Hey y’all! So I’ve been doing a lot of digging but can’t decide what to use or get for options on upgrading my 85’s alternator after getting a full alarm and stereo system professionally done I had him check the grounds and all my grounds were good or replaced so I know I still have a stock alternator which when I use my lock and unlock it kills the charge and I can’t start it so I’m figuring it’s the alternator because it’s completely stock. battery and alternator were checked and tested good so I’m thinking a new alternator upgrade should help not unless anyone has some suggestions on what could cause that to happen but I’m going alternator route because it’s really old so what should I replace it with?

 

Sounds much more like a battery related problem. Bad/corroded terminals, bad cables, down inside the insulation type failure, etc. You said you got it tested, but did they load test the battery? Did they check the water levels in the cells? It sure sounds like it can't take a short term drain on it.

A bad alternator wouldn't charge the battery adequately. It would show as a low charge while the truck is running. If the battery voltage is low when it's NOT running, though, most likely an old, worn out battery.
​​​​​​​You can check it yourself easily. With the truck running, check the volts at the battery across the terminals. If it's less than about 13.5VDC at idle, yeah, alternator. If the volts are good, bad battery. Also, check the connections on the alternator. Especially the big, heavy bolt connector on the side. That's where the power to charge the battery comes out. Do you have more volts there than at the battery? Bad cable, or connection.

So yeah, there's a lot of checking you can do without throwing parts at it, hoping for the best. A multimeter can save you a lot of money and frustration. They're very inexpensive. Well worth picking one up.

Just my few thoughts...
Pat☺

 

No I don’t have more voltage than the other Both were checked and charged up, both held a charge and were good maybe I just have old wires my battery is like a year and a half old so I’m thinking maybe not I really don’t know how old my alternator is so it’s probably stock and should be replaced otherwise

 

I've had bad luck with the high amp direct fit alternators from LCE, etc. They put a smaller pulley on there which caused my rig to consistently throw the belt around 4500 rpm or so. Also the cost is crazy considering it's not uncommon to blow up the alternator when messing with the radiator hoses. There are two different stock options, a 40amp and a 60amp, but your rig may well have the 60 amp on there if it came with power options. If I were trying another high amp setup I'd swap to a one wire setup. Pretty sure there are some how to threads. But also I don't think door locks should drain your battery...maybe check for chewed up wires in the door jamb?

 

only reason I’m thinking it’s the door locks is because the door locks are hooked up to the alarm and when I press the lock it flashes the lights with it so with alternator being so small that the alarm system drains enough volts where the car can’t start. Correct me if I’m not wrong

 

Oh yeah I get it now, my alarm system also drains the battery. How long does it have to sit before it won't start? You might try measuring amps at the battery when the rig is fully turned off to get a sense of how much the drain is. The batteries in these trucks are pretty small, that may be the problem.

 

I did the upgrade on my 86 with a GM alternator. Liked it and did it again to my 84. The wiring was a bit tricky until I figured out how to do it cleanly. After that it was a cake walk

 

I’m thinking a day if not 2 days that the battery gets to the point where it just clicks

 

Is this a one wire alternator setup or 3 wire?


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It can be a 1 wire, but you have to rev it over (I think) about 12-1500 rpm to kick it off. It won't take off at idle and charge. The small red wire is a sensing wire (not always needed, usually looped to the alt/batt post on the alt), the yellow is from the toyota ignition to start it charging at idle (factory) also makes sure to turn off the batt light in the dash, the black wire is a ground (not always needed, but I was just being cautious) and the large red is alt to batt.