...okay so you'd tend to think alternator, but why would I draw more current at startup than any other time, especially if I have a brand new beast Interstate battery in there? ...again it's fine in general, but there are major signs of excess current draw / limited supply when I start.

For one, I can hear the alternator whine when I start it in the cold (I'm talking 10-20 degrees F so, fairly cold..) - one day the brightness on the LCD screen actually changes as I increased RPM while I waited for engine to warm up! This was with the heated windshield, heated seats, and the air compressor running - all of which are fairly high current devices - but still, this thing has a MASSIVE battery in it, and I wouldn't expect that to be transferred into the alternator directly - the batt. should take a big chunk of that (like a mini capacitor).

Yet still, as I increased revs off idle to ~1200, the LCD brightness increased (kinda bizarre considering the electronics, transformers, and circuit boards that control the screen...) and interior lights, air compressor revs, etc increased.

I guess if your alternator is putting out ~30% less current it might be okay during highway driving (or warm temps, or once batter is charged) but NOT okay if battery is COLD, and you're drawing a lot of current?

Maybe I'm thinking out loud here. Does anyone else notice a lack of current supply at low/normal idle after startup when COLD cold?

 

Isn't it normal to draw more current at startup than any other time? I always thought so...as for your noted cold-weather effects; yep. I've always thought that was kind of normal when it's THAT cold out.

 

If you are dealing with temperatures below 41 degrees F, the LR3 adopts a electrical load management program on start up. It reduces power to your various systems based on load and battery voltage. And with temps that low your battery is going to be very low, it doesn't mean your battery is bad. First it reduces power to your air suspension and prevents operation of the compressor, then reduces power your seat heaters then reduces power to your entertainment system, which explains your screen brightness. Your maximum volume Should be reduced as well. If its still unable to maintain a good voltage it will actually shut your seat heaters off, so the fact your heaters are still on means the LR3 hasn't gotten to that point. So it sounds like everything is operating normally. How long this load management lasts depends on ambient and coolant temp, but is between 5-15 minutes

 

I've been around these things for many years and never heard this system referenced before, but just found it in the workshop manuals.

ATCM - Automatic Temperature Control Module. Apparently responsible for everything from cold current management to the (more obvious) raised idle to increase AC compressor efficiency among other things.

Sure enough, I found everything from temperature tables dictating "warm up" times with varying ambient and coolant temps, to load tables and priorities for all high current devices.

I'm glad I wasn't losing my mind! It definitely seemed to be impacting the higher-load items in the vehicle.

That's very very impressive on a 10 year old vehicle - there's some type of dynamic load bus which is capable of distributing power to/from circuits based on a calculated amount of headroom supplied by the alternator.

Crazy crazy stuff..

 

Wow. Very cool. I certainly learned something new about the car. As far as your problem goes... that definitely makes it sounds like an alternator issue.

 

Well I had a look at the table, and everything I noticed being impacted was included in the cold start priority table - everything acts normally after the cold start warmup times elapse in the other table as well, so it's actually probably working fine.

It also sounds like regardless of generator / batt performance it'll be far more likely to throttle certain loads till the specified time and temperature requirements are met.

 

Ah, I just took this statement, "The ATCM calculates the electrical load from the battery voltage and generator output voltage, and compares the result against the maximum load available from the generator." to mean that perhaps your maximum load available from the generator wasn't high enough. If the max load available is low, I can see the system "managing" the electrical devices more often.

I don't THINK I've ever seen my LR3 managing the electronic devices, but now that I know about it, I'm going to have to look for signs. :P

 

I only remembered the LR3 had this system, because I am a marine mechanic, and its actually pretty common on newer ships that have multiple generators to shed load if a generator goes down, so it stuck in my mind as an interesting feature

 

Airplanes do that too...load shedding.

 

I think both of your points are all the more reason why I'm so impressed that a decade-old consumer vehicle is equipped with this sort of feature. Especially considering the unusually large battery and alternator lol. Definitely ahead of its time, but that tends to be land rovers deal. Kinda like the DII being the first with brake force distribution and traction control.. woah.