drewallen42

I've noticed when I start my truck the battery gauge drops down, the fan slows, the lights dim, and then everything comes back on as normal. The gauge goes back up and then a few seconds later it does it again. There are sometimes when I hit the gas everything comes back on normal and there are sometimes everything is normal and when I hit the gas everything dims.

I'm assuming this is a battery issue but just want to ask. The truck is only driven about once a week and then 10-12 times a year pulling a toyhauler.

If it is the battery do I need to check both or is there one to check first?

Thanks.

coolbreeze

No doubt your engine grid heater working. Its all in your owners manual.

dj88382000

posted in the 5.9 section but still the same thing Voltage Drop / Lights Dimming on Cold Start

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It's time to "sticky" this one at the top of the forums again.

If this describes what you're experiencing when lighting off the Cummins on these frosty mornings,.......
Don't worry, it's normal.

The Cummins uses a pair of 12 volt grid heaters in the intake tract
(imagine two large toaster elements glowing bright red)
that preheat incoming air for easier combustion.
The Ford & Chevy use glow plugs inside the combustion chamber.
As the relay cycles the grids on & off, the large amp draw causes the volt meter reading to drop, and the lights to dim when the relay turns on the juice.
The relay timer will turn off the heaters when the intake temps hit a preset limit, or when the vehicle exceeds a preset MPH (usually between 15-25 mph). edit


Don't panic

Swarthy Dago

I would think a battery also acts as it's own regulator, if a battery is bad or almost bad, might be worth it to just ck it out. charge it, put a load tester on it, look at the lead plates see how much of the white deposits have formed on the plates. Could that cause the off and on dimming too ?

chrigu

but i have the same without the grid heater!!!

the voltage drop down for 2-3 minutes....

but i have disconnected the heater.

jferg711

My truck does the same thing but when i start mine the battery guage drops lights dim and then like 2-3 secs later it comes back up then goes back down after i touch the gas, or wait like 3-5 secs and it goes back down. It does this like 6-7 times then stops.

thecatsfan

Just my $.02, but if you are able to cycle your grid heater, and then still have the juice to start the engine when it is cold, your batteries are probably okay. They do take a little while to recover because the grid heater cycle combined by immediately cranking a cold engine is a pretty significant draw. And the grid heaters continue to cycle during warmup. They can definitely draw the coltage down a bit.

But when my 01 had one battery go marginal on me last November, I couldn't even get the truck to start when it was cold and had to do a full grid heater cycle. It would fire the grid heater, but then would not have enough reserve power left to turn the engine over. I had dual Optima Red Tops at 750 CCA each, and one of them tested good. The other was not totally dead, but marginal at best. I would have to throw a charger on it on the 50 amp setting, then let the grid heaters fire, and then wait 10 minutes to let the batteries recover a little before cranking the starter without letting the grid heaters run again. Then it would fire and could stay running without dying. This was in 35 degree weather - nothing outrageously cold.

So, my point is, these grid heaters and starters will quickly expose even one weak battery. They really pull hard on these batteries during a cold start cycle, so dimming lights, etc. are nothing unusual. As long as the truck runs fine after it warms up and continues to start, I wouldn't be too worried about it.

AH64ID

Perfectly normal.. the grid heater draws 200 amps, the alt puts out 130 max...

It lasts for 2 minutes or until you hit 18mph.

All 3rd gen gauges are driven by the ECM.. The ECM is telling the dash gauge to read ~12.8 for the normal 2 minute cycle, even thou you don't have the heater..

bakdoor

OK, this maybe a dumb question, but is there some mechanism by which our two batteries are linked in series for 24v starts when needed? Someone over on the TDI forums suggested a dual battery set-up for diesel VWs, and someone mentioned that "my Cummins Dodge has two batteries," and then someone else suggested the 24v thing. I've never heard of this. Anyone else? I'm not sure I'm buying it...

AH64ID

They are not hooked up in series, they are in parallel to maintain 12v but double the CCA's.

coolbreeze

There are lots of trucks and heavy equipment that use 24volts, but not your pickup.

bakdoor

That's what I thought. When you can see the heavy-gauge wire going from one + terminal to the other + terminal with no switches or relays in between them, I don't see how they could be anything but parallel.

I'll have to go tell the peeps on TDI forum that they're full of ¢rap.

Thanks for the answers, y'all!