Voltage regulator?

[JeepinDoug]

2004.5 CTD.
I just installed a Smarty touch which shows ECM-voltage at all times and it's running at 15 volts constant.
I have two red top optimas about 1.5 years old and the tops are bulging.
My stock volt guage is not moving at all, even when I shut the truck down. It's still at 14 volts.
The ECM-v guage on the smarty shows it moving a little but it doesn't climb any higher than 16v.

I need to assume the voltage regulator is failing even though it doesn't climb any high with rpm.

Do these alternators have the voltage regulator built in?
Or is the VR separated in the charging system.

 

[jhenderson]

No regulator. Voltage is controlled by the ECM. There are several things to check first. Disconnect both batteries and with a hand held meter check each bat separately. It could be you have one bad battery and the truck is trying to bring it up. It also can be the crossover cable having too much resistance. The truck senses voltage in th driver side batt and charges the pass side batt. If th cable is bad it won't charge the driver side properly. Lastly the batt temp switch under the driver batt may be bad, causing th truck to overcharge.

 

[JeepinDoug]

Thanks,
So the driver's side neg post clamp was loose enough to spin on the post. But I don't know how sensitive the system is to this.
There was no oxidation and I have yet to test drive it to see if gauges are working differently now.

Each battery checks 12.56v disconnected.

How do I check resistance in the crossover?
Since neither batteries are not under charged, I'd presume the crossover is good.

How do I check for a bad temp switch?
It seems more possible the batt temp switch would be bad since the symptoms lead to overcharging.

 

[Bob4x4]

ck for voltage drop-better than resistance test in many cases-don.t assume batteries are ok with just a voltage at rest number

 

[PWong]

2004.5 CTD.
shows ECM-voltage at all times and it's running at 15 volts constant.
The ECM-v guage on the smarty shows it moving a little

What's the ambient temp???
When it's COLD/FREEZING the ECM's target charging voltage was 15V.
When the driver side battery voltage was 0.05V or more off the target ECM would regulate the charging voltage.
I noticed 14.94-15.00-15.06V 99% the time on my ultragauge.
Once for while I noticed the reading overshot for another 0.05V.

 

[BILTIT]

My 03 runs at 14.7-14.8 when running all the time.

 

[AH64ID]

What's the ambient temp???
When it's COLD/FREEZING the ECM's target charging voltage was 15V.
When the driver side battery voltage was 0.05V or more off the target ECM would regulate the charging voltage.
I noticed 14.94-15.00-15.06V 99% the time on my ultragauge.
Once for while I noticed the reading overshot for another 0.05V.

Exactly. In cold temps ±15V is normal.

 

[JeepinDoug]

60-70s here in cali.
The volt guage is stuck or dead. Drop test when I get home from work.

 

[JeepinDoug]

All battery posts to clamps are good at 0v.

Alt pos to Driver's batt pos .036v

Alt pos to pass side batt .02v

Alt neg to Driver's batt neg .01v

Alt neg to Pass batt neg .009v

Does this look typical? I read somewhere I should worry at .5v but this is nowhere close.

I noticed one grid heater terminal was loose and oxidized. I'm gonna replace both of those once they arrive.

Even if 15v constant is within tolerance, they tops of my Redtop Optimas are bulging at each cell.
They aren't hot. They aren't puking gel at the vents.
The other big concern is the volt gauge not moving. It should atleast drop to 12.5v in acc position but it's stuck at 14v.

 

[PWong]

Thanks,
So the driver's side neg post clamp was loose enough to spin on the post. But I don't know how sensitive the system is to this.
There was no oxidation and I have yet to test drive it to see if gauges are working differently now.

Each battery checks 12.56v disconnected.

How do I check resistance in the crossover?
Since neither batteries are not under charged, I'd presume the crossover is good.

How do I check for a bad temp switch?
It seems more possible the batt temp switch would be bad since the symptoms lead to overcharging.

The driver side battery negative clamp was found loose, probably for a long time.
So the electrical connection was intermittently bad and hence the driver side battery voltage was intermittently lower than the target voltage. ECM would push up the alternator output charging voltage and hence both batteries got sign of overcharge.

The battery temp sensor under the driver side battery can be checked/cleaned and make sure it makes good physical contact with the battery.

 

[PWong]

60-70s here in cali.
The volt guage is stuck or dead. Drop test when I get home from work.

The target charging voltage should be 14.6-14.8V.

 

[AH64ID]

The dash gauge is an idiot gauge that is ECM controlled and not voltage controlled.

The touch can show charge voltage desired and ECM voltage. What are the two of them after driving for a bit?

If your crossover was loose it could cause a need for more charging as the ECM reads the drivers side voltage but the alternator connects to the passenger side.

Use the touch to check battery temp. After sitting overnight the battery temp, coolant temp, IAT, and EGT should all be within a few degrees.

Your battery temp sensor could be failing.

 

[dcgere2]

In the system relay box i found a30amp fuse that controls the flow it was blown now trying to find out why it keeps blowing as soon as i start the truck

 

[AH64ID]

In the system relay box i found a30amp fuse that controls the flow it was blown now trying to find out why it keeps blowing as soon as i start the truck

huh?

Controls what flow? The alternator needs more than a 30A circuit.

Did you post in the correct thread?

Are you talking about your truck or the OP's?

 

[dcgere2]

I was talking about this one he his is not charging and mine is doing the same thing and i followed the wire to the safety relay box under the hood and found that the 30 amp fuse between the postive and the big cable going to the alternator was blown. ..i replaced it and it started charging again until it blow again... now im trying to figure out why it keeps blowing out that fuse. .. all i was saying was for him to check that fuse maybe he is have the same problem im having. ...

 

[AH64ID]

He is charging, at 15V.

The alternator is a 136A alternator, so 30A won't cut it for a charge fuse. IIRC the Alternator has a fuseable link as the fuse for output.

You haven't stated what year truck you have, but on the OP's 04.5 the following are the 30A fuses in the main fuse/relay box.

Electric Brake
Ignition - Run only
Wiper Motor
FCM Power Feed
FCM Power Feed
Starter Solenoid

The FCM is the Front Control Module.

 

[JeepinDoug]

Got to play around with it today.
Swapped out two new heater grid relays.
One of the old ones seem to have a spinning post and I couldn't tighten it up very well.
Used dielectric grease, the push on terminals seemed a little loose so I crimped them down a little for a tighter connection.
When I started the truck the voltage fluctuated from 12.8 to 14.5 volts.
Once I drove around the voltage stopped fluctuating.
The dash volt gauge is still not working.
I'll monitor it for a few days.
Probably order a new battery temp switch just to see if it helps.
I don't know how well the BTS fits with the Optima battery being the battery
has a smaller footprint and I haven't looked to see where the switch is located
compared to the Optima.

 

[AH64ID]

Use your Touch to see the battery temp. There is no reason to replace that temp sender until you watch it and see if it's output is proper or not.

 

[JeepinDoug]

I didn't realize it can read battery temp, cool thanks.

 

[AH64ID]

Here is where mine was tonight. It was 43° out.

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