2001 Prius - dead battery with continuous horn

Hi everyone,

I hope this is the right forum for this. I've searched everywhere and haven't found the specifics of my problem so I feel there might still be hope. I live in New York City and rarely drive my 2001 Prius at all since I moved here 4 years ago. Before that I used to drive it a lot more, but it still only has 50,000 some miles on it.

I've been trying to take it on a good drive at least once a month. Sometimes I need to hook up a charger to the 12v or use a booster battery to get it going. This has worked up until now.

A couple weeks ago I started it with the booster and let it run until the engine shut off. I know this doesn't completely charge everything but I turned it off and it started again without the booster. So then a week ago I tried to start it again with the booster and got nothing except the hazard lights went on solid.

Since then I've been charging it with a Vector 2/6/10 amp charger on the 2 amp setting. After over 12 hours of charging it said it was charged, but if I disconnect the charger and connect it again after a while it still takes more of a charge.

Before I got the 12v supposedly "charged" and again after, at a certain point the horn would come on and stay on continuously. I either had to wait for it to drain the battery enough to shut off or disconnect the battery which I finally did. Now I'm charging the 12v by itself, when I connect it I still get nothing, no lights, nada, but if I hook up the charger while it's connected then the horn will still come on.

It would at least start two weeks ago. I highly doubt the traction battery has completely died in that time. The 12v battery was replaced less than three years ago so I could just need a new one but I'm hoping I can get at least one more start out of it so I don't have to get it towed. Any thoughts? Any advice much appreciated. (Also if anyone is really interested in acquiring a first gen Prius considering the above, please send me a PM).

 

Thanks, but I didn't see any first gen forums on this site. I started to post in the newbie forum (even less technical I figured) and it came up with similar threads involving 2001 Priuses, all in the Gen II forums. If a mod could move my thread to the appropriate forum that would be great.

 

No, it's the same one it came with. Before when I've brought it back to life the alarm system would come on with the horn intermittent, but something different seems to be going on here.

For the last couple weeks I haven't been able to get any lights to come on at all. No trunk light, no dome light, nothing. Just the horn. I managed to dig up a voltmeter and it read 14~ with the charger (the charger also has this function) and 12~ when I took the charger off. I also got a quick 10A reading along with a spark but I didn't want to risk blowing my meter. Seems like it's still got some juice in it and the capacity to hold some.

The booster and the charger are two devices I bought separately. I've never had them hooked up at the same time. I'll keep that in mind for the future about disconnecting the battery before charging it but it hasn't been a problem up until now. I assume the booster is just a smaller battery which you charge separately and the Prius just draws whatever it needs from it when you hook it up.

I could probably even take the subway, but with the battery appearing to at least hold a charge for a little while it makes me wonder if something else isn't going on. There may well be a problem with the ECU or another computer component that only a dealer would know anything about. Maybe there's just a fuse that needs replacing? Thanks for the help so far.

 

Thanks. I think this got me over the hump. I didn't really know where to start with the fuses and most of the big ones are opaque. Upon examination, three 15amp fuses are visibly blown. DOME and also AM2 and THRO. A visit to the auto parts store tomorrow during lunch should take care of this. The battery is now charging at a steady 2.2-2.3 amps so maybe it got past its false charged state and will be full by tomorrow.

Thanks again. I'll post a follow-up to help out the few others out there still driving around in first generation Priuses.

 

No, no polarity reversals but they may have blown either from the booster battery or from briefly having the charger on the 6 and 10 amp settings. Stupid, I know, but I just wanted to get it going and wasn't going to do it very long. I learned my lesson. Also I had gotten in the habit of boosting it with the key set to "on" so the alarm wouldn't go off. No more of that either.

So here's the latest:

The fuses did the trick and now it starts. But only for a few minutes, then it kind of sputters and shuts off. Trying to start it again kicks on the horn, windshield wipers and maybe an engine alert or two. I left the battery charger on overnight and it switched to automatic float charge, but I didn't want to leave it on during the day while I was gone so I disconnected it. Tried it after I got home and put in the fuses, it started but didn't last so I charged it some more and hooked up the booster.

It seems to do okay with the booster connected but I don't think the battery can hold a good charge or maybe it isn't charged sufficiently to where the alternator (or whatever it is on the Prius) can keep it charged. I'm guessing it may have been deep cycle discharged, which I've read conflicting things about whether or not that means it's toast. It was replaced I believe in late fall 2006 so it's still less than three years old. Right now the battery is back to drawing 2.5 amps or so from the charger and I can try that for a few more days. After a little more playing around I'll probably try and drive it to the dealer, maybe with the booster connected the whole way but taking local roads in case it completely dies on me en route. Surely even on the '01 Prius they thought of some way to automatically test the integrity of the 12v battery so it doesn't die in the middle of the road???

 

Throttle butterfly and induction cleaning procedures? Don't know anything about those but if you can point me to a good source I'm willing to give them a try. The tank is almost completely full, still has all ten bars on it.

The booster battery is a Black & Decker somethingorother, I don't have the specs in front of me. It's smaller than even the Prius battery. I think it says it can deliver a maximum of 200 amps. I'll have to look and see if it says anything about driving on it as the sole 12v battery (of course they probably don't address driving on it in combination with the HV battery). If I did drive it solely with the booster battery, I wouldn't want to do it for very long.

One thing I haven't had time to do yet is start it after the 12v battery has just been completely topped off by the charger. If it drains while it's not charging during the day then I'm guessing it either still has a long way to go to be fully charged or it has serious problems and needs to be replaced. Hopefully I will have time by this weekend to try this but a rain forecast in the next few days is going to complicate things, although I might be able to cover it with a tarp. In the meantime I'm just going to keep charging it whenever I can, assuming the charger is smart enough not to damage it by overcharging at 2 amps.

 

So I'm going to give this maybe one more try before I break down and take it to a dealer. Again, sorry this is in the wrong forum. I swear I didn't see the Generation 1 forum before (maybe the link was different?)

I went ahead and ordered then installed the Miata battery from eLearnAid and it seems fine. It was testing at 12.6v out of the box so I didn't charge it any more initially. I installed it Wednesday, it started fine and seemed to stay running so I shut it off. Saturday I took it out on an errand for about an hour. No problems during the trip except what I had been neglecting to realize was a bigger problem this whole time: since I replaced the fuses, the interior lights work and everything comes on when I turn the key to ON, but in ACC mode none of the accessories or anything come on. I did notice a whirring sound of some sort when I hold it in ACC mode, then when I turn to on the engine starts along with a brief beep from the horn and the windshield wipers wipe once. This behavior has been consistent with both the old and new battery since I replaced the fuses.

To top it off, when I got back from the errand I left it running for a while and the engine stayed on longer than I thought it should while I was trying to call Car Talk (didn't realize they call you back first and don't take live calls). It seemed to sputter and die during this time and when I tested the voltage it was only about 11.5. I broke out the charger and charged it overnight and got it up to 13.5, and then I got a ! triangle after starting it but still nothing when the key is on ACC. The battery charger does have an alternator check which I tried and it came back bad, but it does say your specific model of car may have crazy electronics which are not compatible with the alternator check.

So it appears the 12v battery is not being charged, and I can only assume this is related to ACC not coming on. I've tested the ACC fuse along with most of the others and they all have low resistance, and all of the non-opaque ones visually look good.

note: I know this is already long-winded, but for anyone who cares about the surrounding details: if possible I need to take this car on a 1,000+ mile trip in late November to be inspected in another state. I'm hoping against hope that since I'll have to take it to a dealer then anyway, I can just wait until then to have any major issues looked at in one shot. Bad idea?

 

Thanks everyone for your help, but I made an appointment to take it to the dealer tomorrow morning. Since I know I can at least drive it that far I think I'm just going to do it. I tested the voltage with the engine running and it drops down to about 11.5v so I don't think there's any way it's charging. I tried to take the 110A DC/DC fuse out to test it and ended up popping the clear plastic cover off. At least I saved a few bucks and hopefully got a better battery with the Miata battery. If they try and charge me an arm and a leg for something that's simple and possible to do myself, maybe I'll give it another go. I'll let you know how it goes.