Is it possible the key fob just needs replacement and is causing the intermittent sleep failure?
I fixed a parasitic drain on my car in 408 days
11–20 of 515 posts
Re: I fixed a parasitic drain on my car in 408 days
#12Well this is timely. I have a parasitic draw on my NC Miata. The first mechanic just replaced the battery. The second told me it's normal for the battery to die if you don't drive it for 3 days (because "cars have computers now"). It seems like mechanics really don't like digging into the electrical part of the car... but these days that encompasses more and more of what can go wrong. Without time to dig into it myse…
> it's normal for the battery to die if you don't drive it for 3 days I've heard this nonsense a couple times now. I was incredulous at first but everyone seems to say this. What are anyone's suggestions for a weekend-only car? (I bike to work so I don't need a car on weekdays.) Trickle charge the car battery on weekdays?
Or disconnect the battery (you’ll have to reset the clock, etc., which is annoying).
Re: I fixed a parasitic drain on my car in 408 days
#13Well this is timely. I have a parasitic draw on my NC Miata. The first mechanic just replaced the battery. The second told me it's normal for the battery to die if you don't drive it for 3 days (because "cars have computers now"). It seems like mechanics really don't like digging into the electrical part of the car... but these days that encompasses more and more of what can go wrong. Without time to dig into it myse…
> it's normal for the battery to die if you don't drive it for 3 days I've heard this nonsense a couple times now. I was incredulous at first but everyone seems to say this. What are anyone's suggestions for a weekend-only car? (I bike to work so I don't need a car on weekdays.) Trickle charge the car battery on weekdays?
It's nonsense! If a car is dying after not being driven for several months, ok fair enough. If after several days a particular year make model dies it deserves a recall!
Re: I fixed a parasitic drain on my car in 408 days
#14Well this is timely. I have a parasitic draw on my NC Miata. The first mechanic just replaced the battery. The second told me it's normal for the battery to die if you don't drive it for 3 days (because "cars have computers now"). It seems like mechanics really don't like digging into the electrical part of the car... but these days that encompasses more and more of what can go wrong. Without time to dig into it myse…
It's fairly straightforward if the car is unmodified, as everything should be fused. Multi-meter between positive terminal and positive lead and pulling each fuse to see when the drop goes away will isolate the circuit. Then you've narrowed it down pretty far and can go from there. The horrible thing is if the car is modified, and you discover an un-fused circuit.
I’ve had unknown draws before and many times they’re not constant draws. A constant draw is easy and quick to find. A draw that only happens when some module or other wakes up is a lot harder to find.
Re: I fixed a parasitic drain on my car in 408 days
#15Earlier quoted context omitted.
I thought about this but the problem with newer cars (mine at least) is killing the power wipes the memory so it won't pass an emissions check (or something like that). After my battery died I had to find an excuse to drive an extra 100 miles so I could pass emissions. On my car the emissions laws definitely caused more emissions than they saved that day.
I hear this all the time, but I have never understood it. If I clear my drive cycle monitors, they are all passing again just a few miles later. Do some vehicle manufacturers just put insane constraints on the drive cycle monitors?
That seems reasonable since anyone could clear and tune an engine with minimum effort to pass emissions without a history requirement.
Re: I fixed a parasitic drain on my car in 408 days
#16Had the same problem recently with a 2011 Mercedes. Didn’t figure it out until eventually the Keyless Go module (which allows push to start and automatic door unlocking) died. This fixed the parasitic drain.
Apparently when these sorts of modules are dying they fail to turn off and drain the battery by constantly searching for the key fobs. Incidentally while the battery drain was going on the key fob batteries were dying extremely quickly as well, also suggesting a lot more communication than normal was occurring.
Re: I fixed a parasitic drain on my car in 408 days
#17Earlier quoted context omitted.
I thought about this but the problem with newer cars (mine at least) is killing the power wipes the memory so it won't pass an emissions check (or something like that). After my battery died I had to find an excuse to drive an extra 100 miles so I could pass emissions. On my car the emissions laws definitely caused more emissions than they saved that day.
I hear this all the time, but I have never understood it. If I clear my drive cycle monitors, they are all passing again just a few miles later. Do some vehicle manufacturers just put insane constraints on the drive cycle monitors?
There is a drive cycle set of requirements and it’s usually possible to clear them in under 20 miles. Trying to figure which part of the cycle isn’t accomplished yet is the challenge. I’ve chased it down on my wife’s Honda when we were trying to get it to go “Ready” the same afternoon. Usually just not doing anything unusual for a day or so of normal use is enough, but you can often query the OBD2 system to get the portion of the cycle that’s not yet complete. Just doing a long highway drive isn’t going to do more than a moderate highway drive already did.
Re: I fixed a parasitic drain on my car in 408 days
#18Earlier quoted context omitted.
I thought about this but the problem with newer cars (mine at least) is killing the power wipes the memory so it won't pass an emissions check (or something like that). After my battery died I had to find an excuse to drive an extra 100 miles so I could pass emissions. On my car the emissions laws definitely caused more emissions than they saved that day.
I hear this all the time, but I have never understood it. If I clear my drive cycle monitors, they are all passing again just a few miles later. Do some vehicle manufacturers just put insane constraints on the drive cycle monitors?
> Do some vehicle manufacturers just put insane constraints on the drive cycle monitors?
Yes. Combine with the fact some only pass after certain conditions (eg. over 3000 revs for 10 mins, or idle for 5 mins, or only after 3 starts, only when the outdoor temperature is within this range, etc). Sometimes those conditions aren't stated in the manuals.
That makes the checks passing seem more like a random process and driving more will usually make them pass, eventually.
And drivers without a code reader won't know when it has passed, so they are usually instructed by mechanics to drive a long way to be sure before taking it in for a test (don't want to have to reschedule the test just because you didn't drive it enough).
Re: I fixed a parasitic drain on my car in 408 days
#19Well this is timely. I have a parasitic draw on my NC Miata. The first mechanic just replaced the battery. The second told me it's normal for the battery to die if you don't drive it for 3 days (because "cars have computers now"). It seems like mechanics really don't like digging into the electrical part of the car... but these days that encompasses more and more of what can go wrong. Without time to dig into it myse…
> it's normal for the battery to die if you don't drive it for 3 days I've heard this nonsense a couple times now. I was incredulous at first but everyone seems to say this. What are anyone's suggestions for a weekend-only car? (I bike to work so I don't need a car on weekdays.) Trickle charge the car battery on weekdays?
No car I've owned in the last decade has actually drained in a few days. Any car that does has a problem.
Re: I fixed a parasitic drain on my car in 408 days
#20Well this is timely. I have a parasitic draw on my NC Miata. The first mechanic just replaced the battery. The second told me it's normal for the battery to die if you don't drive it for 3 days (because "cars have computers now"). It seems like mechanics really don't like digging into the electrical part of the car... but these days that encompasses more and more of what can go wrong. Without time to dig into it myse…
> it's normal for the battery to die if you don't drive it for 3 days I've heard this nonsense a couple times now. I was incredulous at first but everyone seems to say this. What are anyone's suggestions for a weekend-only car? (I bike to work so I don't need a car on weekdays.) Trickle charge the car battery on weekdays?
Yes, they make battery tenders that are specifically for this. They'll trickle charge when needed, but also not charge at all when the battery is at the right voltage.