Posted May 10, 20178 yr I'm going to be installing a stereo for my buddy in his JDM 1991 Mitsubishi J53 Jeep Turbo Diesel. The original radio was AM/FM with push in pre-set buttons (reminded me of my dad's old '67 Ford Galaxy 500XL Convertible). He's got some marine 6.5 coaxial speakers/pods he's mounting on the roll bar behind the driver and passenger's seats. The electrical is 24V (2 batteries wired in series). He bought a cheap no-name bluetooth media player and a 24V/12V converter. I know the fused "constant" wire from the stereo will connect to the 24V/12V converter but where do I get the 12V for the "ACC" ignition and remote/antenna wires from? All the wires shoot 24V-27V with the key in the ignition and in the "ACC" position. If I tap into one of these wires, will it fry the stereo? I don't think it'd be a good idea to have all the wires from the 24V/12V converter (constant 12V) running to the stereo. Thanks in advance for the help.
May 10, 20178 yr Author I forgot to mention the converter only has 2 wires to the 24V side (+ & -) and 2 wires out of the 12V side (+ & -).
May 10, 20178 yr I would wire the stepdown on a relay and attach the trigger wire to the key switch, then attach the radio constant and accessory wire together to the 12v side of the stepdown so you can have a switched source. I can draw a diagram if you'd like.
May 10, 20178 yr I would wire the batteries in parallel and series and use the 12v for the stereo. Way simpler. Btw, I drove a 68 Galaxy XL over 300,000 miles
May 10, 20178 yr Author M5, Can you explain the parallel and series a little further? I like simple...Do you mean that I can use one of the 12V batteries positive (the overall 24V positive) and negative (the negative connected to the other battery's positive in the series configuration) without effecting charging and not need the converter? Where do I get a 12V wire for the ACC so not too have constant power to the stereo? Or the 12V battery positive (overall 24V positive) and use the vehicle frame as the ground for 12V and use the converter for the ignition wire? I measured the voltage of all the wires (in the connectors) going to and coming off the ignition on the steering wheel and it read 27V. I think my dad's Galaxy had 200,000 miles on it? He just drove it in the summer, usually to go golfing. I used to call it "the tank" because of it's size. I did like cruising with the top down!
May 11, 20178 yr You should have no need for any converter. It's HIGHLY unlikely the electrical system is 24V, but the starting and charging systems will be. This is common with commercial tractors. The rest of the system should be 12V. Even if it's not, you can just pull 12V from one battery; no converter needed.
May 11, 20178 yr Author My buddy is mountain climbing (Mt Rainier) so I'll have to wait until he gets back to check the wires again.
May 25, 20178 yr Author My buddy got back and I went over there and shot some wires. I did find one that was 11.92V (with key in ignition turned to ACC). I think it was a remote wire to the old stereo. I used a wire tap and connected it to the remote (blue) and 12V ignition (red) wires on the stereo harness. I didn't use the converter. I thought I was good to go... Mistake #1- I told my buddy to connect a ground wire from the battery negative terminal to the frame. I should have checked after he was finished. He connected it to the 2nd battery negative terminal (which made my voltage 24V instead of 12V, correct?) Mistake #2- I was rushing and didn't check the voltage before hooking the battery back up. Needless to say when I connected the battery back up it took about 2 seconds before we heard 2 pops and saw white smoke coming out of the head unit. The inline fuse didn't pop nor did the fuse in the back of the head unit. So my question is, if I run a ground wire from the 1st battery negative (which is connected to the 2nd battery positive) to the chassis, will this be the fix so I don't smoke check another head unit?
May 25, 20178 yr If he connected both negatives to ground, you would have a direct short. Hook the batteries up. Take your meter and measure at the battery you are grounding to chassis. Between that ground and the positive post of that battery you should have 12V.
May 30, 20178 yr Author So I ran the both power and ground wires straight from the one battery (not grounded to the chassis) to the head unit. Measured voltage first before hooking up the stereo...12.92V. Connected the rest of the wires and no pops, smoke, or burning smell. Everything works! Now, the stereo doesn't turn off after the vehicle is off and key removed from the ignition. The ACC and antenna wires are tapped into the old remote wire for the old stereo. It reads -12.92V with key in the ignition and in the "ACC/ON" position, and 12.99V when the vehicle is running. We also noticed the fan can be turned on/off after the vehicle is off and key removed from the ignition. When he turns the fan off, the stereo turns off, too. I'm going to work on it again tomorrow. Any ideas...?????? Edited May 30, 20178 yr by firey_kimchi mistyped some details
May 30, 20178 yr Is the accessory on power 12v? If so, use that one. If not, an el cheapo Bosch relay connected using the 24v to pass the 12v will work.
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