12.4 charge driving. Replace alternator?

Dennis H · Jan 22, 2019

If not for efi readout, would not be aware. No other symptoms. Should be 13 or 14 right? The dime store power master is about 15 years old. What output and brand is recommended? Battery is ancient too. Is it struggling to charge a bad battery?

dukeboy_318 · Jan 22, 2019

Dennis H said:
View attachment 708709 If not for efi readout, would not be aware. No other symptoms. Should be 13 or 14 right? The dime store power master is about 15 years old. What output and brand is recommended? Battery is ancient too. Is it struggling to charge a bad battery?

Have each tested. Only way to really know for sure. Batteries these days are lucky to last 3-4 years

tonysrt · Jan 22, 2019

Battery life is a crap shoot. My original 05 Ram battery just quit after 14 years and 3 months. My SRT 2010 battery just quit after 81/2 years. When ever I start them I always run them enough to make sure Batt. is fully charged. The SRT I always hooked up a battery tender when not in use, so surprised it quit after 8 years. Although with the higher compression of the 6.1 vs the 5.7 was probably another factor.

Dennis H · Jan 22, 2019

Thanks. Orginal battery in 09 Challenger lights right up and lays a lot. I don’t give up easy.

Dajkzo · Jan 22, 2019

Hi,

I agree, today's generic batteries tend to work and then fail with very little warning. But even with a weak battery you should see 13-14 vdc when the engine is running. Definitely test the system before you replace anything.

Derwud · Jan 22, 2019

This is where having an Ammeter is helpful, but not necessary.. Voltage and Amps, in a good working system slide in opposite directions when working correctly. High Amperage, lower voltage. Lower Amperage, higher Voltage. But, it should not read less then 12.6

Billccm · Jan 22, 2019

Take a meter and go across the battery terminals and measure. Your readout circuit location is unknown.

Derwud · Jan 22, 2019

Billccm said:
Take a meter and go across the battery terminals and measure. Your readout circuit location is unknown.

If he has that large of a Voltage drop from where the EFI is connected (Ate the Battery if they follow the directions) to the battery, he would have bigger problems.
I always start with cleaning the terminals and making sure everything is tight and clean.

69a100 · Jan 22, 2019

dukeboy_318 said:
Have each tested. Only way to really know for sure. Batteries these days are lucky to last 3-4 years

The last 3 batteries I've owned have lasted over 8 years each, of which I'm extremely happy about! The average lifespan of a battery is 4 years, anything after that and your living on borrowed battery. I live by this rule!

toolmanmike · Jan 22, 2019

You could throw parts at it all day and maybe fix the problem. You need to do a complete battery/charging system test to start with.

Dennis H · Jan 22, 2019

I’ll check connections first. There is a large plug receiver new to the battery area since efi. Also put a high power Receiver in recently. I trickle it on occasion. On the subject of variations, the coolant read 151 on the aftermarket gauge and 171 on the Edelbrock tablet at the same time. Different take off points? Suffering from TMI these days.

Darter6 · Jan 22, 2019

Can be,if the 2 sensors are in different locations. Using a laser temp gun I've checked temps in several different places of a running engine. Such as thermostat housing, top of rad, bottom hose connection, front of head core plug and block core plug. The temps vary as much as 20* or more.

Derwud · Jan 22, 2019

Dennis H said:
View attachment 708812 I’ll check connections first. There is a large plug receiver new to the battery area since efi. Also put a high power Receiver in recently. I trickle it on occasion. On the subject of variations, the coolant read 151 on the aftermarket gauge and 171 on the Edelbrock tablet at the same time. Different take off points? Suffering from TMI these days.

Sorry, seeing the red reverse warning light makes me laugh.. My 13 yr old was in the car last night helping me and she started rowing the gears, and she says, Dad, I think the car is possessed. This red light comes on in Reverse and 4th.. Yes the car is possessed, but the red light is to tell you, you are in Reverse, and that is not 4th, but also reverse..

Derwud · Jan 22, 2019

Darter6 said:
Can be,if the 2 sensors are in different locations. Using a laser temp gun I've checked temps in several different places of a running engine. Such as thermostat housing, top of rad, bottom hose connection, front of head core plug and block core plug. The temps vary as much as 20* or more.

Also new sensor vs old.. I had two coolant gauges and dropped both sensors into boiling water and they were both off, both around 10 degrees lower..

wagonman · Jan 22, 2019

To bad you are not closer, we could use my Sun VAT60 and Snap-on scope to check the Alt wave form. There is a way to full field the alt to check for Max output, just dont do it for to long though or you will let the smoke out.

bearman · Jan 22, 2019

could just be a bad voltage regulator. full field it that will tell you if its the alt or regulator. down in phoenix 2 yrs max on batteries the heat just does them in. you might think about going one size larger on batt cables and main alt wire with the new efi stuff. just a thought

Dennis H · Jan 23, 2019

Took a DMM and made some measurements. Cold battery measured 12.6V. Started car and measured 15.2, then 14.8, then 14.2V.
Hot idle headlights on, AC, radio measured 13.2 at battery.
The EFI tablet always measured 0.4 to 0.6 lower than the DMM.
Probed a few spots under the hood. Difference from battery was never higher than 0.3V.
I’m calling it good for now. Thanks Billccm.

Crackedback · Jan 23, 2019

What was ouput off the alt charge stud with all the accessories live?

Ground it back to the battery neg when testing.

Billccm · Jan 23, 2019

Crackedback said:
What was ouput off the alt charge stud with all the accessories live?

Ground it back to the battery neg when testing.

Drop was 200 to 300mV

kiwigtx · Jan 24, 2019

Might be a little late to the party @Dennis H ...my ISP went down big-time last night while writing this....

Dennis, is the battery voltage readout generated from the EFI unit/throttle body?

If so, you are getting similar results to my truck setup. I m yet to try this experiment, but can you run a pair or wires direct from your battery into the car interior, and hook up a digital voltmeter, and take some readings again.

I am thinking (at least in my truck) that the heat of the throttle body when the engine is warmed up, is affecting the sensor which gives a voltage readout.

Hopefully you get what I am saying....I plan to do this very experiment myself in a couple of weeks.

I have seen the voltage readout in my truck drop to low 12's when hot from running....and yet the charge does not seem affected - I think it maybe just a sensor/heat issue - or in m y case, the alternator maybe getting overheated. Not a lot of room inside the doghouse of an A100.

It may not be an issue at all....just a readout issue on the EFI display.

LMK if that helps...I can do some testing in a couple of weeks for you as a comparison - BTW, I am running a Holley Sniper.

12.4 charge driving. Replace alternator?

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