So i've been tracing out some electrical issues on my supra, one thing first off is im not sure if it's an 87 or an 86.5, it was made in august 86 so im thinking its an 86.5 but im not positive...Anyways, First off my alternator isn't charging the battery, I've traced out my wires and checked continuity up to the fuse block where the connectors plug into the fuse block and all of them are good, also i've checked the fuses and relays and flasher because i have no turn signals, no hazards, and no winshield wipers. I've replaced the battery and the combination switch assembly (turn signal/headlight switch, and wiper switch) with one that i got from a junk yard with the wiring harness and all. So i've been tracing some of these issues out and yesterday it would crank and run fine (excluding that the alt is not charging) and today when i went to start it up to move it into a better place to work on it i've got no crank. The car has power and my battery still has 12.38 volts on it so i know its not an issue of having killed the battery. The lights will work, and when i turn the key to the accessory mode i've got power, as soon as i go to crank...Nothing. Im kinda at a loss at what to look for at this point...i've checked and rechecked everything that i was looking at today before i went to move the car and everything is plugged up like it should be and the fuses are good. I know i've got a small list here, but anything that you guys can think of would be extremely helpful. Thanks to all in advance. Oh, and i do have the haynes manual so i've been using it to trace the wires out.
Tracing out electrical issues, now no crank
- Thread starter thagber
- Start date
Lose the Haynes and use this:
http://www.cygnusx1.net/Supra/Library/TEWD/MK3/manual.aspx?S=Main&P=038
http://www.cygnusx1.net/Supra/Library/TEWD/MK3/manual.aspx?S=Main&P=038
When you turn the key, do all the lights dim and you'll have a starter click?
Could be a bad starter relay or even a bad connection between the battery and the starter.
Could be a bad starter relay or even a bad connection between the battery and the starter.
what jetjock said.... Also put your key in the driver door and lock and unlock it a few times there is a chance you set off your alarm this will turn it off if so
As a side note, you should lose most electrical power to accessories and lights when trying to crank the engine. This is true on almost all cars.
Yes you can bench test a relay
Or you could drop test it in place
Sent from my C811 4G using Tapatalk 2
Or you could drop test it in place
Sent from my C811 4G using Tapatalk 2
there is a write up, but there's mixed feelings about it. most of the people that did the relay mod had intermittent issues, mine just stopped working yesterday. i'd love to be able to diagnose the "Real" problem, but being colorblind makes it pretty hard to do electronics. 
I've done the relay mod and haven't had any issues since and it's been a year and a half now. If u don't wana go that route, u can always check resistance in the power wire to starter solenoid. Also, try removing the 20amp fuse underhood for dome light. If it starts up, it's a good possibility that ur anti theft is activated