80 Series Electrical Nightmare... Help!

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Mar 2, 2016
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Memphis, TN
Hey guys,
I recently bought a 96' LX450 with around 176k on it and a T-MAX dual battery system. It's just about as solid of a truck as you can find mechanically, but I've been experiencing some crazy electrical problems that seem to get worse as the weeks go on. I've done crazy amounts of research on the forum, but have yet to find one that meets my criteria. Any advice or help is greatly appreciated. Here it goes...

On the first day I bought it, as I turned the key at the gas station from acc to start, I lost all electrical power to the vehicle (dash lights, wipers, etc..). All I had to do to regain power was to go under the hood and disconnect and reconnect the ground off of the main battery and everything seemed to be back to normal as it was when I test drove it. This did not happen again for a couple of days and I didn't think much of it.

Things started to get interesting when after a couple of days this became the regular start-up process. I would go under the hood, disconnect, reconnect, then link the dual batteries and it would start right up no problem. I had read on the forum that some other users had experienced this as a product of a bad battery, so I swapped the battery from my 97' collectors edition into the Lexus and it changed nothing.

After swapping the Lexus battery back in, the T-MAX system won't link the two batteries and shows constantly full voltage on both batteries and that it is charging the main. It will now start but its VERY weak, and I have to try turning the key from acc to start a couple of times before the starter will engage.

(charging blinks which you cant see from the image)

I'm gonna drop a couple more pics in the thread just for reference, but I'm at a loss of ideas here. The previous owner was nice enough to help me try and solve the issue, but we had no luck. All and any advice is greatly appreciated.

Thanks so much, everyone. I hope you all are well and safe with all of this madness going on.

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Joined
Mar 2, 2016
Messages
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Memphis, TN
I can't see any of the attachments. That being said, I would start by temporarily just making the vehicle run on a single battery as in a stock setup. And depending what results you get, go from there.
Attachments should be up now. Thanks for the help.
 
Joined
Mar 2, 2016
Messages
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Memphis, TN
I can't see any of the attachments. That being said, I would start by temporarily just making the vehicle run on a single battery as in a stock setup. And depending what results you get, go from there.
Switched to main battery only and I'm back to the click when turning the key from acc to start. I'm losing all power and have to go under the hood and disconnect and reconnect. Clicks consistently. Won't start. Any ideas?
 

voodu3

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How does your fusible link look? I would check all of your grounds and the power wire to the starter. There maybe a loose connection that is getting contact after you reconnect the battery. This is just a WAG but I’ve had electrical issues that were solved clean grounds and solid connections.
 
Joined
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Messages
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How does your fusible link look? I would check all of your grounds and the power wire to the starter. There maybe a loose connection that is getting contact after you reconnect the battery. This is just a WAG but I’ve had electrical issues that were solved clean grounds and solid connections.
Fusible link is good. I'll check the grounds and power wire in the morning. Thanks man.
 

ppc

M Go Blue
 
 
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Switched to main battery only and I'm back to the click when turning the key from acc to start. I'm losing all power and have to go under the hood and disconnect and reconnect. Clicks consistently. Won't start. Any ideas?
If you mean you used the T-MAX to switch to the main battery then that is not what @Cruzerman has recommended. Disconnect that device completely so you return to stock. Have you checked voltage directly at the battery? Have you cleaned the battery terminals and neutralized corrosion from battery acid with a baking soda and water solution? Still have the problem then jumpstart using jumper cables from a know good battery.
 
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If you mean you used the T-MAX to switch to the main battery then that is not what @Cruzerman has recommended. Disconnect that device completely so you return to stock. Have you checked voltage directly at the battery? Have you cleaned the battery terminals and neutralized corrosion from battery acid with a baking soda and water solution? Still have the problem then jumpstart using jumper cables from a know good battery.
Disconnected the TMAX system completely. Battery terminals are clean (It's pretty much brand new). Even with a jump it does the same thing.
 
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Yep, until it works on just one battery, things will stay confusing. Most of these systems give you the choice of main battery, auxiliary battery , or both/linked. If you can only start when linked, then there is an issue somewhere with the inter-battery wiring or the T-Maxx unit itself. That's why you need to start (we hope) by verifying it will start on the battery Mr. T gave you.

OK, saw while writing that you think you've disconnected the T-Maxx unit itself. But there's likely more wiring that connects ti it that regulates the battery charging circuit, plus some sort of link to the starting circuit. You'll need to check for those connections. And most parts stores offer a free battery test if you're not confident in reading it at home. When was the last time that primary battery was changed? If it's more than 4 yo, then that's a likely culprit here, although far from the only possibility.
 
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replace the fuseable links, they can corrode internally and cause similar hard/no start conditions. I had the same issue and some times the truck would start some times it needed jump other times it was try again in about 5 min and no problems. I cut the old liknks open and it was just white corrosion dust in there
 
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Yep, until it works on just one battery, things will stay confusing. Most of these systems give you the choice of main battery, auxiliary battery , or both/linked. If you can only start when linked, then there is an issue somewhere with the inter-battery wiring or the T-Maxx unit itself. That's why you need to start (we hope) by verifying it will start on the battery Mr. T gave you.

OK, saw while writing that you think you've disconnected the T-Maxx unit itself. But there's likely more wiring that connects ti it that regulates the battery charging circuit, plus some sort of link to the starting circuit. You'll need to check for those connections. And most parts stores offer a free battery test if you're not confident in reading it at home. When was the last time that primary battery was changed? If it's more than 4 yo, then that's a likely culprit here, although far from the only possibility.
I could have easily missed some other connections in the TMAX system. Primary battery is a year old, however when I swapped in the brand new battery from my other 80 I had the same issue. I'll check those wires in the morning. Thanks!
 
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replace the fuseable links, they can corrode internally and cause similar hard/no start conditions. I had the same issue and some times the truck would start some times it needed jump other times it was try again in about 5 min and no problems. I cut the old liknks open and it was just white corrosion dust in there
Fusible link looked to be okay, but I think I have an extra one that i can throw in. Thanks man. You have good taste in names. We like to call the collectors edition Big Red.
 
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Fusible link looked to be okay, but I think I have an extra one that i can throw in. Thanks man. You have good taste in names. We like to call the collectors edition Big Red.

unfortunately they look good till you cut them open, just kinda how it is with them and for the cost of a new one its one less thing to rule out when diaging and I keep one in the glove box as a spare at all times. good name for a truck
 
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I could have easily missed some other connections in the TMAX system. Primary battery is a year old, however when I swapped in the brand new battery from my other 80 I had the same issue. I'll check those wires in the morning. Thanks!
Yeah, voodu3 is helping you out with that wiring diagram. Looks like there is a somewhat different philosophy in how they hook things up in that they put most of the loads on the auxiliary battery, then they protect the main so you always get a start -- when it's working.

First thing I'd track down is that 2 amp fuse in the line to the solenoid. Verify it's good, the follow the wiring out from the solenoid. Try to confirm it's wired like the diagram or if not verify if it has something else happening. I use the H*llroaring dual battery set-up and they recommend a 50 amp circuit breaker in the charge line to the batteries. never had a problem with that, so your 2 amp fuse here seems a bit dicier, although it's hooked up differently so may be fine.
 
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Messages
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Yeah, voodu3 is helping you out with that wiring diagram. Looks like there is a somewhat different philosophy in how they hook things up in that they put most of the loads on the auxiliary battery, then they protect the main so you always get a start -- when it's working.

First thing I'd track down is that 2 amp fuse in the line to the solenoid. Verify it's good, the follow the wiring out from the solenoid. Try to confirm it's wired like the diagram or if not verify if it has something else happening. I use the H*llroaring dual battery set-up and they recommend a 50 amp circuit breaker in the charge line to the batteries. never had a problem with that, so your 2 amp fuse here seems a bit dicier, although it's hooked up differently so may be fine.
Yeah, the 2 amp is good. I've checked it at least 3 times now. As for the rest, I trust the previous owner who wired it, but I'll for sure double-check with that diagram. Thanks.
 
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I'd agree with the above regarding the fusible link. Best to put a fresh one in there to eliminate that variable.
 
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Memphis, TN
Read the fusible link with a meter. Reading 10v. Both batteries reading 12v. All grounds looking good. Would it make sense that it may have something to do with a faulty starter relay?
 
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