Since it has begin to become cold, I have notice that my voltage is bouncing from 12.8 to 15.2 volts at idle. Does not seem to matter if the engine is cold or not. The RPM is staying steady. However when driving the charge tends to settle out around 14v unless at idle speed. The heater fan and all accesory's relfect the charging variation by going lighter or faster slower etc.

Any ideas?

 

100% normal, I think it is even in the trucks manual, cold days the grid heaters cycle off and onn, when they are on you see dropped voltage at the gauge..... they will cycle for a bit or untill you drive about 5 mph and then they stop.

 

Thanks for the quick response.

 

Even if the grid heaters aren't cycling, the A/C runs in Defrost mode, and it seems to suck a little when it's cycling.


phox

 

But in that case, the alternator should be able to compensate for the increase in electrical load so you wouldn't see it on your batter voltage gauge.

The alternator can't supply the batteries and grid heaters at the same time, so you see a dip in voltage (and dim lights, slower wipers, etc.)

 

Who designs these electical systems? They should be shot. For cryin' out loud, it isn't hard to make it so everything doesn't fluctuate like that if they would just get creative. How dang simple is it to design things for 12 VDC and keep them constant?

 

like the others where saying this is normal. what you are seeing is the intake heater cycling. Your CTD will do this if outside temp. is about 35 or below. this is also why your wait to start light stayes on for a bit longer. after your CTD is running the intake heater will cycle for about 3 minutes and you will see the everything electrical will be about half power. if you hold your foot on the go peddle for the first 2 minutes your volts will stay low. If you drive over 15 mph or so while this is cycling the ECM will shut it down so not to get damaged

 

I have replaced the stock carter lift pump on my 01 CTD with a holley unit. I put the holly back by the tank, ran 3/8 hose throught, and installed a fuel pressure guage. I have noticed when the intake heater is cycling it cut power to everything electrical. so the lift pump takes a wip'en trying to pump all the fuel the vp-44 needs at half power. It is very noticeable on the pressure guage. I think thats whats kill the stock pump?

 

Who has a 200+ amp alternator?

I'm just a mech. engineer so don't jump all over me, but each grid heater pulls over 100 amps. When you have both going at the same time, your alternator would have to supply 200+ amps to keep the system at 12v, right?

Tell us how you'd do it.

 

I knew this question was coming. First off, isolate the batteries so run-critical things are on one and non-critical things are on the other. Put all the lights/instrumentation and junk on one. Put grid heaters and engine electonics on the other. Let the alternator charge both but don't let one draw from the other. If you leave your lights on and drain the non-run-critical battery, guess what, you can start your engine, drive off, and the rest will re-charge itself. How hard was that? No really, I'm sure there are a lot of things that I don't realize and I sure as heck wouldn't want to design the whole system. But crap, think of things that really make a truck worth buying. Drop the fancy junk like mpg readouts, heated mirrors, and bs that is just a bell or whistle and make a truck start everytime and never quit. How 'bout a fuel pump that works? An isolated battery setup would allow the engine components and junk to draw all they want and would let the dash junk, wipers, lights, cd player, and misc keep a constant voltage.

Does that make any sense? I'll check back tomorrow for replies.

JWB

 

Just adds more cost to the vehicle. I'm not defending them but it is really a big deal for the amount of time the grid heaters are on for? I'd rather see improvements in more reliability based areas. Even in many homes when a heavy electrical load kicks on (i.e. - ac condensor), you can get a voltage drop sometimes. Yes, its fixable with capacitors, increased wire sizes, etc. but usually not cost effective unless the situation if severe enough to cause damage. Comes down to $$$$$$ as usual.

Sticky

 

yes I think you are right about bigger size wires.. Thats why california always has brown outs..... somebody is using the ac outlet to power their cold cummins... makes the whole darn state go brown!!!! or maybe thats just the people coming up from the border!

 

EXACTLY! They cheapen them up to the point of them barely working properly. I totally agree with that. I'm sure this is a tangent to the original question, so I'll get off of here. Remember, just enough to get by, that how they make 'em. Plastic, plastic, and more plastic. And let's sell 'em with 20 inch rims so tires cost $300 each! That is real intelligent.

 

Would you like to trust starting your diesel with one battery? How long do you think the battery hooked to the grid heaters would last with that kind of cycling. It's not like starting where the draw is just for a few seconds. The two batteries in parallel is a good system in it is splitting the draw over the two starting type batteries. These aren't designed to be drawn down much but to be able to give a large amount of current for a short time. You could go and split the system like you suggest but then you may need 4 batteries, two sets of parallel or two GIANT batteries. Even with the isolated system, you will see the lights dim because the voltage will drop whenever the alternator can't supply enough power and the batteries have to. The alternator is supplying about 13.5-14.5 volt and the batteries will give about 12.5-12.8 when fully charged. This drop in voltage is what you see in the light bulbs.

 

I know this. You could drop the isolation during cranking. Whatever....just make it better....that's all I'm saying. It couldn't be too hard.