Im pretty new to diesels and this will be my 1st winter with one. Last year my transmission was down and then I shipped out to basic. Question 1:I have weak batteries (I need to replace them, but Christmas is making that tough) and I am wondering what all is going on when the "wait to start" light is on. I know the grid heater is one, but what else? What would happen if I just jumped in my truck and started it like a gas engine? The reason I as I am trying to save power for the starter when its cold.Question 2:When, and for how long should the block heater be plugged in before you start? What would I risk if I left the block heater plugged in all the time? High power bill, Fire? waste of time? As always, thank you!

WAIT TO START light comes on typically and runs the grid heaters that are draing 190A worth. So if the temps are above +32*F you can start without grid heaters with no issue. Below +32*F you might have issues getting it to start.So now if the block heater was plugged in about 2-3 hours before hand you wouldn't need to wait at all just hit the key and go. Block temperature should be roughly 90-110*F which will also be plenty for a no grid heater start.

.I think this answers part 1 http://forum.mopar1973man.com/threads/6753-What-Am-I-Waiting-For But basically yeah if you just put the key in and go, it will skip the grid heater since the grid heater needs time to run. Nothing else is doing anything special during the wait to start thing.. Question 2 is that you should probably plug it in for at least 4 hours for it to do anything. It uses 750 watts which could rack your power bill up quite a bit. My latest power bill says $0.106 per KWH so for each hour it is plugged in, it will cost you $0.079. If it's plugged in 4 hours a day all month, thats $9.55. If you simply leave it plugged in, a months worth 24/7 is $57. So it's up to you. Oh and as for when to use the block heater, I'd say any time under eh, 40F. It will start fine down to probably 20F but you might squeeze some more time out of the batteries if it's plugged in at 40F on down.

If you can even park the truck inside a enclosed building would be better than plugging in outside with the cold wind blow around the block.

would "cold wind" even be a factor, since that air is no colder than the actual temperatures? (i mean, wind chill has no bearing on inanimate objects?I plug mine in, and use a timer, so it only is "powered" for about 1.5-2hrs before I leave for work..

Thanks for the fast responce. I dont have any kind of shelter to park it under... I really wish I did..:(I dont drive my Cummins every day, It might get started once every few days or it might only get run once a month.. Just depends on how much extra fuel money I have:ashamed:

If it going to be parked for extended periods you might consider just pull the IOD fuse out using the clip.

OID fuse is the main fuse for the whole system? Good idea.

You might also consider throwing them on a charger to keep them topped off every once in a while. A weak battery sitting in the cold may go dead after sitting for a week or two. I have a battery tender I put on my Mustang battery and I put it in the basement for the winter. The battery is several years old and holding up great. If I were to leave it sit with no charger every winter for several months at a time chances are it wouldnt have lasted this long.

Absolutely, if you don't drive her regularly, use a float battery maintainer &/or pull the fuse mentioned. Otherwise those constant draws while small will evebtually kill the batteries & dead batteries may not recover. They can actually freeze! I have used a little dash solar panel with good luck for a while if the cord wouldn't reach.I've used a timer to run the block heater for a couple of hours... really helped with the cold starts. I managed to get through an extra winter before i had to replace the batteries.

Just a question and thought. First the question, do the block heaters have a built in thermostat of some sort to tell them to quit heating or do they just heat all the time?? Now the thought, I always try to plug mine in when i park it at night and the truck is at operating temperature. I just figure that if the heater is thermostatically controlled it would be cheaper to heat as it cooled than to heat from dead cold.

It would be nice, but no, they aren't. It's heating as long as it has AC power plugged into it.. This is why I use a timer to turn power on to my extension cord at a preset time... Mine is set to come on about 6am, as I generally leave the house around 700-730am. My timer is an inexpensive 15amp timer from True Value Hardware.. http://www.truevalue.com/product/15A1250W-Black-Outdoor-Heavy-Duty-Mechanical-Timer/3436.uts?refineByCategoryName=Lighting&keyword=timer

would "cold wind" even be a factor, since that air is no colder than the actual temperatures? (i mean, wind chill has no bearing on inanimate objects? I plug mine in, and use a timer, so it only is "powered" for about 1.5-2hrs before I leave for work..

if ambient temp is X the block will equalize to that temp. now lets say the temp suddenly dropped 50 more it would take X amount of time for the block to drop to ambient. wind would accelerate the drop in block temp to equalize to ambient. windchill affects everything, animate or inanimate.

if ambient temp is X the block will equalize to that temp. now lets say the temp suddenly dropped 50 more it would take X amount of time for the block to drop to ambient. wind would accelerate the drop in block temp to equalize to ambient. windchill affects everything, animate or inanimate.

agreed.

That why I will always suggest you at least try to get out of the blowing wind or park in a enclosed area. At leas then you heat is not wasted to extreme cold outside. Like both garages here are unheated so If the temp got down cold I would plug in the trucks while parked the shop. At least now the heat not wasted outside but heating a garage. 750W heater is still a heater regardless if it household appliance or a block heater.

I use a heavy duty timer also( for a/c's etc. Not "security" model). Not so cold, I set it for an hour or two. Cold to very cold 3-4 max. Sometimes in extremely cold weather the wait to start light may come on anyway. I've lifted the hood to check. The engine WAS heated. The sensor by the intake was cold enough to trigger the system. I dont wait under this condition, I just crank. Pre-heated will get you started and save cranking power. Good luck.