Been having issues with my 2008 TL Type-S since the alternator failed this summer.

Had the original alternator die this summer and it killed the battery when it went. Battery light came on and I just made it home. Battery would no longer take a charge and alternator was smoking when I opened the hood. Ordered a Denso reman from Rockauto and got a new Diehard AGM battery under warranty.

Everything was fine for about 2 months and then one day the car didnt want to start. I jumped the car and it was fine for a few days until it, again, it wouldn't start. Battery voltage was low (~10V), and the battery wouldn't take a full charge. Just stayed at around 10V. I went out to and got a brand new Odyssey AGM battery. Battery lasted 1 day and car died while leaving work. Pulling out, it just shut off. Tried to jump, it would run for about 20 seconds and die again. No battery light came on this time, no warning at all. Just died. I went home and got a spare battery I have for the boat and managed to drive the car home. Odyssey battery was toast. 2.2V and wouldn't take any charge.

Ran through alternator tests based on a ChrisFix YouTube video and everything checked out perfect. Didn't know where else to look for issues. Ended up replacing alternator again (under warranty) and got a new battery at Costco.

Everything was fine for a month or so, until a few days ago. Noticed car starting a little slower, but still started. Thought maybe it was due to the very cold weather here. Nope, car sat in the garage a few days and battery is at 5.5V. Put it on a charger and it maxed out at 12.8V. Put the battery load tester on it and it dropped to around 11V.

When I tested for a parasitic draw, I believe it was at .04mA. Red lead on the negative post and black lead on disconnected ground wire. Could be wrong, but that's what I saw on a video.

Really have no clue where to go from here. It seems like each time it starts slow a few times and then within a few days the battery is too low to start the car and will not take a charge. Obviously I'm going to have to get yet another battery and start testing from there. I do have a new Autel 808 scan tool, a digital multimeter, and a battery tester. Any guidance is greatly appreciated before I throw in the towel. Also, very new to using a bi-directional scan tool.

 

have you unplugged the HFL unit?

 

I'm almost positive the previous owner did, going to 100% verify tonight after work. Couldn't find my trim removal tools last night.

 

This would've shown up when he did the parasitic draw test.


Your procedure is correct, I just question the scale of your units. Anything less than .040amps (40mA ) is fine.
Now do you truly have .00004 amps? B/c that would be impressive if your DMM read that low.

If it is indeed .04 amps with your HFL unplugged.... this indeed is going to be a head-scratcher

 

We're going to go with me being wrong, I figured the HFL would show up if it was drawing power. I'm going to double check anyways. Here's a pic of what the DMM read when hunting for a parasitic draw.

 

Yea those readings look fine. Now how LONG were you taking that reading for? Did you immediately disconnect the leads once you read .04amps?
(If HFL is disconnected) I would leave the leads connected for a parasitic draw for as long as you have to watch the DMM like a hawk. (10-30 minutes??) Maybe some circuit is "waking" back up eventually, bumping that amperage.


*edit* in the meantime you can get this cig lighter voltmeter, I keep mine connected at all times, even when I was having a parasitic draw, to give me a heads-up if the battery is a bit low

 

I think I have that same voltmeter for my boat actually. I have been using mainly the Hondata app or sometimes the Autel to monitor voltage.

I saw your post in another thread. That reading was only after like 2min maybe. After work today I'll watch it for an extended period. You leave the ground cable hooked up while taking the reading?

So the DMM red lead to negative battery post and black lead to the battery ground cable while it's still secured to the battery? At what point do I disconnect battery ground cable and check it like in the picture I posted?

Ran out of time last night before temperature dropped to check HFL. I'll check today after work to verify and report back.

Took car for a spin last night with new battery. Everything seemed perfectly normal. No voltage readings that were too high or too low. I'll post a pic of what I had up on the Autel, but honestly I'm not sure if I'm looking for the right things.

 

Leave it disconnected from the battery the entire time, just like your picture. You can use a c-clamp to hold the red lead to the post.

 

Confirmed HFL is disconnected. Couldn't watch it the whole time, but DMM had it at .04 when I was watching it. Was disconnected for probably 45min.

I drove to drop it off at a shop for an alignment tomorrow and the Hondata app had it reading 14.2V-14.4V the whole way there. No clue, I suppose we'll see if it happens again and just continue to monitor battery voltage every drive. I don't see what else to look for at this point.

 

I’m currently dealing with a similar issue, battery died without warning, after being parked for ten minutes while I ran into the store. I got in and it was completely dead when I attempted to start it. Got a jump and went right to auto store for a new battery. I tested the alternator and it read fine. Almost a month to the day, battery light came on, I was too far from home to try to drive it back, so parked in safe spot, turned it off and it was dead as a door nail. Took the battery out and took it home to put a charger on it overnight, but it wouldn’t take a charge. I returned the battery, installed and car started right up, no battery light. I attempted to get it home with the fresh battery and try to figure out if the alternator went in the past month since tested. I didn’t make it far, battery light came on and tranny slipped when I got on the road, so I got it parked safely again. I’m sure I will have to replace the alternator once I get it towed home, but I’m amazed at how quickly it went from OK to completely dead battery. I’m wondering if there’s something drawing on the battery in addition to alternator being shot.