# My Ford Ranger Suddenly won't start **URL:** \ **Category:** Factual Questions\ **Created:** [August 5, 2011, 2:14am UTC](https://boards.straightdope.com/t/my-ford-ranger-suddenly-wont-start/591529 "2011-08-05T02:14:59Z")\ **Posts on this page:** 6\ **Page:** 2
**Author:** ![thelabdude](https://avatars.discourse-cdn.com/v4/letter/t/dc4da7/32.png) [@thelabdude](https://boards.straightdope.com/u/thelabdude)\ **Post date:** [August 7, 2011, 2:14am UTC](https://boards.straightdope.com/t/my-ford-ranger-suddenly-wont-start/591529/21 "2011-08-07T02:14:43Z")
> [@Rick](#): > > The diodes in the alternator filter out the AC ripple, if AC ripple is present in the car, the alternator is bad, not the battery. If you still insist that the battery filters AC out of the system, cite please. > -Rick who has taught this stuff for more years than I care to think about. Any rectified AC current has ripple. That is why electronic power supplies always have coils and capacitors. The 3 phase produces much less ripple than household single phase, but still ripple. I am not digging up a cite for that or one for the sun coming up today. ---
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://boards.straightdope.com/u/Rick)\ **Post date:** [August 7, 2011, 3:21am UTC](https://boards.straightdope.com/t/my-ford-ranger-suddenly-wont-start/591529/22 "2011-08-07T03:21:19Z")
> [@thelabdude](#): > > Any rectified AC current has ripple. That is why electronic power supplies always have coils and capacitors. The 3 phase produces much less ripple than household single phase, but still ripple. I am not digging up a cite for that or one for the sun coming up today. :rolleyes: When used by an automotive professional the term AC ripple has a particular definition. That is AC current of 0.4V AC or greater measured at the battery. In the automotive industry if someone says "That car has an AC ripple it means that there is an alternator problem, they are not referring to the few hundredths of a volt fluctuations in the output voltage alternator. ---
**Author:** ![Dag\_Otto](https://avatars.discourse-cdn.com/v4/letter/d/439d5e/32.png) [@Dag\_Otto](https://boards.straightdope.com/u/Dag_Otto)\ **Post date:** [August 7, 2011, 1:46pm UTC](https://boards.straightdope.com/t/my-ford-ranger-suddenly-wont-start/591529/23 "2011-08-07T13:46:44Z")
> [@bump](#): > > Yeah, on re-reading it, you’re right. Guess that’s what I get when trying to post and help my wife take care of our one-week old infant! > > On that note… I’m dreading when my current battery will crap out. It’ll probably be the coldest day of the year; my current battery’s about 5 years old, and we’re in the middle of the second-longest 100+ temp streak in Dallas history at 36 days, with at least another week or two to go in the streak according to the forecasters. Preventive maintenance is always an option. ---
**Author:** ![Magiver](https://avatars.discourse-cdn.com/v4/letter/m/4491bb/32.png) [@Magiver](https://boards.straightdope.com/u/Magiver)\ **Post date:** [August 7, 2011, 3:58pm UTC](https://boards.straightdope.com/t/my-ford-ranger-suddenly-wont-start/591529/24 "2011-08-07T15:58:24Z")
Rick, I’ve witnessed radio static due to bad batteries on so many cars I can’t even give you a count. It mirrors the same sound picked up on AM radio that an AC brush motor creates. I take advantage of this effect when trying to locate electrical lines underground. I run an electrical drill on the circuit and walk around with an AM radio. The op described the phenomenon which I assume went away after the battery was installed. There is definitely a filtering affect associated with a normal battery. Whether a good battery actually filters an alternator or a bad battery doesn’t have enough power to properly work the capacitors is a technical issue but the diagnostic aspect is still the same. Loss of power and radio noise = bad battery. I personally think the battery smooths out the DC current pulse out of general common sense but my electrical degree consists of one HS class on the subject. ---
**Author:** ![Magiver](https://avatars.discourse-cdn.com/v4/letter/m/4491bb/32.png) [@Magiver](https://boards.straightdope.com/u/Magiver)\ **Post date:** [August 7, 2011, 4:07pm UTC](https://boards.straightdope.com/t/my-ford-ranger-suddenly-wont-start/591529/25 "2011-08-07T16:07:03Z")
> [@Dag\_Otto](#): > > Preventive maintenance is always an option. I personally have not had a modern battery make it to 6 years and I average probably 4 start cycles per day. Extremely anecdotal in the face of the number of cars on the road but I wouldn’t drive on a 5 year old battery if I lived in an area of poor phone coverage and harsh weather. ---
**Author:** ![thelabdude](https://avatars.discourse-cdn.com/v4/letter/t/dc4da7/32.png) [@thelabdude](https://boards.straightdope.com/u/thelabdude)\ **Post date:** [August 7, 2011, 4:48pm UTC](https://boards.straightdope.com/t/my-ford-ranger-suddenly-wont-start/591529/26 "2011-08-07T16:48:06Z")
As a voltage pulse from the alternator rises, the power it take to charge a good battery limits the voltage rise. As the voltage from the alternator drops on the down side of the pulse, power flows out of the battery to hold the voltage up. With a fat wire running between the alternator and a good battery, you will never see the pulses with things working right. Overall, when things are working right, the alternator put out enough power to supply loads and maintain the battery at the proper charge. [Previous page](https://boards.straightdope.com/t/my-ford-ranger-suddenly-wont-start/591529.md?page=1)