Car Voltage Reading

[GSR06]

Hi Guys,
I have one question that I would like all Sifus to give their valuable inputs. I currently have this problem which I don't have a clue on what the issue is.
Here it goes....
1) What should be the voltage reading at idling?
2) What should be the voltage reading when you switch on your air-con + head lamps?
3) Will the voltage drop when the air compressor kicks in?

My voltage is ~12+ v before I start my engine. After I start my engine, the voltage will increase to ~13 plus to ~14v (Remember that this is at idling). When I switch on my air con + head lamps, the voltage will drop to ~13v only. When air compressor kicks in, the voltage drops to ~12 plus v and sometimes, it dips below 12v at idling. When I press on the accelerator, the voltage increases again to ~13.9v (with air con + head lamps ON).

I actually changed a new altenator (APM, 75A) but the symptoms persist.

Is the above conditions normal during idling?

 

[DanzEterna]

does it effect your car?

 

[^pomen_GTR^]

what was your rpm during all that a/c on (compressor cut in)???

if below than 750rpm maybe u might need to increase a bit the rpm during load....

 

[amrancharger]

same symptom as my voltage reading.

but when the voltage drop there is no significant effect or the idle suddenly become high or low.everything seems to be normal.

but this really worries me, cuz planning a long journey of balik kampung.
dun wan me stranded in the middle of nowhere wif my family.

or shud i try removing the negative terminal at the battery while idle to check?
well i m scared if i do dat i might do more harm...huhuhu!

 

[yeehau86]

Hi Guys,
I have one question that I would like all Sifus to give their valuable inputs. I currently have this problem which I don't have a clue on what the issue is.
Here it goes....
1) What should be the voltage reading at idling?
2) What should be the voltage reading when you switch on your air-con + head lamps?
3) Will the voltage drop when the air compressor kicks in?

My voltage is ~12+ v before I start my engine. After I start my engine, the voltage will increase to ~13 plus to ~14v (Remember that this is at idling). When I switch on my air con + head lamps, the voltage will drop to ~13v only. When air compressor kicks in, the voltage drops to ~12 plus v and sometimes, it dips below 12v at idling. When I press on the accelerator, the voltage increases again to ~13.9v (with air con + head lamps ON).

I actually changed a new altenator (APM, 75A) but the symptoms persist.

Is the above conditions normal during idling?

My case:
1. Above 13V but below 14V
2. Drops a bit but never below 12V for a healthy situation
3. Yes, but just slightly

There was once my situation same as yours in my previous car where I have to press on the accelerator and the volt meter reading goes back up, but once on idle status, the voltage drops back to below 12V and my dashboard meters, digital clock, radio and aircond light starts to fade and my car barely dying off that I have to keep on revving the car on idle status infront of the traffic light. My case was due to alternator issue, once replaced this was solved, not sure about yours. Anything below 12V for me shows a bad sign of voltage.

 

[GSR06]

I am just afraid it might affect other parts later on and I just changed my alternator. BTW, do you know how much a new APM 75A altenator costs in the market?

does it effect your car?

---------- Post added at 07:31 PM ---------- 6 hour anti-bump limit - Previous post was at 07:29 PM ----------

My RPM hit above 1k during a/c on. I am monitoring now as the voltage will drop below 13v once compressor kicks in.

what was your rpm during all that a/c on (compressor cut in)???

if below than 750rpm maybe u might need to increase a bit the rpm during load....

---------- Post added at 07:34 PM ---------- 6 hour anti-bump limit - Previous post was at 07:31 PM ----------

Today, my voltage stays around 13.9~14.0v at idling and when I switch on the air con + head lamps, the voltage drops below 13v but not below 12v. Is this considered as an altenator problem as it is so called 'brand new'? Do you know if there is a device to boost the voltage or making the voltage more consistent?

My case:
1. Above 13V but below 14V
2. Drops a bit but never below 12V for a healthy situation
3. Yes, but just slightly

There was once my situation same as yours in my previous car where I have to press on the accelerator and the volt meter reading goes back up, but once on idle status, the voltage drops back to below 12V and my dashboard meters, digital clock, radio and aircond light starts to fade and my car barely dying off that I have to keep on revving the car on idle status infront of the traffic light. My case was due to alternator issue, once replaced this was solved, not sure about yours. Anything below 12V for me shows a bad sign of voltage.

---------- Post added at 07:39 PM ---------- 6 hour anti-bump limit - Previous post was at 07:34 PM ----------

Did you see the battery icon when you put on the ignition? If you don't see, then your altenator might have problem as it's the signal for altenator.

You can check your battery health at the batter shop. Voltage ~12v plus before you start the engine indicates a healthy battery. When you start your engine, the voltage should increase until 13v or 14v, depending on your altenator condition. Anything above 16v means overcharging and it is dangerous though. If your battery expanded physically, it means over charging.

My car's condition is different la...hard to describe. Would it affect the voltage if my air compressor is faulty?

same symptom as my voltage reading.

but when the voltage drop there is no significant effect or the idle suddenly become high or low.everything seems to be normal.

but this really worries me, cuz planning a long journey of balik kampung.
dun wan me stranded in the middle of nowhere wif my family.

or shud i try removing the negative terminal at the battery while idle to check?
well i m scared if i do dat i might do more harm...huhuhu!

 

[amrancharger]

i guess i haf to bring my car to my mech for checking.

the voltage before start is 12 and sometimes below 12volt...

 

[bera]

my voltage reading

12.4 before engine start
14.4 idle
14.0 when lights on or other electrical load then back to 14.4 after a while
13.0 lights + aircond (which i rarely use)

IMHO it depend on car to car...for example: stock car vs car had those high end ICE...

1 point worth mentioning to you is...before this my car have a few cables of grounding wire only...and the voltage fluctuates ranging from 0.5v to 1v...i notice after i install a set of grounding cables (ayam brand) the voltage is more stable...now rarely fluctuates..and if it does...it just 0.5v max...

as for your other concern about the alternator and such...a higher rating alternator doesnt directly solve your wattage issues...it just make charging more efficient...as all the charge generated are stored in the battery...

there is a lot of device in the market claim to increase/stabilize voltage output...pivot, hot inazama to name a few and some even diy their own stuff...just tepuk poket tanya wallet

 

[GSR06]

Did you observe the your dashboard lights going dim for a while when you turn on your air con? I am currently using the Pivot grounding (blue unit) but it still doesn't help much. In addition, your 13.0 is during idling or car running?

my voltage reading

12.4 before engine start
14.4 idle
14.0 when lights on or other electrical load then back to 14.4 after a while
13.0 lights + aircond (which i rarely use)

IMHO it depend on car to car...for example: stock car vs car had those high end ICE...

1 point worth mentioning to you is...before this my car have a few cables of grounding wire only...and the voltage fluctuates ranging from 0.5v to 1v...i notice after i install a set of grounding cables (ayam brand) the voltage is more stable...now rarely fluctuates..and if it does...it just 0.5v max...

as for your other concern about the alternator and such...a higher rating alternator doesnt directly solve your wattage issues...it just make charging more efficient...as all the charge generated are stored in the battery...

there is a lot of device in the market claim to increase/stabilize voltage output...pivot, hot inazama to name a few and some even diy their own stuff...just tepuk poket tanya wallet

---------- Post added at 09:11 PM ---------- 6 hour anti-bump limit - Previous post was at 09:11 PM ----------

Yes, better check now before it becomes serious... I am just worried about my ECU...

i guess i haf to bring my car to my mech for checking.

the voltage before start is 12 and sometimes below 12volt...

 

[bera]

yeah...but only dim a little...in my case ignorable...since the wattage reading from volt meter (measured using imitation pivot vcapa) only drop a bit...13v is when running...if idle and compressor kick in drop down to 12.5 plus minus...after a while will bounce back to 13...off compressor then reading climb back to 14v...never fall below 12v regardless of electrical load (radio + aircond compressor + radiator fan + lights)...

if you worry about ecu...then make sure the ecu fius (use proper rating as recommended)in good condition...so that if there any surge of current will cut the power to the ecu...

 

[teo1957]

I think if yours is an Evo you need to have either your ICV or your AFM sensor checked.

Once I had the same problem and I replaced the exact same thing first: alternator, thinking that it is an electrical supply problem. I found out that alternator is not the CAUSE, it's the EFFECT of irregular low RPM.

Irregular low RPM is caused by either faulty ICV or AFM sensor. Can go to workshop that have spares, swap and try. Or you can DIY clean using electronic contact cleaner: 30 minute job.

 

[jimmyae101]

normal if fan on during air on...rpm below 800 to 950 for different...if ur car rpm below 500 of coz underpower need acc a bit petrol...or serivce air filter,throolte body check spark plug...noramlly how much voltage on battery not really effect car performance,rpm important..idle how much and free idle how much...make sure rpm timing correct anything ok

 

[GSR06]

Almost same as my case... but my voltage fluctuates a lot. When I turn on the head lamps, the condition gets worst. Are you using normal head lamp?

yeah...but only dim a little...in my case ignorable...since the wattage reading from volt meter (measured using imitation pivot vcapa) only drop a bit...13v is when running...if idle and compressor kick in drop down to 12.5 plus minus...after a while will bounce back to 13...off compressor then reading climb back to 14v...never fall below 12v regardless of electrical load (radio + aircond compressor + radiator fan + lights)...

if you worry about ecu...then make sure the ecu fius (use proper rating as recommended)in good condition...so that if there any surge of current will cut the power to the ecu...

---------- Post added at 07:51 PM ---------- 6 hour anti-bump limit - Previous post was at 07:49 PM ----------

Bro, not an Evo la. My RPM looks ok and I guess my AFM is ok as well but I can further check later...

I think if yours is an Evo you need to have either your ICV or your AFM sensor checked.

Once I had the same problem and I replaced the exact same thing first: alternator, thinking that it is an electrical supply problem. I found out that alternator is not the CAUSE, it's the EFFECT of irregular low RPM.

Irregular low RPM is caused by either faulty ICV or AFM sensor. Can go to workshop that have spares, swap and try. Or you can DIY clean using electronic contact cleaner: 30 minute job.

 

[clanzkiller]

As far as i know, Voltage reading only indicate the weakness of the battery, operation of an alternator, and other electrical supply. It doesn't really affect performance, but some claimed that good earth grounding increase performance.
Scenario is baseless, alot of things can cause voltage to drop or fluctuated.

Related
1. Weak/Old battery
2. Alternator dieing soon
3. Bad earth grouding
4. Short-circuit
5. Audio system
6. Usage of electrical supply

Unrelated
1. Low RPM
2. When starting where starter required lot of energy to light the ignition.

This is what i can think of at the moment :)

 

[GSR06]

Scenario is baseless but if you don't share, it is also meaningless

Bro, could you share yours or not? If there is a problem, we need to troubleshoot lor. Anything can go wrong but we need to find out exactly what goes wrong but I know it will take time...

As far as i know, RPM reading only indicate the weakness of the battery, operation of an alternator, and other electrical supply. It doesn't really affect performance, but some claimed that good earth grounding increase performance.
Scenario is baseless, alot of things can cause voltage to drop or fluctuated.

Related
1. Weak/Old battery
2. Alternator dieing soon
3. Bad earth grouding
4. Short-circuit
5. Audio system
6. Usage of electrical supply

Unrelated
1. Low RPM
2. When starting where starter required lot of energy to light the ignition.

This is what i can think of at the moment :)

 

[clanzkiller]

Scenario is baseless but if you don't share, it is also meaningless

Bro, could you share yours or not? If there is a problem, we need to troubleshoot lor. Anything can go wrong but we need to find out exactly what goes wrong but I know it will take time...

Yeah bro. What I meant is that, you cannot assume that for example, inadequate/fluctuation of voltage is due to battery itself only or some other particular factor. As for letting ppl know your problem, u need to at least list out all the things that is relevant to voltage. Like any recent upgrade/changes, or whatsoever. So it will be easy to pinpoint the exact culprit.
As if u would like to know my reading, I got 3 devices to monitor my voltage, cause I got the digital voltage with fuse cheap so I just used it in replacement of my fuse. 2 will be 2-1 fuse digital, and a hks type-1 turbo timer.
I would give numbers based on the hks tt since I always
Monitor it instead of open my trunk and bonnett to check voltage reading.

Before ignition, 12.8-12.4, fans ran in 11.3-11.6
When starter work and ignite, drop til 9.xx
Engine running, without ac 14.2-13.8
On ac, compressor on, ac fan off, 13.6-12.8
On ac, compressor on, ac fan on, 11.2-12.6 --> 12.8-13.4
All ac component on, audio on, 12-12.8 --> 13.2-13.8
Car moving with all ac component on, audio on, 14.2-13.6
Ac off audio off, 13.8-14.2

And by this also. It have to depends on what battery u using, what type of fan, ac, engine, etc etc. Is so hard to compared unless both same car same mod. Then from there u can differentiate otherwise
Is really so hard. Hope u get what I meant.

 

[hksp]

all new toyota max charging voltage never over 13.8v, to prolong the battery life, this sux

old one can get to 14.2-4 idle

 

[GSR06]

Thanks for sharing bro. Really appreciate it. You don't hv issue when your voltage drops below 12v meh?

Yeah bro. What I meant is that, you cannot assume that for example, inadequate/fluctuation of voltage is due to battery itself only or some other particular factor. As for letting ppl know your problem, u need to at least list out all the things that is relevant to voltage. Like any recent upgrade/changes, or whatsoever. So it will be easy to pinpoint the exact culprit.
As if u would like to know my reading, I got 3 devices to monitor my voltage, cause I got the digital voltage with fuse cheap so I just used it in replacement of my fuse. 2 will be 2-1 fuse digital, and a hks type-1 turbo timer.
I would give numbers based on the hks tt since I always
Monitor it instead of open my trunk and bonnett to check voltage reading.

Before ignition, 12.8-12.4, fans ran in 11.3-11.6
When starter work and ignite, drop til 9.xx
Engine running, without ac 14.2-13.8
On ac, compressor on, ac fan off, 13.6-12.8
On ac, compressor on, ac fan on, 11.2-12.6
All ac component on, audio on, 12-12.8
Car moving with all ac component on, audio on, 14.2-13.6
Ac off audio off, 13.8-14.2

And by this also. It have to depends on what battery u using, what type of fan, ac, engine, etc etc. Is so hard to compared unless both same car same mod. Then from there u can differentiate otherwise
Is really so hard. Hope u get what I meant.

---------- Post added at 08:10 PM ---------- 6 hour anti-bump limit - Previous post was at 08:08 PM ----------

I thought of 15v is considered as over-charging?

Considering your total usage is high, then you might not have sufficient voltage to re-charge your 12v battery wor.. true or not?

all new toyota max charging voltage never over 13.8v, to prolong the battery life, this sux

old one can get to 14.2-4 idle

 

[clanzkiller]

Thanks for sharing bro. Really appreciate it. You don't hv issue when your voltage drops below 12v meh?

It only dropped below 12v when before ignite and during ignite, but never drop til 12v after ignite, and all electrical supply start-ups example lights, audio, etc..

Is normal for a vehicle that it wil drop til very low during ignition due to the high power supply to push the starter and turn the engine to a running condition. My fans run before ignition even a cold start, is due to the well-famous fan for evos. so i don bother it much. As long as the voltage while running maintain below 12, then i supposed everything is fine.

Sorry i had change the voltage reading on my previous post, i input the amount wrongly..

 

[dreamZz]

hi sifu,
my battery light no longer display. battery light suppose to show before car started but now it light was off and after started oso off(whc consider normal) now my voltmeter before atart 12.0-12.5 once started 13.0-14 driving fluctuating 13-16v which really worrying me. this scenario happen after i adjust the nut to increasing my car timing. over 16v on the road consider danger?? tq