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Hi, I'm Chad. Welcome to JustAnswer. I'm reviewing your question and I will be posting your reply ASAP.
have you went back and checked all the ground connection from the frame to the engine block ?
how does it run ?
have you checked for 12 volt on battery
and 14 volts when running with all loads on ?
Please let me know
ASE Certified Technician
I will open up your question for another expert for you, they might have more/better info on this issue.
Hello and welcome to just answer and allowing me to assist you. I see in your notes you said you checked the alternator and seems fine? the problem when diagnosing electrical problems is when the issue is not occurring everything will show good, so with that being said you have to try and simulate the problem which in some cases is either difficult or not possible to do. the other option is to have a volt meter hooked up to read it when it happens. By what you are describing is a voltage surge and can be caused by bad connections, loose or damaged drive belts, faulty relays, alternator --diodes and voltage regulator. You can do a few visual checks as the drive belts , check for any corrosion on electrical connectors , when running have someone sit in the vehicle as you wiggle all the wiring in the engine compartment to see if that triggers it. The last thing I would recommend is to have a full AVR test done on the charging system this may trigger that symptom, it will also show you if it has any weak diodes in the alternator and how the regulator performs under load and RPM. from idle to 2500 rpm . Hope this gives you a direction to solve your issue and if you requier any further assistance I'll be happy to do so.
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