full stop + brakes then go = dim light drag

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grahamscrackers

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Hello all and thanks for reading.

I have a 2007 Pontiac Montana sv6 3.9L with ~140,000km.
Base model
Transmission was rebuilt.
Spark plugs and wires replaced
Alternator replaced with 125 AMP. (was getting 13.5-15.7 volts, avg 15.3 and not charging the battery)
I bought it used.
New brake pads and rotors (and one caliper)
Belt is in good shape.
Brakes feel great, no fade issues or lack of braking power.

The problem.

When I come to a full dead stop with the brakes on, all is well. When I release the brakes to move forward my headlights pull down then come back up. 1 sec drop more or less. Voltage gauge in the dash shows a momentary drop to 13.x volts when back to 14.4-14.7 volts.


I'm completely stumped.
 
Have you had the battery load tested? Have you measured alternator voltage output with a hand held gauge?
 
@melsg5 - Regarding the battery. I replaced it about 1.5 weeks ago. All part of the work to 'fix' the issue. The new battery was load and charge tested at the shop where I bought it and again when the alternator was changed.

@Steelcity - Regarding the voltage regulator. I took the van with the 105AMP alternator installed to a shop here. They tested it and said it was fine. But the voltage on the dash showed out of spec. They still said the alternator and voltage regulation was working fine. I didn't agree. I went and bought a 125 AMP alternator from a parts shop here, good brand, and took it to another shop to have it installed. The new alternator output voltage is normal at 14.3 -14.8 volts (somewhere in that range). If I sit with the van in park or nuetral.... or just drive down the road I can put high beam lights on, fans on max, 4 way lights and wipers going and the new alternator + regulator voltage doesn't go below 14.3Volt.

The issue only presents when in drive or reverse engaged, at a full stop, and releasing the brake to move the vehicle in gear. Very mysterious.

Thank so for the ideas. Keep em coming!
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This is a long shot but.... I have heard of this causing problems although not very common, loose belt, or a worn out pulley tensioner ? I guess the alternator won't spin fast enough when under load ?
 
How about all your connections , clean and tight ? Battery cable in good shape not swelled up at the ends cause of corrosion ?
 
Belt and tensoner seem fine.

I'll have to check the battery cables. I didn't look at them before.
 
Steelcity said:
How about all your connections , clean and tight ? Battery cable in good shape not swelled up at the ends cause of corrosion ?
Click to expand...

Sometimes if this is the case, you will also get a slow crank on the starter, kind of like starving the system for amps .
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A thought on the belt.

I bought the van in 2009 I think. Its the same belt. However, in my ownership I've only put on ~12k km. The van sits with the odd trip to the hardware store. Its my Van-Truck.

A new belt is 40$.

I have some belt spray. When its warm out this weekend I'll try the spray and see if that makes any difference before I buy a belt.
 
make sure you check the battery cables at the other ends, the ground and the starter.
 
Little more thought.

Throttle body is dirty.
Air filter could be replaced, wasn't in the cleanest state.

I start the van in the driveway, put it in D, brake on, brake off, ... no lights dip. I repeat this for a minute... nothing.

I drive around the block, temps come up a bit, repeat the D / brake test over, lights dip.

Could this possibly be related to general need for cleaning (throttle body, air filter, fuel system etc)?
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Are u thinking any dip in the idle causes it? If so then could be any number of things related to a tuneup .
 
Well, a little more action and a little more observation.

1 - air filter replaced. idles a bit better
2 - Sea Foam spray cleaner (like the liquid you pour in but in a spray, same product). A little smoke but not bad.

Its old out here so my troubleshooting steps are brief.

While standing there doing the sea foam treatment I took advantage of the time and inspected wiring under the hood looking for things that stand out.

Something stood out.

Someone had has a remote starter installed into this van. I don't have any fobs. I know this ties into the shift position, brake light, hood close etc. So this could be the heart of my problem.

Today (-10) I drove to the hardware store and made another observation. When in D, 15.1 - 15.3 volts. But when in R, 14.8 volts. Changes the instant I engage the gear. This again, could be the old remote starter or the wiring of it if it was hacked out like I suspect.

Warmer weather is coming in the next few weeks. I'll investigate the remote starter install then.
 
have you checked the voltage output with a handheld gauge because those 15+ readings are too high, bad battery, bad connection, bad voltage regulator.
 
The 15+ volts only happens when the van is in drive.

I paid a mechanic to check over the power system, he said all was well.
He said the battery (new one I just put in) was shot. I replaced it again. This time the battery was tested before I installed it.

I had a different (trusted) mechanic replace the alternator anyway to be sure.

The alternator includes the charge controller. If the charge controller was the issue I would expect to see bad voltages all the time? Being as the issues remained for the new alternator & voltage regulator which makes this less likely to be the issue.

I'm leaning more toward the after market remote starter causing some issues. Unless, someone knows why voltage spikes to 15+ in D, but doesn't in N, R, Park regardless of brake pedal action, rpm, speed, temperature. I don't know of anything else D would be engaged for electrically that R wouldn't be except for the after market remote starter.

I'm hoping its just a bad connection to the remote starter unit(s) causing high resistance or something similar. I'll find out in a couple weeks when it warms up what the wiring condition of the remote starter (after market) is, all I can see to peek around is a mess.
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Okay!

I went out while waiting for my wife to get home and decided I was going to pull down the driver kick panel. Its down.

Oh my, mess. AutoFlex BBF remote start and some other black box that goes up to the steering column/wheel.

I poked along noting that much of the electrical tape right at the back or the harness where this 'person' decided to hack in, its lifting. I didn't look at all the wires, no time, to cold.

Still don't know if this is the problem but it is connected to many things. Turns out a bad ground on this can cause all kinds of problems. I'm going to ground it with a clamp and see if that changes things.

I also have a power leak somewhere, again something this aftermarket starter can cause. If the van sits for 2 or 3 days my battery drops to 11.x volts.
 
A small update.

80kmh drive 8.3 ltr/ 100km

110kmh drive 10.3 ltr/ 100km

The remote starter has been removed. I learned in the process of its removal that the bypass installed to these vehicles is literally an ignition key put into a box under the drivers kick panel. Open door, pull panel, open box, steal a GM, nice feature.

My voltage stayed high at 15.4 Volts for ~40 minutes. My battery was low from driving 3 and stopping several times over a couple week.

After this, my voltage has also stabilized at 14.3 - 14.8 volts.

During my out of town drive and back, my headlights also didn't dim at take off.

Now... the van has also dried out. No rain, no snow / ice melting off etc. So perhaps this is still an electrical problem in a dry spell.
 
Well,... thought I had it. Nope.

Van gets hot, van in D, brakes on (stop), brakes off... lights dip (including dash). Voltmeter will drop anywhere from .3 to 1.8 volts for a moment, then recovers.

When the van is running I can see voltages range from 15.5V down to 12.7 volts.

I'm going to research the grounding points on the vehicle and see if perhaps this is my problem.

The issue is best presented when the engine and transmission are hot, and its wet outside. Transmission shop cleared that the transmission isn't the cause today.

Ideas? Grounding points?
 
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