don't know anything about the automobile or the industry that's giving them a bad name due to greed and corruption. My guess is the thumbs down people are the ones losing money thanks to your YouTube help. I just want to thank you and salute your help to people that are tired of being screwed by the shops and mechanics that are more concerned with making money than keeping customers happy.

[TDMack]

Finally, someone that do an instructional video that's to the point and no rambling about irrelevant matters unrelated to what the viewers are seeking. Chris you are the textbook example of how videos for DIY's should be done. Thank you much.

[reneecollins]

You are my hero. Since I lost my husband I've had to figure out how to do a lot of things on my own. The information you provide is detailed and specific and clear and anytime I watch one of your videos I come away with confidence that I have learned what I need to know from you. I appreciate so much everything you post because even if it doesn't apply to me today at some point I'm sure I'll need the information and the information you provide is so good thank you so very much for everything you do.

[columbia]

I really enjoy your tips and this one saved me a ton! Our 6 year old Lexus had trouble starting so I took it to Lexus. They said I needed a new battery ($400) and a new alternator ($600). They charged me $120 to diagnose! I guess I should have just gone to an auto store! Looking at the battery I noticed it was the original and there was a label indicating an 84 month warranty. I asked the service advisor and then he told me that I was eligible for a 25% proration off a new battery so it would be “only” $300 but he highly recommend terminal cleaning and protection for an additional $25. I was pissed so I paid the $120 diagnostic fee and drove it home.

I went to Costco and bought a larger AGM battery (27F vs 24F) and it fits perfect. I then followed your steps and discovered that the alternator is fine.

I could kick myself for taking it to the dealer for diagnostics but I didn’t know how to check the alternator until later.

Thanks and keep up the great work!

[ricardosegoviajr]

Outstanding video. Shady mechanic told me I had a bad alternator. Ran these test and it was within the mentioned volt range. All that was needed was to clean connector to alternator. You saved me $350. THANK YOU!!!!

[bibo]

Man, Life would have been easier 50 years ago if we had the internet. Life is getting better in a lot of ways. Not all though. Thanks, and you deserve your subscription and view numbers.

[davehawkins]

Chris, you are a ROCKSTAR! Thank you for helping me fix pretty much every issue I have had with my vehicles. You’ve helped me save $1000’s of dollars doing it myself! Thanks man!

[bigbenchrob]

Your video came up in a Google search for “how to test alternator”. You concisely provided exactly the information I needed to answer my question. Without all the crap. Sincerely, thank you!

[CatalystSM]

One of the best auto DIY videos I’ve watched. Easy to follow, explained well without over doing it. Extremely helpful- thanks.

[johnbox]

Just saved me $150! Cleaned connection to alternator and now it is working like new!

[MikeBrown-iipt]

It's been a while since I've had to test an alternator so I needed a "refresher course". I'm glad to have found this simple, too the point video that told me everything I needed to know. It helped me figure out that my brothers car didn't need an alternator but just a new battery. We had several days of sub-zero temps last week and his battery gave up. Now, if I can only get him to reimburse me for the price of the new battery lol!

[Scyther]

Can’t thank you enough. You helped me determine that my alternator was, in fact, bad but more importantly when it came time for me to replace it I paid extra close attention to the wires and bolts only to find that my negative terminal on the battery was rusty, the chassis ground was loose, AND the chassis ground wire was frayed. As soon as I replaced the alternator and negative terminal wiring my car started right up and it sounds better than ever. Thank you so much.

[JamieDelour]

Chris, you're doing a great service for people far and wide! Thank you

[debruin]

This video was awesome! Did the negative voltage drop test on the alternator. Found I had 0.8Vs of drop between the alternator housing and the battery! Pulled alternator and cleaned/sanded brackets and bolts and boom! Alternator putting out 14.4V instead of 13.8.. under load it was below 12.75V before cleaning. After cleaning it held over 14V with everything turned on. Great tips! Thanks Chris!

[lamusicamees]

1989 Jeep YJ owner here. Thanks Chris for this very well explained video and giving me clear instructions on how to check all this and the reasons and logic in strange readings. Brilliant video. Thanks for reaching me how to figure these gremlins out and what to clean and replace. 100/100

[tempgar]

Thanks for an elegant, good, informative, clear, uncluttered video. I didn't have to sift through bad comedy or bad music or other gimmicks but just got what I needed. Well done and thanks again.

[WilliamDye-willdye]

Yesterday I replaced the alternator on my 1G DSM (a 1991 Mitsubishi Eclipse). This was a very big deal for me, because I don't know much about cars. Replacing an alternator was the most complicated auto repair task that I'd ever attempted, so I watched several YouTube videos to help me understand what I was getting into. This video was one of the best, so thank you for posting it. The new alternator seems to be working great so far. I plan to check on it during the next few days, using sources such as this video as my guide. Thanks again.

[lando]

I was always told to disconnect the positive cable from the battery and if the car shut off, it was the alternator. I just checked everything like you described, and it turns out that it is the alternator not producing enough current. I'm still going to use your tips, especially after I install the new one. Thanks for your tips on properly diagnosing an alternator, I'm sure you've saved a lot of people a small fortune.

[anitamackeigan]

Finally, someone who speak plain simple language and doesn't ramble on or try to sell something!! Thank you!!

[fongdeep]

Love your videos Chrisfix! I used this video to diagnose an alternator issue with my 2008 Civic. It's almost at kms and your detailed and thorough videos are a big part of helping it make it to that milestone!