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Discussion Starter #1
Well, battery died and more than likley took alternator with it (at least I think....not sure). Replaced battery on Saturday. I also purchased a rebuilt alternator as well. Installed new battery, but voltage readings were low (ranged from 12.9 - 13.2 v). So installed the re-built Alt but readings were even worse (as low as 12.2 V and no higher than 13.2 v). Took 1st new alternator back and they checked it and confirmed that it woudn't hold voltage under load. Purchased a second alternator on Sunday and installed. Voltage readings (12.8-13.2 v) still seem low to me. I'm positive that just last week I had readings of 14.0-14.2 v from scan gauge. So, I took the 2nd alternator back and got a third one (currently installed). Readings are 12.8-13.2 v. No higher. I'm at a loss. I even took the battery back and had them perform a total batery load test (including individual cells) just to absolutley rule out battery. It checked out fine. So......I'm on my way over to pick up a 4th alternator.

Questions:
  1. What should volatge reading be? I've always thought that it should be a min of 14 V when car is above idle. If not, I don't think alternator would be able to properly charge the battery. Static readings on battery are at 12.5v. If not above that.....it won't even re-charge.
  2. I want to confirm that the only item control voltage output is the internal regulator on the alternator. PCM has no input on this right??
  3. Your thoughts??
 

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Discussion Starter #2
QUOTE (92MTXSHO97V8SHO @ Mar 23 2009, 12:41 PM) index.php?act=findpost&pid=711448
You know the old saying. "Car won't start, make sure it has gas".

Are the battery cables in good condition? Are all the rest of the grounding wires in good condition. .2 of a volt drop here and there across poor connections adds up. You did say you were getting 14.4v not long ago. Are the battery connections nice and clean? Is the battery cable running to the starter well connected?

Sounds like it is something very simple. I have not seen a voltage regulator that was outside of the alternator in a long time. Good luck[/b]
Cables are clean. terminals are new. Very clean.

I could see drop's in current over poor connections, but not voltage. I can't think of anything else that would be "in series" that would cause a drain on the voltage of an entire volt.
 

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A good alternator/regulator should put out 14.4V. As they age the voltage output will drop. Once the output is below 13.5V it's time to think about changing it.

The battery should have nothing to do with it. If the battery is so bad it pulls down the alternator voltage to the levels you are seeing then the alternator would be putting so many amps into the battery it will be gassing like crazy.
 

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I guess I should ask what rpm are you running to get that voltage? Goose the engine up to a steady 1500-2000 rpm and check the volts then.
 

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Discussion Starter #5
I'm right there with you.

I just put the 4th new alternator on it. Same results. 13.0 -13.2 v. This is at 1500-2500 RPM's.

The car runs fine. EVERYTHING is working. I've checked, pwoer windows, locks, A/C, blower fan, lights, cruise control, rear defog, radio, etc...EVERYTHING. Gauges are up and fine. No DTC's.

At idle, with lights on, A/C on, rear defog, blower fan on high, each alt has been outputting 75-90 AMPS (we have a big Snap-On AVR). I'm at a complete loss. :banghead:

Thank goodness we have a god parts dealer here in State College PA (Miller autoparts). He let me try two different Motorcraft Re-man alt's at no charge. No better results than my old alternator. So.....I re-installed my old one for the time being.

HELP!
 

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I just replaced my alternator with a brand new one. It puts out about 14.4 Volts. My problem is that this alternator gets very hot. I mean you could cook eggs on top of it. I cannot believe it has bad bearings already, since it is new. Sorry about hijacking this thread, but the discussion on the alternators got me thinking.....
 

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Discussion Starter #7
All 5 of the alternators that I have are super hot. I'll have to check it with my non-contact temp gauge when I get home. Be lucky that you don't have my problem.

I'd try a new one (haven't done that yet).....but they are bloody expensive ($270 for a Motorcraft).
 

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Discussion Starter #8
Does anyone know where I can get a copy of the wiring diagram for the charging circuit??
 

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Anyone that has access to "Ford Fleet" Internet service can get copies of any Ford schematic or parts system via the Internet.

Pictures are always worth 1,000 words and good schematics are worth even more than that. I will check at work tomorrow.

92SHO97SHO
 

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Discussion Starter #10
UPDATE:

I checked the wiring back between the positive battery terminal and the Altenator with OHM meter. I got ~4.0 ohm's resistance.....hmmmm. :eek: That's probably NOT GOOD! So I got looking around, and discovered when I checked resistance on the wire between the altenator and the fuse block that it was only 0.3 ohms.....hmmmmm. Turned out, that I had a build up of something between the 175 Amp bridge on the fuse block and the cables themselves. Disassembled and cleaned with dremmel wire wheel. re-assembled and checked resistance........0.3 ohms. Now that's better. :)

Readings are now consistantly at 13.3 v steady. So, I'm sure that was part of the problem, however, I'm not out of the woods yet.

Now, tomorrow I'll be calling NAPA to see if I can get the internal regulator for my current (old) Altenator. Bearings are all good. I'm pretty sure that the brushes come with the regulator kit....so I am very optimistic that should solve problem (and it should be a lot cheaper too).

An interesting phenomina.....any standard voltage gauge will read 13.3 V across battery terminals and just about anywhere under the hood, however, my Scan Gauge only reads like 12.7 V??? :angry: Anyone have any ideas with regard to that??
 

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Discussion Starter #11
QUOTE (trainguy1989 @ Mar 23 2009, 02:30 PM) index.php?act=findpost&pid=711491
I just replaced my alternator with a brand new one. It puts out about 14.4 Volts. My problem is that this alternator gets very hot. I mean you could cook eggs on top of it. I cannot believe it has bad bearings already, since it is new. Sorry about hijacking this thread, but the discussion on the alternators got me thinking.....[/b]
I forgot to check temp on Altenator......but I can tell you it's normal that they are smoking hot. If I remember, I'll take a reading. Wear gloves when removing one that is hot!
 

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QUOTE (herrhaus @ Mar 23 2009, 10:56 PM) index.php?act=findpost&pid=711671
QUOTE (trainguy1989 @ Mar 23 2009, 02:30 PM) index.php?act=findpost&pid=711491
I just replaced my alternator with a brand new one. It puts out about 14.4 Volts. My problem is that this alternator gets very hot. I mean you could cook eggs on top of it. I cannot believe it has bad bearings already, since it is new. Sorry about hijacking this thread, but the discussion on the alternators got me thinking.....[/b]
I forgot to check temp on Altenator......but I can tell you it's normal that they are smoking hot. If I remember, I'll take a reading. Wear gloves when removing one that is hot!
[/b][/quote]
Well that makes me feel better. Thanks
 

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I believe the 2003 and up are PCM controlled alternators. An alternator will get too hot o hole onto doing it's regular job.

The typical newer car will take ~50 amps just at idle with the AC off.
 

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QUOTE (herrhaus @ Mar 23 2009, 08:09 PM) index.php?act=findpost&pid=711607
UPDATE:

I checked the wiring back between the positive battery terminal and the Altenator with OHM meter. I got ~4.0 ohm's resistance.....hmmmm. :eek: That's probably NOT GOOD! So I got looking around, and discovered when I checked resistance on the wire between the altenator and the fuse block that it was only 0.3 ohms.....hmmmmm. Turned out, that I had a build up of something between the 175 Amp bridge on the fuse block and the cables themselves. Disassembled and cleaned with dremmel wire wheel. re-assembled and checked resistance........0.3 ohms. Now that's better. :)

Readings are now consistantly at 13.3 v steady. So, I'm sure that was part of the problem, however, I'm not out of the woods yet.

Now, tomorrow I'll be calling NAPA to see if I can get the internal regulator for my current (old) Altenator. Bearings are all good. I'm pretty sure that the brushes come with the regulator kit....so I am very optimistic that should solve problem (and it should be a lot cheaper too).

An interesting phenomina.....any standard voltage gauge will read 13.3 V across battery terminals and just about anywhere under the hood, however, my Scan Gauge only reads like 12.7 V??? :angry: Anyone have any ideas with regard to that??[/b]
The Scan gage may be reading the voltage at the PCM. This is probably regulated and constant? FWIW the hardware does the same thing.
 

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i would say test direct on batt not trought the pcm

and i bought a brand new alternator for 400 $ here at canadian tire and they are new from hitachi and i get lifetime warrenty on it

and im getting 13.8 14.0 steady

even on load lol it drop 13 on heavy load and it good for 130 amp bu twas tested to 155

but chekc voltage on batt not trough pcm

and secondly rebuilted alternator mostly have a old regulator in there they where not replaced since it was good to begin with

never again will i buy a rebuillted alternator replace mine 6 time before i went and bought a new one
 

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Discussion Starter #16
QUOTE (SHOZ123 @ Mar 24 2009, 12:09 AM) index.php?act=findpost&pid=711694
I believe the 2003 and up are PCM controlled alternators. An alternator will get too hot o hole onto doing it's regular job.

The typical newer car will take ~50 amps just at idle with the AC off.[/b]
Are you sure that it's a PCM controlled altenator? The Altenator has an internal voltage regulator on it. In fact I'll be calling around today to see if I can find a new one. Why would it have a voltage regulator if it was PCM controlled?


Oh, BTW, reading this morning were 14.0 - 14.3 v. Go figure! Even on my Scan gauge.
 

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This is from the 2002 service manual.

Principles of Operation

Charging system

This vehicle is equipped with a powertrain control module (PCM) controlled charging system. The PCM controlled charging system is a system whereby the PCM determines the optimal voltage setpoint for the charging system and communicates this information to the voltage regulator. The PCM controlled charging system is unique in that it has two unidirectional communication lines between the PCM and the generator/regulator. Both of these communication lines are pulse-width modulated. The generator communication (GEN COM) line communicates the desired setpoint from the PCM to the voltage regulator and the generator monitor (GEN MON) line communicates the generator load and error conditions to the PCM. The third pin on the voltage regulator, the A circuit pin, is a dedicated battery voltage sense line.

Circuit Description

B+ Output Terminal Circuit 36 (YE/WH)
Generator output voltage is supplied through the battery positive (B+) output terminal on the rear of the generator to the battery and the electrical system.

Circuit 1182 (OG/YE)
This is the A terminal battery voltage sense circuit and is used to sense battery voltage.

Circuit 3990 (LB/RD)
This is the generator communication (GEN COM) circuit. The PCM determines the optimal voltage setpoint for the charging system and communicates the information to the voltage regulator via the GEN COM circuit.

Circuit 1181 (GY/YE)
The generator monitor (GEN MON) circuit communicates the generator load and error conditions to the PCM. The PCM will turn on the charging system warning indicator if there is an error condition.
 

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Discussion Starter #18
THANK YOU! :thumb:

This more than likley explains why my Scan Gauge was displaying different voltages than actual readings under the hood. I would assume that the Scan Guage is not actually measuing voltage, but rather simply displaying the data that is going thru the PCM. I'm going to print this and give it some more thought. I'm apparently having an intermittant problem between the PCM and the Alternator.....probably some more cleaning of electrical connections.

People have asked me why I spend time working on vehicles.....this is why. You learn something new each time.

You are good man taking the time to look this up! Again, thank you.
 

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oh and youre gonna see different voltage since if the batt is fully charged the computer will say to stop
charging since the abtt is full but this morning the batt had some use and you started the car and being there overnight there is a small drain

so im sure all this is pretty good

the best would be to turn light on adn let the car off for 5 min or so then start the car the alternator should give you a nice 14 V to recharge the batt and when done it will drop to 12.6 13 same as my friend mazda there is nothing to be scared about

it normal
 
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