electrical problems

[93MTXSHO_STUD]

Ok guys going back to school I noticed the old SHO seems to lose charge on the battery if it sits for a while. Say I dont drive it in 2 days the thing will be completely dead. I am thinking a voltage regulator or something is pulling current from something. These are some of the things that I have checked. I went to autozone and they said the alternator and battery were fine. I checked the all the fuses and they were fine. I got the circuit tester(aka wire and a light bulb) and probed some of the fuses in the fuse box located inside the car and about 4 to 5 lit up the bulb. Now Im not familar with these electrical systems and what fuses if any should be active with the car is shut down? Also I used the 12V comes from the factor amplifier supply and put it to my new amp. I probed that and it seemed to glow a little brighter than the other fuses. Any suggestions??

 

[93SHO'nOFF]

The way to check if you have a current draw is to measure how many mili amps it is pulling on the battery, using an DVOM meter or test light in series with the NEG battery cable and post. It should be less than 50 ma, if drawing more than than it will cause the battery to drain.Be carefull on the setting using a meter some may have a 100ma max setting and if the draw is pulling more than that it will blow the fuse inside the meter. Now the way to find where the draw is coming from is to start pulling fuses one by one until it drops below 50 ma.You can also use a test light to check for a draw but you wont be able to tell how much current is being pulled it just lights the bulb.
After finding which fuse makes it drop then start unpluging each thing that is on that circuit one by one until draw goes away. An EVTM manual will break down what all is on that fuses circuit. It's a long boring process but that's how it goes. Just be sure to pull out the hood bulb and all doors are closed while testing, if the are on it will give you an inaccurate reading. Just for an example of things I have already found causing draws are; Alternators,digital instrument clusters,amplifiers and radios,glove box or trunk lights staying on,vanity mirror lamps staying on,PCM, GEM, and Keyless Entry modules and the list goes on.One of the most common draws is that the interior light was left on. The car will have some current draw for like the clock or radio and the PCM because it has a keep alive memory so don't be worried if you see some current draw, just be sure it's not over 50 ma. Good luck and i hope it is the new amp that you put in causing the draw, it will save alot of time and headache. So i would start by unplugging that first and see if the draw goes away.
Later

 

[93MTXSHO_STUD]

Yep definitely some current draw. I'll test the fuses today. The ones in the engine compartment dont draw current so thats a plus! This shouldnt be too hard since I'm an EE major and this is cake compared to the stuff I have to build like this semester a GPS controlled RC car that has to circle a parking lot and not hit any curbs!

 

[93MTXSHO_STUD]

Will all the fuses in it pulled 450mA. The only fuse that made a difference was a 15A fuse that was in the #8 spot and it dropped it down to 380mA. So thats a 70mA draw on components which is in range... a little high but i have a stereo system and such so this is expected. Now the 380mA I dont know where its coming from? I'm assuming its the voltage regualtor in the alternator? Has anyone had such a problem? The alternator has about 135K on it, and still charges the battery fine!

 

[93SHO'nOFF]

You can condem the ALT If you unplug the voltage reg and unbolt the 12v wire from the back of it to see if the draw drops below 50ma, 380ma is still to high trust me, i have a system in mine also and it doesn't pull that much.I will check the EVTM for what #8 fuse has on its circuit. Hey, did you try unplugging your amps to see if it goes away?

 

[93SHO'nOFF]

What year SHO is it?

 

[93SHO'nOFF]

Oh and also you should have the meter hooked up to the battery post and the cable before you take the cable off the battery so that the circuit isnt open then closed again with the meter,it will reenergize some of the relays causing an in accurate reading.

 

[93MTXSHO_STUD]

I did all the testing with the amp disconnected. I replaced the alternator because autozone said it was bad on there little test. I didnt physically check it, but the bearings were for sure bad and with it having 135K on it i guess it wasnt a bad idea either. I have a 93 SHO MTX. With the new alternator it still pulls .41amps or 410mA. This weekend im going to do some starter testing and soleniod testing as well using my Mulitmeter. I am stumped really right now. I mean I pulled all the fuses and such.

 

[93SHO'nOFF]

I did all the testing with the amp disconnected. I replaced the alternator because autozone said it was bad on there little test. I didnt physically check it, but the bearings were for sure bad and with it having 135K on it i guess it wasnt a bad idea either. I have a 93 SHO MTX. With the new alternator it still pulls .41amps or 410mA. This weekend im going to do some starter testing and soleniod testing as well using my Mulitmeter. I am stumped really right now. I mean I pulled all the fuses and such.

Hey man check your messages.