Location: Punta Gorda FL A Man's got to know his limitations!
Low voltage output from alternator
Installed a new race proven alternator and not getting the proper voltage. Alternator is new and battery is a new optima red top. Voltage is 10.5 at idle and 11.7 at 2000-2500 rpm. Any suggestions?
I've been told to check ground wires. Any suggestions are where they are located. Any help would be appreciated.
Do a search, there are a lotta posts about ground issues.
You also may want to look at posts subsribed by Bill Curlee, he always chimes in with help on various problems and often posts pics of what you are looking for. He chimed in on my last one on low voltage here:
Read the "sticky" above by Bill Curlee entitled "Important Electrical Infromation" -- shows you where all the grounds are. Do you have the correct pulley on that alternator??
Just remember this! The C5 electrical system is a 12 VDC system. All the modules require 12 VDC to operate correctly. They have a W I D E range of voltages at which they will tolerate and work in..
The PCM determines what the output of the alternator should be. So, if the PCM is happy at 13.1 volt output of the alternator, thats what you get. When you step on the brakes, turn on the HVAC FAN to HIGH ect..... and put a load on the charging system, the PCM has to see the drop in voltage and tell the alternator to increase output. This happens in fractions of a second but the delay is enough to cause a flicker in the lights and a movement on the gages.
If your seeing abnormal readings on the DIC or dash gage (what you perceive to be a LOW reading on the dash gages) put a voltmeter on the field terminal on the alternator and at the battery terminals and see what the ACTUAL readings are. You will be surprised in finding the actual battery voltages/alternator output is usually .5 to almost a full volt higher in some cases. So,,,,,,your 13.1 (which every one dreads seeing) is really 13.5 - 14.5.
What voltage does it take to CHARGE and or MAINTAIN the charge on a battery??? Its important to know that you don't need 14 -15 volts to maintain a charge on a battery! If the battery is fully charged and in good condition, it may only need 13.1 - 13.5 volts to maintain that charge condition and supply all the electrical stuff in your C5. If the battery gets discharged over a period of time, you may see 14.5 volts and as the battery charges, that voltage will slowly drop off to 13.1 to 13.5~ish volts.
The voltages that your seeing on the DIC and dash gages are NOT a TRUE voltage from the battery! As far as I can tell (GM does NOT show you what all goes on inside the dash cluster in the service manuals. ) there isn't a wire that hooks the gage meter DIRECTLY to the electrical charging system. The voltage readings comes from the PCM and goes to the IPC on a serial data line as a digital signal and gets interpolated as an analogue voltage. In fact, there are other displays on the dash that are interpolated from digital serial data buss signals.
So, if you want the SHORT VERSION of all of this is: connect a volt meter to the battery and compare it to the DIC/dash readings ! The one to worry about is the real readings using a hand held volt meter at the battery terminals.
Location: Punta Gorda FL A Man's got to know his limitations!
Quote:
Originally Posted by Bill Curlee
Just remember this! The C5 electrical system is a 12 VDC system. All the modules require 12 VDC to operate correctly. They have a W I D E range of voltages at which they will tolerate and work in..
The PCM determines what the output of the alternator should be. So, if the PCM is happy at 13.1 volt output of the alternator, thats what you get. When you step on the brakes, turn on the HVAC FAN to HIGH ect..... and put a load on the charging system, the PCM has to see the drop in voltage and tell the alternator to increase output. This happens in fractions of a second but the delay is enough to cause a flicker in the lights and a movement on the gages.
If your seeing abnormal readings on the DIC or dash gage (what you perceive to be a LOW reading on the dash gages) put a voltmeter on the field terminal on the alternator and at the battery terminals and see what the ACTUAL readings are. You will be surprised in finding the actual battery voltages/alternator output is usually .5 to almost a full volt higher in some cases. So,,,,,,your 13.1 (which every one dreads seeing) is really 13.5 - 14.5.
What voltage does it take to CHARGE and or MAINTAIN the charge on a battery??? Its important to know that you don't need 14 -15 volts to maintain a charge on a battery! If the battery is fully charged and in good condition, it may only need 13.1 - 13.5 volts to maintain that charge condition and supply all the electrical stuff in your C5. If the battery gets discharged over a period of time, you may see 14.5 volts and as the battery charges, that voltage will slowly drop off to 13.1 to 13.5~ish volts.
The voltages that your seeing on the DIC and dash gages are NOT a TRUE voltage from the battery! As far as I can tell (GM does NOT show you what all goes on inside the dash cluster in the service manuals. ) there isn't a wire that hooks the gage meter DIRECTLY to the electrical charging system. The voltage readings comes from the PCM and goes to the IPC on a serial data line as a digital signal and gets interpolated as an analogue voltage. In fact, there are other displays on the dash that are interpolated from digital serial data buss signals.
So, if you want the SHORT VERSION of all of this is: connect a volt meter to the battery and compare it to the DIC/dash readings ! The one to worry about is the real readings using a hand held volt meter at the battery terminals.
Hope all this helps.
BC
Thanks Bill. The alternator is the Halltech MD 90. It is rated at about 80-85 amps from what I was told by Race Proven Inc. It was used when Halltech designed the turbo system for the C5 and had to be used with the special bracket they produced. My pictures show the alternator and bracket. My car would start throwing codes and even shut down the dash lights and headlights. Voltage was down around 10 and less at idle and would not go above 11.5 at 2500 rpm. Could it be the amp rating? Race proven told me that the important number when charging is the volts, not the amps. Is this true and what would you recommend. I can find no ground problems and did not have this issue until I added this bracket and Alternator.
Expected voltage based on the unit you are running. This is what Halltech was getting also you talk to any of the PTK guys.....always low voltage....If the car runs fine and you have no problems ..dont worry about it. You can fit a larger ND 150 altenator as I did....but it requires multiple custom changes including head, valve cover, manifold, fuel rail, additional pulley (custom made) and a 1.5 inch diameter alternator pulley and custom brackets ....
on the whole "enough amperage thing" How many amps does a C5 require to operate?
Also why did some C5s come with the French 110 amp Valeo models and other got the mexican made 140 amp? Is there a difference in amperage requirements or was this simply seen as an upgrade through the years as having more power to play with?
Expected voltage based on the unit you are running. This is what Halltech was getting also you talk to any of the PTK guys.....always low voltage....If the car runs fine and you have no problems ..dont worry about it. You can fit a larger ND 150 altenator as I did....but it requires multiple custom changes including head, valve cover, manifold, fuel rail, additional pulley (custom made) and a 1.5 inch diameter alternator pulley and custom brackets ....
Tom
Tom
WHY in the world would would any one INTENTIONLY install an aftermarket alternator on a C5 that doesnt work ???
"Expected voltage based on the unit you are running. This is what Halltech was getting also you talk to any of the PTK guys.....always low voltage...."
Unless it can supply a solid voltage above 12.5 VDC, your NOT going to maintain a battery in a daily driven street car.
Location: Punta Gorda FL A Man's got to know his limitations!
Bill, They told me it should be putting out 13-14 volts. I sent one back and this is the second one. They assured me it was tested before it was shipped. I purchased the unit that utilizes the main alt. wire and they sent instructions to take the 3 wire connector, cut it off the harness and use the supplied 2 wire connector that fits on their alt. They advised to use the gray wire(FR) and the red(lamp) wire. They said the sense wire is not used. If Jim at Halltech is checking this thread, maybe he can shed some light also. I want the voltage to be correct and I don't think it is wise to just ignore it. Should I have bought the one wire alt.?
Bill
I think the twin turbo design wasnt thought through....the space where the alternator sits...upper passenger side....is space limited so the smallest alternator on the market was chosen.
I spoke to all the PTK guys...all complained of low voltage...yet none of us ever had a problem maintaining power to any accessory. This is real world testing....by multiple people......cant get better than that..
Also the ND model alternators are made for race teams that run high rpms....these things need to run at 10,000 rpm (based on pulley size) for one to get them to voltage /AMP output and for cooling purposes (this from the Race Proven builders....in Georgia and Germany).....they know alternators.....
Keep in mind we are not talking about a direct drivers side alternator replacement here is my setup....ND150 (160 amp output at 280 degrees and 16,000 rpm)...havent run the motor with this alternator...yet..
Location: Punta Gorda FL A Man's got to know his limitations!
Quote:
Originally Posted by Tomulrich
Bill
I think the twin turbo design wasnt thought through....the space where the alternator sits...upper passenger side....is space limited so the smallest alternator on the market was chosen.
I spoke to all the PTK guys...all complained of low voltage...yet none of us ever had a problem maintaining power to any accessory. This is real world testing....by multiple people......cant get better than that..
Also the ND model alternators are made for race teams that run high rpms....these things need to run at 10,000 rpm (based on pulley size) for one to get them to voltage /AMP output and for cooling purposes (this from the Race Proven builders....in Georgia and Germany).....they know alternators.....
Keep in mind we are not talking about a direct drivers side alternator replacement here is my setup....ND150 (160 amp output at 280 degrees and 16,000 rpm)...havent run the motor with this alternator...yet..
Tom
Tom
Tom, Since the pulley on this ND setup is half the size of the stock Valeo alternator, wouldn't it be spinning about twice as fast at the same RPM? I would think that if I'm running 2,500 rpm at cruise speed, it would be spinning as if it was running at 5,000 rpm, due to the reduced size of the puley. ?????
Also the ND model alternators are made for race teams that run high rpms....these things need to run at 10,000 rpm (based on pulley size) for one to get them to voltage /AMP output and for cooling purposes (this from the Race Proven builders....in Georgia and Germany).....they know alternators.....
Keep in mind we are not talking about a direct drivers side alternator replacement here is my setup....ND150 (160 amp output at 280 degrees and 16,000 rpm)...havent run the motor with this alternator...yet..
Tom
Tom
You'll have to let us know how that alternator does once you've run with it. My alternator (PTK) has started to get lower and lower voltages at idle and at lower rpms, forcing me to stare at that gauge way too much
If it works for you (or anyone else who's gone with another setup), I'll pick one up and really put it to the test. You'll have to give up more detailed info though on what changes/mods were needed to get that unit in there. If it can survive a year or so of underhood heat created by topmounts when subjected to 25minute HPDE's, It'll survive.
As for 11.7 at 2500rpm... there's something wrong there. When I first got my setup it would show > 13.5v at idle and 14v at anything above 1200rpm cold and 12 - 12.5 @ idle and 13.5 above 1.2k when hot. Now, which is at a point where it's degraded and I can't stand, it'll do the same when cold but after 10 minutes or so of running, it'll go 11.5 at a light and will go to 13v only when above 1800rpm. Confirm you're getting those voltages when your fans aren't running or when you've got AC on with inside fans blasting. With no load and those voltages, your battery isn't getting charged.
Location: Punta Gorda FL A Man's got to know his limitations!
Got the battery checked today and it's fine. Voltage is at 11.0 at idle and 11.5 at 2500 rpm. This is the second one sent by Race Proven. They don't have a clue what's wrong. I'm going to try and take it to Advance Auto Parts tomorrow and have a volt meter put on it to see what the true output is. I got a couple of codes. Don't know what they are for but here's a list:
Does anybody know what these are and how to correct them? Could the wiring instructions I received for the alternator be screwed up. I know there is a F(gray), Sense(red) and L(red) wire on the factory harness. Could they have gotten the two red wires mixed up and would this cause my charging problem?
Ok..................Lets try to logically figure this out!! First things first.. Charge the battery. After its charged, read the voltage at the battery terminals. What ever the battery reads, you should read the EXACT SAME voltage on the field terminal (large red wire) on the alternator!!! (engine OFF)
If you hadn't already done so... check voltage of alternator output (without it being connected to anything except the ign. wire) at the very least you could see if it matches the in-dash gauge. If you're using the wrong wire off the harness, you probably wouldn't see any voltage at it's terminal.
Location: Punta Gorda FL A Man's got to know his limitations!
Voltage at alternator with engine off was 12.9
Voltage when engine running at idle was 11.4
Voltage at 2500 rpm was 11.9
Voltage when I first started the car and drove to Advance auto Parts was 13.4 on the DIC. It stayed there for about 5 minutes then dropped to 12.4/12.2. This could be due to the battery starting to lose charge after I started running it. It was down to 11.5/11.7 while drove another 5 minutes. This is where it is at 2500 rpm unless I put the AC on and it drops to 11.2 volts. I'm putting another charge on it and checking the alternator terminal again. I can't imagine why Race Proven would sell me an alternator that I told them was going on my daily driver which is basically stock and that the only mod was the twin turbo. I don't know of anyone driving around at 10,000 - 16,000 rpm's as Tom's earlier post alluded.
Would putting a larger pulley on the alternator make any improvement?
Last edited by candapifer; 08-19-2007 at 04:54 PM.
Corvette Store
Low voltage output from alternator
If the battery is fully charged and in good condition, it may only need 13.1 - 13.5 volts to maintain that charge condition and supply all the electrical stuff in your C5. If the battery gets discharged over a period of time, you may see 14.5 volts and as the battery charges, that voltage will slowly drop off to 13.1 to 13.5~ish volts. 
As far as I can tell (GM does NOT show you what all goes on inside the dash cluster in the service manuals. 
) there isn't a wire that hooks the gage meter DIRECTLY to the electrical charging system. The voltage readings comes from the PCM and goes to the IPC on a serial data line as a digital signal and gets interpolated as an analogue voltage. In fact, there are other displays on the dash that are interpolated from digital serial data buss signals.
Voltage is at 11.0 at idle and 11.5 at 2500 rpm. This is the second one sent by Race Proven. They don't have a clue what's wrong.
I'm going to try and take it to Advance Auto Parts tomorrow and have a volt meter put on it to see what the true output is. I got a couple of codes.
