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Asked: Jan 26, 2008 - 06:30 PM

Status: Closed

after changing the battery in a 2002 chevy trailblazer when i turn on the heater the car has a rough idle

after changing the battery in a 2002 chevy trailblazer when i turn on the heater the car has a rough idle and will die

In Maintenance & Repair > Heating / Cooling
3 answers - 24 days ago

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kiawah

Date: Jan 27, 2008
Time: 09:28 AM

Turning on the heater, draws a relatively small amount of power to turn the blower motor. That normally should easily be replaced by the alternator, even if you had a weak battery. My guess is that you either have something putting a very heavy load on the engine, or the
electrical system is sooo weak, just the act of putting on the blower motor draws down the available voltage and the engine sparks become too weak.

I believe you need to do a little bit more work to get the problem symptoms isolated.
- Get the vehicle to an autoparts chain, where they can do a free alternator and battery check under electrical load. This will verify that your base car electtical power is eliminated as being a problem. Also be sure the battery and wire connectors are free from corrosion, and tight on the battery.
- On your heater, make sure that the heater selection is only on heat (no defroster or automatic settings where the A/C compressor would be energized). Heat only.
- If you turn your headlights on, does the engine die? They put a greater electrical load on the system than the blower motor.

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edward401

Date: May 23, 2009
Time: 07:47 AM

2002 Trail Blazer Battery Change: I have the very same issue - I changed my battery yesterday; now I have an idle problem that is associated with my air conditioner. My heater selection may also cause the same problem – I haven’t turned my heater on during trouble shooting.



History: No idle issues until batter change. This is the second battery for this car. With AC not selected idle is fine, 600 RPM. With AC selected, intermittently idle with drop to nearly 100 – 200 RPM then increase. Also – the car now can not hold cruise control selected speed precisely; speeds fluctuate -+ 1 mile per hour with RPM increase/decrease. With AC not selected during cruise, speed/RPM is rock solid as it has always been before the battery change.



Edward401us@yahoo.com

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fj4072

Date: Nov 01, 2009
Time: 01:41 PM

Disconnect your battery and clean the throttle body. Drive for a few miles with the AC off and let the computer relearn everything. This will cure your problem, very common in Trailblazers.

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