Author Topic: weird electrical issue.  (Read 1678 times)

rodmankn3

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weird electrical issue.
« on: December 26, 2018, 11:11:46 PM »
So, my 1999 3.5L SOHC Monty is acting up. My girlfriend called that the truck would not start after shutting it off. she noticed that the radio started flickering and stopped at a gas station. it was still running, but as soon as she turned it off it would not start. I got there and it acted like it had a dead battery (battery is a week old and alternator about 3 month old). I connected a meter and battery had 12.7 volts. I connected my jumper kit and immediately the alarm went off. after starting the truck the meter was reading 14.1 volts, so the alternator seems to be working. I started driving it home (1 1/2 miles) and halfway there I noticed that the radio, compass and gauges, some dash lights started flickering. then the vehicle power started cutting in and out, like if on a rev limiter. it stalled again when I came to a stop. I jumped it and it started but it would not idle unless I gave it gas. the whole way the power is cutting on and off. I also noticed that when applying the brakes the dash flickers and when the engine cuts off I hear a clicking sound from under the passenger dash area.
 
 Help me troubleshoot this. could it be the factory alarm acting up? ECU craping out?

Let me know what you think and were to start. I did change the alternator because it stopped charging, I think oil got to it. and then the battery would not hold a charge if I did not use the truck for 3 days. so I bought a new one.

 :-\ :-\ :-\ :-\

Crumb

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Re: weird electrical issue.
« Reply #1 on: December 27, 2018, 05:54:03 AM »
If the alternator is a reman from some auto parts store i'd start there, I've had more than a few bad out of the box and one that caused an issue like you're describing. Mine eventually started blowing 100amp fuses, was really hard to diag until the smoke leaked out of said alternator. You'll eventually get a good one under warranty but it could take some tries. Hope this helps.

Shovel

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Re: weird electrical issue.
« Reply #2 on: December 27, 2018, 09:18:19 AM »
Something I've been noticing on the three Monteros I spend the most time working on lately - our wiring insulation is getting brittle under the hood.     

I'd suggest giving your wires a really good look-over, particularly the ones closest to/on top of the engine and closest to the battery.   

rodmankn3

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Re: weird electrical issue.
« Reply #3 on: December 27, 2018, 11:04:48 AM »
Yeah it is a remanufactured alternator. will keep that in mind.

I'll do a check of the wiring.

 one thing I did this morning was to check continuity of the battery cables. I noticed that the insides were not to clean and in some areas I was not getting continuity unless I really dug into the terminal. I cleaned the terminals and attachment points in the body. I charged the battery to make sure I have a good charge. car started right up. noticed that alternator would not drop below 14.5v at the battery terminal. also, when warm the idle would not hold and she would stall. I'm checking the TPS, idle control valve and general adjustments. after that I'll check the alternator.

Shovel

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Re: weird electrical issue.
« Reply #4 on: December 27, 2018, 11:20:27 AM »
While you're checking the wiring on top of your engine to the coils & ignition transistor,  also check that the ignition capacitor is in place.   That protects the vehicle's electrical systems from inductive noise from the coils and the wiring to it is sort of fragile.    If the positive side shorts to ground it can make the engine stall (bypasses the ignition transistor = no sparky)

rodmankn3

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Re: weird electrical issue.
« Reply #5 on: December 27, 2018, 04:21:00 PM »
Update, I adjusted/ checked TPS and idle as per the FSM. it was out of whack. TPS does have one ear cracked( not fully). Idle control vale was cleaned but it feels a little gritty when I pushed by hand. the TPS connector is brittle, lost the wire spring to hold it in place firmly. so far no issues.

will check that ignition capacitor, any pictures or diagram to see how it looks?

Shovel

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Re: weird electrical issue.
« Reply #6 on: December 27, 2018, 05:11:25 PM »

will check that ignition capacitor, any pictures or diagram to see how it looks?

This is something we just went over with Nick's Montero incidentally - on top of the engine are your three ignition coils,  they have the big spark plug wires on them but also the small wires which lead back from them to the main  harness.    Inside the harness they are mostly kept parallel and tight so even if the insulator becomes brittle it has nowhere to go.    But between the harness and the coils there are many exposed wires which go to the coolant temp sensors, the ignition transistor, the ignition capacitor, etc -  all in a bit of a birds' nest up there.       

Additionally the wires under the main fuse panel under the hood (below/beside the battery) seem to wear on each other and get exposed - possibly due to exposure to battery acid over the years or just vibration - it's not a bad idea to closely inspect the insulators on those too.     

rodmankn3

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Re: weird electrical issue.
« Reply #7 on: December 28, 2018, 07:42:53 PM »
Noted, Thanks a lot.