Electrical Problems

I have a 2000 S10 Blazer 4.3L 4door LT. SInce I purchased the blazer I have noticed that the headlights, dash and anything attached to the battery dims then returns to normal. Had the alternator replaced and changed out 2 batteries and still no solution. I only nitice it at night and the dealership can't find the problem. Any Suggestions????

This is typical of OBDII vehicles with in excess of 20,000 miles on them. Though I am not sure, I believe that this is a software issue. Bear in mind that the PCM controls the charging voltage by varying the rotor current in the alternator. Yours is not the only OBDII vehicle I have seen do this. Chrysler, Ford, GM, and some foreign vehicles do the same thing. Ray

How do I prevent it from continuing. Some times while sitting at a light it does it and damn near stalls it

First of all you said that you took it to the dealership, and they couldn't find the problem. Let me say this, there are great techs at dealerships, and you and I are not even comparable to them. On an Intermittent problem it is hard for the tech to diagnose the problem. In order to fix this problem, he some how needs to duplicate it. Actually, you need to take it back to the dealership, and give them some time to check it, or take it to a shop with experienced techs.

You must be a mechanic or the spouse of one. DOn't worry, I'm not knocking the techs, its just more of a frustration towards the vehicle that after multiple attemps still hasn't been resolved. I have LOTS of friends who work as GM techs and they told me that one good solution to fix this problem to get rid of it. If I didn't own so much on it I would do so but I will just have to grit my teeth and hope that it works out

the problem you having with it could be loose main body ground or loose main power feed wires or loosing ign to alternator no way to know unless acting up

Is there anything else that it could be? I tried to center the problem towards what you had suggested and its still doing it.

is the lights flickers or they realy go dim and for how long

Here is some information about your concern

Info - Low Voltage Display on IP Gauge, Lights Dim at Stop Lights, Battery Discharged, No Start, Slow Cranking, DIm Lights at Idle, Low Generator Output #02-06-03-008 - (08/21/2002)
Low Voltage Display on IP Gauge, Lights Dim at Stop Lights, Battery Discharged, No Start, Slow Cranking, Dim Lights at Idle, Low Generator Output
1990-2003 Passenger Cars and Light Duty Trucks

2003 HUMMER H2

This bulletin is being revised to update the model years and to update text. Please discard Corporate Bulletin Number 43-64-07A (Section 6 -- Engine).

Any vehicle may have a low voltage display (if equipped with gauges), lights that dim at stop lights, slow cranking, no start, low generator output at idle or dim lights at idle when electrical loads are heavy at idle or under slow driving or infrequent usage conditions. These characteristics may be more noticeable with customer added electrical accessories, or with a discharged battery. These are normal operating characteristics of a vehicle electrical system and no repairs should be attempted unless a proven fault has been diagnosed.

During normal driving conditions, when engine speed is above 1000 RPM, the generator is designed to do two things:

Supply the current necessary to operate the vehicle's originally equipped electrical devices (loads).
Recharge/ maintain the battery's state of charge.
The following factors may affect generator and battery performance:

Non-usage of the vehicle for extended periods of time. The vehicle's computers, clocks and the like will cause the battery state of charge to drop (For example; 30 days in a parking lot and the vehicle may not start because of a dead battery or a vehicle which is driven to church only on Sunday may end up with a discharged battery to the point where the vehicle may not start). This would be considered abnormal usage of the vehicle and the normally expected result for the vehicle battery, generator and electrical systems.
At idle, vehicle electrical loads may exceed the low speed current (amperage) output of the generator and when this happens the shortfall comes from the battery. This will result in a drop in the electrical system voltage as the battery delivers the additional electrical current to meet the demand. This is equivalent to the brown outs experienced by homes and businesses when the electrical demand is more than the supply. See Figure 1.
Extended periods of engine idling, with high electrical loads, may result in a discharged battery. Attempting to recharge a battery by letting the engine run at idle may not be beneficial unless all electrical loads are turned "OFF".
Increased internal generator temperatures from extended idling can also contribute to lower electrical system voltage. As the generator's internal temperature rises, the generator's output capability is reduced due to increased electrical resistance.
The following are some typical examples of electrical loads:

System
Amperage Load

Rear Window defogger
25

Electric AIR Pump
25

Heated Seats
5 Amps per seat

Headlamps (high)
20

Blower Motor (High)
20

Headlamps (low)
15

Brake Lights
6

Windshield Wipers
6

Ignition
6





Depending on the vehicle application, generator current (amperage) output at engine idle speeds of 600-700 RPM can be as low as 35 percent of the full rated output. With enough electrical loads "ON", it is easy to exceed the generator current (amperage) output when the engine is at an idle of 600-700 RPM. This is a normal condition. The battery supplements for short periods of time. Items that affect the vehicle's electrical system current and voltage at idle are the number of electrical loads being used, including add-on accessories, and extended idle times. When the vehicle speed is above approximately 24 km/h (15 mph), the engine/generator RPM is high enough and the generator current (amperage ) output is sufficient to supply the current (amperage) requirements of the vehicle as originally equipped and recharge the battery.

Dimming lights at idle may be considered normal for two reasons:

As the engine/generator speed changes, so will the current (amperage) output of the generator. As a vehicle slows, engine/generator RPM slows, and the current (amperage) output of the generator may not be sufficient to supply the loads, the vehicle system voltage will drop and the lights will dim. Dimming of the lights is an indication that current is being pulled from the battery. If the battery is in a low state-of-charge (discharged condition), the driver will notice a more pronounced dimming than a vehicle with a fully charged battery.
When high current loads (blower, rear defogger, headlamps, cooling fan, heated seats, power seats, electric "AIR" pump, or power windows) are operating or cycled "ON", the generator's voltage regulator can delay the rise in output. This effect, usually at lower engine speeds, can take up to ten seconds to ramp up the generator output. This is done to avoid loading the engine severely. To increase current (amperage) output, additional torque is consumed by the generator. The engine computer (PCM) will ramp up engine/generator speed in small steps so engine speed variations are not noticeable to the driver.

It's almost as if I'm running subs and when the base hits the entire system dims headlights, dash lights everything but no sub systems to cause it. Do vehicle doesn't react at any certain speed it could be stopped at the light or going 85. There is a new problem that just started up but lets solve one at a time. Know anything about oil leakage???