Just had the positive battery cable to the starter replaced, what a difference it made in starting the truck, everything seeming to work just fine, except the battery idiot light flashes on and off at rpms above 1000 during acceleration, the guy that did the work didn’t offer any explanation other than everything checked out ok after they did the work. Any ideas before I go back to this guy to have this resolved. Greatly appreciated thanks.

 

I was under the impression that the light indicates charging circuit is out of spec, ie too low or too high?

 

It indicates that the battery voltage is higher than the alternator voltage.

 

If the alternator charges at about 14.3....Wouldn't the batteries being higher than that be an issue? I know mine usually are at 13.2 - 13.5 when I go to start in the mornings. Then I get 14.3 when running regardless of RPM. Only drops at night when running lights n stuff. Voltage regulator?

 

About a year ago I got a "quick start" alternator installed with proper upgraded wiring and fuses. Things have been going along smoothly until I recently started to see my idiot light flashing as well.

When I stick in my voltmeter into the cigarette slot is shows power from 13 to 14.3 volts. So I tend to agree with Squirrel that it shows a voltage out of spec as well.

Should I be concerned about this? Ideas?

 

I was not going to post anything until @beeper212 chimed in, but now I feel obligated.

2 years ago I had the OEM alternator, OEM starter and OEM class batteries. In October of 2017 (I think) I upgraded the main harness wiring, installed a QuickStart 160 amp alternator, North Star group 65 AGM batteries and a Denso gear reduction starter.

After a few months, starting the truck after it had been sitting for a while the battery light would stay on for a short period. The light will stay on longer when the ambient temperature is colder, like in the 40's than it will in the 70's.

In warmer weather the battery light will go out with a flick of the throttle and during cold weather the light will go out when the engine starts to warm up and after a flick of the throttle.

I have a GP relay light and the battery light is not on in relation to the GP's.

I have a voltage meter in the truck and the battery light is not on in relation to low voltage from the AGM batteries.

I have used a multimeter to test the batteries individually before and after starting with the battery light on. I have used a multimeter to test the alternator immediately after the truck had been started both during and after the GP cycle.

Everything checks out fine. I was reassured by the duplicate readings I was seeing from the on board voltage meter and the multimeter.

I pretty much settled on what @dmd indicated that the alternator voltage is higher than what the PCM is looking for due to the high quality and output alternator. Just yesterday after my truck had sat dormant for a month the batteries read 12.3V just before turning the key to start.

The truck fired up in less than 2 seconds, the battery light stayed on, after 10 seconds I flicked the throttle and the battery light went off. Again, I am confident my charging system is working as I want it, but possibly better than the PCM would like.

Not a big deal for me. Although, I have NOT seen the battery light flash before on my 2000 F-250. So, I could be in the wrong conversation altogether.

 

We need to see voltage from a reliable dvm before starting and while running a few minutes later. Just the pass side battery is fine. If your alt is over or under, that's the issue. I would still pull every ground on the battery cables and do a surgical cleanup and smather them with terminal spray afterward.

Eliminate common maintenance first. You'll be happy with the results, now and down the road.

I wouldn't be looking at the shop that simply replaced the cable. Going nowhere there unless it's wrapped around an exhaust manifold.

A simple check to make sure the repair was effective and not compromised would be probe to the starter connection and to ground and see if there's continuity. I would doubt that scenario because you state that it spins up strong.

Denny

 

I want to thank all guys for your input, gives me a lot more info than I had before.

 

I'd take your truck to an auto parts store and have them test the alternator

 

good idea, thanks

 

I would think forscan would be able to log what is going on as well if the alt test doesnt help any.

 

Excuse my ignorance what is Forscan a type of meter? appreciate all the help I've received. Thanks Walt

 

Forscan is a software program used to monitor the sensors and PCM of the truck. You can achieve the same readings that Forscan would give you with a simple voltmeter or multi-meter. If you were familiar with Forscan and hod a scan tool to hook up to the PCM, I would say sure, go ahead.

For testing voltage from the batteries before starting, testing voltage from the alternator immediately after starting and then again after warm, a multi-meter will get that job done quick and easy.

 

Super I have voltmeter and have used it successfully after trial and error, Thanks

And thanks for your service