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Voltage Drop At Every Stoplight

rlefeve

By rlefeve
in Ask A GM Technician

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rlefeve New Member

rlefeve

Posted
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I have a 2003 Sierra 1500HD. A few months back I started my truck and it acted like a low battery, but it started.

The next morning, I could not start it. I took the wifes car to work and tried it again after my shift was over. It started.

It ended up not starting on me again so I replaced the battery. That was not the fix so I replaced the alternator.

It starts strong and has not failed me but now when I am at a light or stopping for one reason or another the battery guage drops down to 9 or below and the truck runs really sluggish then slowly recovers, and occasionally stalls.

The cables all look good, I looked for a corrosion but found none. I know electrical problems can be a bear to deal with, has anyone experienced this?

One other thing, it is intermittent, I can always tell if it will happen as my gear shifter indicator is very dim.

GMstrong Enthusiast

GMstrong

Posted
Posted

Usually surging will drop voltage and usually stall.Do you have a rough idle?Does she fall on its face?Could be a simple brake switch.Could be a bad tps sensor.Does it make a clicking when you press the brake pedal?.Theres a verity of things it could be my suggest is to start with the smallest thing possible such as the brake switch see if it makes a clicking when you press it down and release it.

rlefeve New Member

rlefeve

Posted
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Posted

It does idle rough, but intermittenly. I will report back about the brake switch.

However I have more to add, not sure if it is relevant.

I seem to get a lot of clicking under the hood which I assume is my air conditioning compressor short cycling.

 

When I was troubleshooting my alternator/battery. I would let it run then remove the negative battery terminal to see if the alternator could keep it running and i hear the click followed by a stall.

 

my truck is loaded with power sucking features so when I turn on the seat heat, defroster......it acts up.

There were two alternators available for my truck, i do not recall the amperage but it was the recommnedation to go with the lower amperage alternator form the parts counter person. It might be as simple as needing the big dog alternator.

Frankhenrylee Enthusiast

Frankhenrylee

Posted
Posted

My truck does this same thing but not as often. I noticed the other day that something does click in the dash around the column when I push in on the brake pedal to shift it out of park. Once I'm in gear it doesn't click. What does the brake switch do and how do I replace it?

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