Kingunis

I just picked up a 92 sc400 a few weeks ago and on the drive home the radio (aftermarket pioneer unit) cut out 3-4 times while driving home it would just turn off for about 1/2-1 sec and then come right back on. It hasn't done this since that day and i daily drive this car everyday well today i decided to put some new front speakers in so i did and tested it after and everything worked just fine, drove it around and everything no problems at all. later on my buddy came over so i decided to show him how it sounded and about 2 min at a medium volume the radio just turned off everything else works in the car electrical wise so i thought the headunit took a dump. I decided before i bought a new one to plug my friends brand new pioneer unit in to see if it worked and still the new radio wouldn't turn on so i pulled the dash apart to check the ground which was all good i then checked the fuse under the hood and under the drivers side dash and both are good and all the wiring for the radio looks to be crimped properly and all there any ideas what could be the problem?

Teal Sc400

It could be that you need a new radio control switch? I've noticed at times/occasionally, when I turn my headunit/volume *** I get no sound. I proceed to lower volume/ turn volume up having sound produced. It may be the problem?

Kingunis

I assume your talking about the stock radio volume **** on the side with the temp ****. the stock volume **** is bypassed I'm pretty sure since it did nothing when the radio did power on, right now i have the console apart so that **** is unplugged and still the head unit will not power on

Biddles

iTrader: (2)

Sounds like a bad ground, I would redo every connection. That's really what you need to do. Start by getting a new ground wire. I don't care what's there, replace it with a slightly higher gauge in a new location. Use a grinder, file or dremel to remove the paint and make sure you have a perfect ground.

I couldn't find a good place to put the ground wire in the dash, it's pretty tight and hard to work in there, so I wired mine near the passenger side pillar, great spot and I have a high powered system(1000wRMS). People say use a close ground, but I couldn't find one and I have no problems with the 6 foot ground wire I'm running.

Also I replaced the negative batter terminal, $11 shipped on ebay for a factory replacement. Just search for this :TOYOTA OEM Battery-Terminal 9098206022". I'm sure the ground was my problem, but it doesn't hurt to replace a 20 year old terminal while you're at it.

Don't trust someone else's connections, make your own.

eknine9

iTrader: (8)

^^^^
Like Biddles said the grounds behind the radio are notorious.
When I got my car the aftermarket unit there would take 7-8 minutes to turn on when it was cold outside.

Eventually I took the dash apart to replace my creaking head unit harness and do the touch-screen climate control and the ground was atrocious. It was just a wire held onto a painted surface with a nut at the top right of the firewall, and I suspect that may have been the factory ground due to this being a common problem.

I used the same grounding location, but I got a ring terminal that I sautered and clamped my new ground wire to, and sanded the metal bare in that location till it was nice and shiny for a good connection. I get the feeling, the true ground is through the bolt at the back of the dash that the nut was on, and not directly on the metal of the firewall, but I think the ring terminal provided a better connection to the nut and bolt, and the sanded metal was a just in case kind of thing.

Ever since then my head unit no longer cuts out, or doesn't turn on and there's a second identical bolt on the top left that I did the same thing to and used as a ground for my touchscreen climate control. I'd suggest anyone with head unit problems go back there and check the grounds.

Also like mentioned above, upgrading the battery ground with a bigger gauge wire can help facilitate current flow as well.

Kingunis

yea ill give that a try since i tried to follow the 2 power wires form the head unit to see if they were messed up and they looked fine, the ground wire on mine just goes straight down and is under a bolt right in front of the transmission which looks like it has a lot of paint on it so ill try replacing that and see where it gets me

eknine9

iTrader: (8)

Yeah get rid of any paint on the contact surface, it impedes current flow. You can do it with just a bit of sandpaper and some elbow grease.

Kingunis

so i didn't get a chance yesterday to put a better ground in but why i had few moments i decided to take a better look at the current ground which i realized whoever grounded it before already sanded the area down of all the paint(didn't get a good look at it until now). i figure i would check how he grounded wether it was a metal ring or just a wire wrapped around a bolt so i started to unscrew it and noticed it was a ring so for the mean time i just screwed the bolt back down. Now just for ****s and giggles i tried the radio again so i plugged the headunit back in and then i plugged in the stock radio control switch and when i turned the car on the radio powered on and stayed on for about 20-30 seconds and then just cut back off for good again. I'm gonna upgrade the ground wire today to better location and thicker wire so hopefully that fixes everything

BlackIRON

I had a similar problem after i hit a tough bump my radio turned off then on again then off and never came back on. I pulled it out and moves the ground to a better area on the driver side metal and it worked. My fuse was not blown or anything i guess its kind of a natural occurence? Anyhow try moving the ground or making sure it has a good contact.