With the car running, my voltmeter shows that my 12v battery is draining about .1 volt every 2 seconds. I'm able to drive the car for 3-4 minutes (before dash blinking starts and car dies). From reading the forums, it sounds like my inverter or dc/dc converter has gone bad or I've blown the 100A fuse or perhaps the inverter pump has gone bad. So, I'm trying to test the fuse (see pic 1), hoping for the best. I've read that I need to lift out the fuse box to test that fuse (true?) I found the two fusebox mounting bolts (see pic 2 and 3) and was able to remove them. I disengaged the clip (see pic 4). However, as yet, I'm unable to lift out the fusebox. There is a cable (assuming wiring to fuses and relays) preventing lifting (see pic 5). Before I get too much pulled out, I thought I'd ask if I'm proceeding correctly. Is there a better/easier way to test the fuse or dc/dc inverter? I don't currently have an OBD II but I've ordered one. Help, please.
Possibly, but it's new (1 month). I've drained it down to 10 a few times. Charges up to 13+ volts with external charger. With engine on (in Ready mode), I use a voltmeter to test across the battery. I'm expecting to see something similar (13+ volts) but I see the voltage steadily going down, as noted in the post. So, I'm thinking the 12v battery is not being charged.
Update: To test whether the inverter is charging the HV battery, I connected an OBD II plug. I can see that the HV battery is charging (and discharging) when the engine is running. The pack voltage increased substantially (290 to 310) so I'm fairly confident that the inverter is working. Still troubling is why the 12v battery is not being charged. My understanding is that the dc/dc converter steps down the HV to 13.8. How can I test the main (100A) fuse?
Suggestion: It sounds as if you have already used a meter at the battery terminals, and your reading stays below 13 even after you make the car ready, and does not rise to 13.8 as it would if converter output were reaching the battery. I would suggest also taking your meter and testing various other circuits in the car. Do you see any of them rise to 13.8 when the car is READY? (One easy place you could test that is the fuse box; the ATM fuses all have test points exposed on the top.) If there is no 13.8 anywhere, the DC/DC converter itself may be offline. If you have 13.8 on some circuits but not others, the converter is producing output but that output is not getting everywhere. The 100 amp DC/DC fuse in Gen 1 is not (schematically) right at the converter; there are branches taken both up- and downstream of it. If that fuse were open, for example, you would see converter voltage (13.8ish) at places like the CDS FAN fuse, or ABS NO. 4, but see battery voltage (12ish) on circuits like ABS NO. 3, AM2, or DOME. You can check all that with a meter, and no skin off your knuckles. If you get some other picture that isn't that exactly, you may also be able to figure that out looking at the wiring diagram (more info); the pages can be turned without loosening any bolts, persuading any clips, or fighting with any cables.
Great suggestion, ChapmanF. I had (wrongly) assumed that the dc/dc converter would charge the 12v battery and the 12v battery would power the various 12 circuits. I appreciate your specific information (CDS fan fuse should be 13.8ish); that is just what I needed. Thanks for providing the link to help find the wiring diagram - a wiring diagram will help me figure out other things in the future. Great post!
Update: 1. The car does not start with my OBD II plugged in! I pulled out the OBD II and started the car. The OBD II reported p1636 but after clearing, it didn't return. I imagine (I need to test) that if I try to start the car with the OBD II inserted, p1636 will return. 2. The voltage at the CDS FAN fuse is 13.93. So, I'm thinking that I can reasonably assume that the inverter and converter are working. 3. The voltage at the DOME fuse is 11.45. By visual inspection, the main 100A fuse looks intact. However, considering ChapmanF's comment, "If that fuse were open, for example, you would see converter voltage (13.8ish) at places like the CDS FAN fuse, or ABS NO. 4, but see battery voltage (12ish) on circuits like ABS NO. 3, AM2, or DOME." If I interpret this correctly, I need to replace the 100A fuse. Now, the question is, "How do I get to the bolts/nuts to replace the fuse?" Does some part of the fuse box lift out? Do I need to lift out the entire fuse box?
Update: Upon closer inspection, with some adequate lighting, the main 100A fuse appears to be open (see pic). I think I found the relevant page in the electrical wiring manual (see below). The green annotation show the connectivity from the converter to the CDS FAN fuse. The red annotation shows connectivity from the battery to the DOME fuse. If the main 100A fuse is intact, the red would be at the same voltage (~13.8) as the green since there is connectivity and ~13.8v comes from the converter. However, if the main 100A fuse is open, there is no connectivity so the DOME fuse would be at the battery voltage (decreasing from 12.5 over time).
Looks like you've found the answer all right. I think there are at least one or two threads around where somebody got that fusebox loose enough to get that fuse out. It didn't sound like a walk in the park.
Yes, thanks to you, ChapmanF. I figured out how to get that assembly apart and the fuse out but, you're right, it was a task. I couldn't find a relevant thread for Gen 1. If you happen to have a link, please post it here. Perhaps I can document the procedure when re-assembling. Now, I have to go find a new fuse.
Here are at least a couple of those threads: 100 Amp Fuse Replacement | PriusChat Reversed jumper cables blew 100A fuse in engine compartment | PriusChat Some very useful pics in the latter, but nothing overly systematic in terms of how-to. Do you know why the fuse blew? Unfortunately, it's usually because there's a root problem somewhere, so if you don't know what did it and don't fix that problem then it will likely just blow again.
The history isn't covered in this thread, but often stories involving that particular fuse have a backwards jump start as a flashback, which is nearly always followed by an "I am not going to do that again!" and is therefore self-correcting. If that's not the story, then yes, there may be some lingering mystery.
Perhaps a senior member or the forum master can help. There are main forums for 4th Gen Prius, 3rd Gen Prius and 2nd Gen Prius. The 1st Gen Prius is kind of a sub-forum under 2nd Gen Prius. This is a bit confusing and Gen 1 things that I search for return unwanted Gen 2 items. Can we create a main Gen 1 forum? Then, we can migrate Gen 1 items out of the Gen 2 forum into the new Gen 1 forum.
There are old posts from me complaining about the same thing, but I think it was eventually explained to me; there are a lot of links to existing threads/posts around, and that's valuable because it helps knowledge not be lost under the sands of time, and I don't think the admins had a good way to migrate the content without leaving those links broken. If so, I take that as a good enough reason not to disturb it, even as much as I share the idea that a top level forum (if starting from scratch) would be nicer.
This has been asked for several times. Here's the most recent example : Feature Request: Prius Gen 1 / Prius Classic Subforums
