Low Voltage at idle
Thread Starter
Racer
Joined: Sep 2002
Posts: 270
Likes: 1
From: Torrance California
Low Voltage at idle
When I first start my car my voltage reads 14.2, then after a few minutes or when the idle goes down to 600 rpm the voltage drops down to 12.0 and lower. But with just a slight increase of about 50 more rpms (650 rpm at idle) there is no problem.
I replaced the alternator and still the same problem. I even tried different size pully. Is there any way to adjust the idle, or is controlled by the computer? :confused:
I replaced the alternator and still the same problem. I even tried different size pully. Is there any way to adjust the idle, or is controlled by the computer? :confused:
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Re: Low Voltage at idle (1SLO POK)
600 rpm is too low for idle. Also, at this low an rpm, the alternator cannot generate high enough output voltage to charge the battery so the battery picks up the load and this is why you see such low voltage. Your idle speed needs to be set higher.
Thread Starter
Racer
Joined: Sep 2002
Posts: 270
Likes: 1
From: Torrance California
Re: Low Voltage at idle (jfb)
Yes, I do have the underdrive pulley. Is there anything I can do to raise the voltage and still keep the pulleys?
How do adjust the Idle for highher RPM. I thought the computer chip did the setting. I do have a after market chip.
[Modified by 1SLO POK, 5:52 PM 9/14/2002]
How do adjust the Idle for highher RPM. I thought the computer chip did the setting. I do have a after market chip.
[Modified by 1SLO POK, 5:52 PM 9/14/2002]
Le Mans Master
Joined: Dec 1999
Posts: 8,540
Likes: 1
From: And on the fifth day, subpoenas were served to Obama senior staff
Re: Low Voltage at idle (1SLO POK)
See if you can get an undersized alternator pulley.
You can get a chip programmed for a higher idle.
You can get a chip programmed for a higher idle.
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Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: Low Voltage at idle (1SLO POK)
No problem, I had a similar symptom till I replaced my alternator and had the shop install the overdrive pulley onto the alt. Now I have 13.7 Vdc at cruise and 12.6 Vdc at idle of 600-700rpm.
The March P/N is #110 for the overdrive alt pulley; it's a 6-rib unit for '84-'87 Corvette. You can likely order it through Summit Racing.
This pulley matches up with the P/N 4101 underdrive crank pulley from the P/N 4435 Power & Amp Series pulley set from March. These pulleys are black power coated steel.
Tell the Tech at Summit that these are March numbers, not Summit ones.
The March P/N is #110 for the overdrive alt pulley; it's a 6-rib unit for '84-'87 Corvette. You can likely order it through Summit Racing.
This pulley matches up with the P/N 4101 underdrive crank pulley from the P/N 4435 Power & Amp Series pulley set from March. These pulleys are black power coated steel.
Tell the Tech at Summit that these are March numbers, not Summit ones.
Thread Starter
Racer
Joined: Sep 2002
Posts: 270
Likes: 1
From: Torrance California
Re: Low Voltage at idle (65Z01)
No problem, I had a similar symptom till I replaced my alternator and had the shop install the overdrive pulley onto the alt. Now I have 13.7 Vdc at cruise and 12.6 Vdc at idle of 600-700rpm.
The March P/N is #110 for the overdrive alt pulley; it's a 6-rib unit for '84-'87 Corvette. You can likely order it through Summit Racing.
This pulley matches up with the P/N 4101 underdrive crank pulley from the P/N 4435 Power & Amp Series pulley set from March. These pulleys are black power coated steel.
Tell the Tech at Summit that these are March numbers, not Summit ones.
The March P/N is #110 for the overdrive alt pulley; it's a 6-rib unit for '84-'87 Corvette. You can likely order it through Summit Racing.
This pulley matches up with the P/N 4101 underdrive crank pulley from the P/N 4435 Power & Amp Series pulley set from March. These pulleys are black power coated steel.
Tell the Tech at Summit that these are March numbers, not Summit ones.
That was it! :D Voltage is at 13.2 at 600rpm. Im amazed on how small the pulley is.
Thank you for that info, you were a great help. :cheers:
Dean
[Modified by 1SLO POK, 11:39 PM 9/19/2002]
Instructor
Joined: Dec 2001
Posts: 187
Likes: 0
Re: Low Voltage at idle (1SLO POK)
I remember when I had a voltmeter on my battery at idle showed 14.3 and the dash indicated 13.9... This was after I replaced the battery and alternator. I thought that when an engine is running the volt should be between 13.9 and 14.3?
1994, 85, alternator, c4, chip, corvette, dash, forum, high, idle, low, performance, problem, pulleyslow, showing, underdrive, voltage
