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Alternator or other problems?

Tiny
RAYSEEGER
  • MEMBER
  • 2006 CHEVROLET TRAILBLAZER
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 85,000 MILES
Out trailblaser check engine light comes on with a trouble code which says "engine RPM lower than expected" and has for a while. My wife has also complained that the headlights dim and brighten while sitting at a light for some time. She left it running one night with the lights on and the heater blowing for a while and the motor cut off with a dead battery. The vehicle runs fine otherwise by the way. The alternator charges fine until you turn electrical loads on while at idle, lights, rear defroster, or heater fan(but not any single one by itself)which will cause a discharge of the battery. If you bump the throttle it will go back to charging and then discharging.
Is the alternator bad or is something letting the rpm get low under electrical load conditions which is too low for the alternator to charge?
I believe the manual says rpm should be 550 which it idles at preety good but will dip below when you turn an electrical load on.
thanks
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Thursday, March 18th, 2010 AT 3:21 PM

15 Replies

Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Hi rayseeger, Welcome to 2carpros and TY for the donation

Get the alternator load tested if okay -you need to have the computer controlled of the field generation circuit/duty cycle checked out-see below Chargew system EWD


https://www.2carpros.com/forum/automotive_pictures/12900_c1_29.jpg




https://www.2carpros.com/forum/automotive_pictures/12900_c2_27.jpg

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Thursday, March 18th, 2010 AT 5:48 PM
Tiny
MOLOVE101
  • MEMBER
  • 1 POST
  • 2004 CHEVROLET TRAILBLAZER
  • 6 CYL
  • 65,000 MILES
I have a 2004 Chevy Trailblazer, and the battery gauge is showing an over charge. What can be the trouble?
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Monday, June 1st, 2020 AT 2:44 PM (Merged)
Tiny
ERNEST CLARK
  • MECHANIC
  • 1,730 POSTS
The voltage regulator may be bad inside the alternator. The alternator has to be replaced as a unit with the regulator.
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-1
Monday, June 1st, 2020 AT 2:44 PM (Merged)
Tiny
JSTARQUINO
  • MEMBER
  • 6 POSTS
  • 2004 CHEVROLET TRAILBLAZER
  • 52,000 MILES
For some reason when I turn on my defroster my 2004 Chvey Trailblazer dies. I replaced the battery thinking that might be it. I had my son in law bring his voltage meter over and tested the charging system. All is okay. Tested 14 1/2. All other positions on the heater works great. But when I turn on the defroster the car dies. Can you help?
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Monday, June 1st, 2020 AT 2:44 PM (Merged)
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Ac compressor locking up and stalling the motor?

See if this is what happens

Roy
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Monday, June 1st, 2020 AT 2:44 PM (Merged)
Tiny
JSTARQUINO
  • MEMBER
  • 6 POSTS
The problem is not with the A/C. It is only the defroster. All other positions on the heater vents work just fine
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Monday, June 1st, 2020 AT 2:44 PM (Merged)
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
In defrost, the ac compressor comes on for humidity control

Roy
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Monday, June 1st, 2020 AT 2:44 PM (Merged)
Tiny
JSTARQUINO
  • MEMBER
  • 6 POSTS
Husband wants to know why the A/C works perfect. And how do we test this ac compressor? I appreciate all your help
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Monday, June 1st, 2020 AT 2:44 PM (Merged)
Tiny
JSTARQUINO
  • MEMBER
  • 6 POSTS
Roy are you still there?
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Monday, June 1st, 2020 AT 2:44 PM (Merged)
Tiny
MCSWAIN1
  • MEMBER
  • 1 POST
  • 2003 CHEVROLET TRAILBLAZER
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 72,000 MILES
I have a noise coming from engine when engine is reved up when it is in idle it doesnt do it. The pulley for the water pump or fan u can wiggle a little I think its suppose to have some play in it because its not bolted straight to the engine block but I could be wrong. Ive took a long screw driver and stuck on or around each pulley and the loudest noise and vibration comes from alternator pulley. What may be ur take on this thank u for ur answer and your time. If anyone can help
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Monday, June 1st, 2020 AT 2:44 PM (Merged)
Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
Remove the serpentine belt, then spin the a/c, alternator and idler and tensioner pulleys, they should spin freely, with no bearing grind. At 72,000 you may need an idler or tensioner, Belt may be too loose, tensioner and belt should be changed.
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Monday, June 1st, 2020 AT 2:44 PM (Merged)
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Yes I am.

If the ac works in normal mode for ac, then my theory is wrong.

Is the check engine light on?

Roy
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Monday, June 1st, 2020 AT 2:44 PM (Merged)
Tiny
JSTARQUINO
  • MEMBER
  • 6 POSTS
Sometimes. But the guy at Chevy told me since the color is orange it means my gas cap isnt any good anymore. So, we replaced it and the check engine light went off.
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Monday, June 1st, 2020 AT 2:44 PM (Merged)
Tiny
JSTARQUINO
  • MEMBER
  • 6 POSTS
Roy, I must be having issues with my computer. It keeps telling me that internet exployer can not display the web page. I appreciate all your help and will probably have to take it to the Chevy mech. As they cut my hours at work, I have a feeling I'm gonna freeze for a while. Again thanks for your time.
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Monday, June 1st, 2020 AT 2:44 PM (Merged)
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
What is the code you got from the shop?

Roy
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Monday, June 1st, 2020 AT 2:44 PM (Merged)

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