12 volt battery positive terminal connectors question

Traveled out of town to pick up some Prius parts from a car breaker 3 hours away and happened upon a nice looking 2005 with a For Sale sign along the way. My partner and I stopped in to take a look on our way home, but weren't really prepared. I did have my bi-directional scanner and Dr. Prius with us, and a 10mm socket & wrench, but no other test gear.

Owner stated car had approximately 380,000 miles on the original engine, and that he was the second owner (purchased with 240,000 miles on it). This past late January a Red Triangle of Death sent him to a dealer, who in turn relieved him of $3,800 for a new Toyota OEM hybrid and 12 volt battery replacement and sent him on his way. Car ran fine for a while (his dash cluster still functions, but the odometer stopped at 299,999 rather than just blanking out, as I've also seen), until a few weeks ago when he got a red brake light, ABS, VSC, Check Engine amber, and his ABS alarm started buzzing. Dealer diagnosed bad ABS accumulator/pump and quoted something insane, so he took it home to re-evaluate and regroup. Hence the For Sale sign...

The car started fine, and hybrid was initially low from sitting, but I had called the number on his sign on the way down and told him wed be stopping by on the return to look at it, so he started the car up and immediately started up the car and began running the A/C when I called back with an ETA about 15 minutes out. A/C was blowing cold, the hybrid battery screen was showing nothing, and the warning lights were all lit, so I shut everything down and went to look at the battery conditions. Looking down upon the positive battery terminal there are two quick connectors that plug into what I think is a circuit breaker that's part of the terminal clamp assembly. Looking at it with the clamping loop end at the bottom, the connector on the far right was missing, but there was a single wire instead that was stripped & inserted into just one female blade side of what I think is a two or three wire connector. Looking back along the wire bundle that it came from I could find no evidence of any additional wires that I would expect to see normally feeding the rest of the missing male end connector.

As I began trying to trace and separate wires I just grazed the positive terminal clamp main wire crimp (which looked like new and everything was well connected), and when I did it was extremely hot, as in branding iron hot. Waited a while and later managed to scan and check w/ Dr. Prius after restarting and allowing hybrid battery a chance to recharge w/ no accessories running, which it did just fine, up to about 65% SOC. The 12 volt battery would read on the scanner as coming back up to 14.2 volts with the engine running and at shut down, but after just 6 or 7 minutes of running the scanner you could watch the charge dropping to about 11.5, at which point the scan would interrupt, so I'd start it up, charge, and run again. It took three tries to clear the random codes and get us down to just the last two relating to the failed ABS. Red triangle would go away, but braking was definitely awry since they wanted to lock up at the slightest touch and after a few moves forward and reverse the red triangle would return and brake effort went hard. Also did not repeat the high heat condition that was present after he had run the A/C, but I didn't try that again either.

Given the miles and scan results, I was comfortable suggesting the misery of an ABS ACC replacement, but The issue of the missing connector and boogered up single wire feed is still a worry. The car looks great, but even with the new battery, there's no way the owner is gonna get out of it without taking a bath, and he's at the end of his rope with it (a tree limb fell on it while it was parked next to his house and cracked his windshield as well, just to rub salt in the wound), so I was hoping for some sage advice to pass along as to what to do about the missing connector that seems to logically have something to do with the extreme current flow or resistance effect. At this point I'm sure he'd appreciate any direction.

 

Thanks for the great reference image and response. I'm thinking my addled brain inverted what I saw, but using your picture, there was a single wire (looking at it now I'm guessing it might have been the Sense lead, as you've labeled it) that had its end stripped and it was shoved into the female receiving end to the right of the terminal clamp, which was directly under the Sense lead label that you supplied. The male end was missing, and given the size and configuration of the connector, I apparently wrongly assumed that there was supposed to be more than one wire connecting there. So much for assumptions...

The ground cable was clean and solidly connected on both ends, and the positive clamp was similarly affixed and without corrosion. The red plastic shield was missing, so the main lead crimp connection was quite visible, but it too was clean, well attached, and devoid of any corrosion or malformation. It is also where the extreme heat was exhibited, which is what led me to search for a possible skinned wire or short nearby, but nothing was obvious. As mentioned, I had no test gear unfortunately.

 

I completely agree, and had I been able I would have load tested the 12 volt, but as mentioned I hadn't thought that I was going to need the gear, so it didn't make the trip. When evaluating other vehicles with failing hybrid batteries it's proven not uncommon to see the actuation of the A/C trip a Red Triangle, but I've never had a reason to check temps on the 12 volt at that time. In hindsight, I have purchased more than one vehicle with a failing pack (as judged from Dr. Prius data) where installing a fully charged 12 volt (initially to allow me to run Dr. Prius and my scanner) permitted me to gently drive the vehicle up to 50 miles to get it to my shop without towing (but using my best hyper-miling efforts), a situation considerably impacted by the fact of living near the shore where it's flat as a billiard table. Even in that situation I've seen the fully charged 12 volt discharge dangerously low in the process, but never noticed that kind of heat.

I did remove and reinstall both the positive and the negative terminal clamps from the battery, and neither had any kind of corrosion, discoloration, or malformation. The crimps were solid, everything was clean, and once the A/C was shut down the condition did not repeat. The 12 volt battery is a 6 month old standard dealer supplied OEM replacement, installed by the dealer (I saw the receipt), but the fact of that sensing wire being stuffed bare end into the female receiver did leave me wondering, since the dealer would have certainly seen it, or perhaps they were the responsible party for why the connector was missing in the first place. The owner claims complete ignorance, and my partner has an especially deep mistrust of all things dealer related so he immediately blamed them, I guess I've not become quite that jaded, yet...

So perhaps it's just a function of a failing A/C compressor? I haven't spent any real time diagnosing electrical issues on any Prius or Camry hybrid yet, beyond pretty obvious battery concerns, so this is somewhat unfamiliar territory. Of course it's also now even more confounding since I'm trying to pass along diagnostic possibilities from three hours away.

Sticking with what I do know, I had to put the car into maintenance mode to get the 12 volt and hybrid pack to recharge enough to allow me to even run Dr. Prius or a scan. Once done the 12 volt came back up to over 14 volts, and the hybrid pack charged to 60-ish% and everything looked healthy while monitoring with Dr. Prius. I did not perform the full battery test since the brakes were acting up, and after the heating issue a life expectancy test didn't seem prudent. The 12 volt was also not holding a charge well when performing a full systems scan, and began to really drop quicker once the scan triggered the ABS accumulator/pump, and once it dropped below about 11.5 volts the scan would terminate and I'd have to repeat the whole process to be able to finally complete. The pump would also hang when doing this, not allowing me to completely shut down without disconnecting the 12 volt ground.

I appreciate the responses, but I think this is shaping up to be one of those situations where there is nothing else I can do. Like I said, the owner was a pretty decent guy who I was just trying to help out with some direction, but there are obviously limits.

If I had the car in my shop I'd test out the 12 volt battery and try one that I know is good, more closely inspect that portion of the wiring harness, remove the hybrid pack and run the Prolong regeneration process on my bench, replace the missing connector and the ABS pump. Then I'd start trying to sort out any misfires with the A/C system (which btw, scanned fine). Anyway, thanks again.