Hey folks,

I tried bumping an old thread with a similar issue from September but am now trying to stick to forum etiquette and starting a new thread.
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I have a 2005 TL, Base with Navi, 135,XXX miles. I've put 30,000 of those miles on the car in the last year and a half since I bought it. It has been an extremely reliable car up to this point.

After sitting for about 36 hours, the battery was drained almost flat. Before I parked the car, I had just finished a 120 mile drive and all systems were working correctly. I used a boost box to start it and then let it run for about 20 minutes then took it on a short drive. Before I shut it off, everything electrical seemed to still be working correctly. No slow turn signals, no dimming lights. I shut the car off, manually turned on the dome light and restarted the car, the dome light didn't even flutter and was still nice and bright. The next morning the battery was dead again. No, I did not leave the dome light on overnight.

Made my way down to the local NAPA and picked up a new battery. Checked cables on the old battery and they were nice and tight. They were also free from any corrosion. Dropped the new battery in and all systems were go, car started immediately on the first twist of the key. Reset the navi and the radio and all was good. The car started immediately this morning and showed no problems on my 40 minute drive to work. All lights were functioning and were nice and bright when I arrived at work.

Went out at noon to run an errand and it would not start. Power to all systems but when the key is twisted to start nothing happens... just silence.

My first round of thoughts are that the battery (replaced yesterday) and alternator are fine (I actually doubt the old battery is dead now and just flat, needing a good charge). Nothing of the driving behavior indicated a bad alternator or really a bad battery. Especially since everything still powers up just fine except for the starter.

My second round of thoughts, on what else immediately jumps to mind after battery and alternator are ruled out, jump to starter relay, starter/solenoid, ignition switch. Does this sound correct to you folks?

I'll have to leave the car overnight and I'll bring my meter back with me in the morning. Hopefully I have given enough background information and basic troubleshooting to cover most basic responses. If not, just let me know. From several other threads, the starter jumps out as the #1 culprit but would a bad starter actually drain a battery? I have not experienced that sort of failure before with other vehicles... not to say that it couldn't happen though.

Help and suggestions much appreciated...

In the bump, thoiboi responded and indicated that the HFL can cause a drain.
My HFL has not worked for nine months (I am planning on replacing it though) and the battery drain that preceded the no start and battery replacement was sudden. I have not seen a slow drain issue in the last nine months, even when the car has sat for up to a week without running. So while I understand that an HFL can cause a drain, it doesn't seem related to this issue of no starting with a brand new battery holding its charge. I did and do thank thoiboi for the information though.

 

Have you disconnected the HFL to rule it out? A malfunctioning HFL is a know problem many have and will kill a new battery over night. I would unplug it, considering you are describing exactly what happens when the HFL fails.

 

^ This. My HFL stopped working. No battery issues for about 6 months. Suddenly if the car sat longer than 8 hours, dead battery every time. Researched it, discovered the issue with the HFL, disconnected HFL and the problem was immediately resolved.

 

Check battery volts @ 12+ volts, turn on lights, interior or exterior, try to start, if lights stay bright, starter or starter circuit, not the battery.

Last month, while in Florida, pulled into a convenience store and a couple of fellows were trying to jump a Charger. When I came out, thought I'd take a look and as they stated the jumper cables weren't working, thought I'd throw the battery pack on the in trunk battery, no go. I checked battery voltage with the mm, 12.5. Had them turn on the lights, hit the starter, lights stayed bright, bad starter.

Another incident about a week later, a car wouldn't start at another store. Put the battery pack on no go, good voltage, but no power at all. Checked the battery cables, positive was loose. Tightened it up and was good to go. The son had just worked on the sound system and I guess he forgot to tighten the clamp after the job was done.

Just make certain cables are clean, tight, and voltage correct.

 

Same thing happened to me with my HFL. I unplugged it and voila, working car again. I have since replaced the HFL unit, no issues since. I have also replaced my battery but found that the positive cable connector wouldn't clamp tight on the terminal so I replaced that too.

 

Thank you for the warning and I'll be sure to unplug the HFL for now until I can replace the module. However, I'm not sure that I am describing exactly what happens when the HFL fails unless the HFL failing can affect the starter, solenoid, ignition relay or ignition switch. See below...

UPDATE: When I got back to work this morning my TL still had plenty of charge in the battery after sitting overnight (overnight low was in the low 20's as well). Put a meter on the battery and it is registering 12.5 volts, it has now been sitting in the same location, and not started, for more than 24 hours. Turn on the ignition and everything still reacts as normal until I twist the key to the start position, then nothing happens. Lights do not dim and the voltage on the battery did not change when the ignition switch was twisted to the start position. So it would seem that power is not even being diverted to the starter at the moment.

Since the new battery did not drain overnight, I think we can rule out the HFL for the time being (I'll still unplug it as a precaution) as the battery does not seem to be the root problem. I have not experienced a failed starter draining a battery overnight, but I suppose it could happen. A relay that hung open could cause a rapid drain and if it has failed, now closed it would no longer draw power. Same with the ignition switch if it has a fault.

The next diagnosis steps I suppose would be to verify whether or not 12 volts is actually reaching the starter, if it is not then look into the relay and then the ignition switch. At least that seems to be the most logical progression to me.

I'll need to get it towed home or to a local shop though. We have a major storm coming in this afternoon and I won't be able to work on it in the parking lot today. Wish me luck and I'll keep everyone informed as to what I find out.

 

Following up:

It was the starter. Relay and ignition switch were fine. Replaced the original starter with a Bosch unit. More money but a better service record.