Really Weird Electrical Problems - Ideas?
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Forum Name: General Discussion
Forum Discription: General Mobile Electronics Questions and Answers
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=53758
Printed Date: April 16, 2024 at 3:34 AM
Topic: Really Weird Electrical Problems - Ideas?
Posted By: Coomer
Subject: Really Weird Electrical Problems - Ideas?
Date Posted: April 12, 2005 at 2:10 AM
I'm so confused and scared right now...I can't figure out for the life of me what's going on with my car.
It started with me trying to start it after the car had sat for a week or so while I was working on engine mounts, and only the fans turning on. I checked the fuses and none were blown, so I checked the switched wire at the starter, and it was giving me no voltage.
I then unplugged the battery and went inside to take a break. When I came back out and plugged the battery back in, I noticed that the trunk light didn't turn on. I looked at the dash and the door open light wasn't on either. I tried turning on the parking lights and they didn't turn on. I tried the horn and it didn't work. Basically, nothing on the car works.
This is where it gets confusing. I've got a fuse 6" from the battery, and it's in good shape. Figuring I'd popped some other fuse, I checked all of them in the dash and under the hood, and they were all good.
I pulled the main 50 amp fuse under the hood and tested voltage on the hot side. Voltage started at around 10 volts and over a couple seconds rose to 12.4 volts and held there.
I then tried the same thing for the horn fuse under the hood, and it started at about 8 volts before rising to 12.4 and staying there.
At this point I disconnected the negative cable and came inside. Someone suggested testing voltage between the terminals and the clamps with the headlights on to test for a bad battery connection, but this yielded no voltage. At the battery terminals, I'm getting 12.4 volts. At the battery's fuse and a bolt in my trunk, I'm also getting 12.4 volts.
At this point, I'm so confused. Anyone have any ideas?
Replies:
Posted By: boomer_106
Date Posted: April 12, 2005 at 6:29 AM
The fact that you let it sit for a week immediately makes me think the battery has become discharged. I know you say it has 12.4 volts but, I would make absolutely certain you charge that battery up. Did you try jumping it from another vehicle? I would try that stuff first. Other than that since you were working on engine mounts did you have to unhook any wiring to get at them? Once again I would eliminate the battery as the concern first.
Posted By: DYohn
Date Posted: April 12, 2005 at 11:16 AM
I agree 100%. Sounds like the battery has a shorted cell, which may show proper voltage but as soon as a load gets placed on it, it cannot produce current. Take the battery to a shop for testing before you waste any time trying to charge it. ------------- Support the12volt.com
Posted By: Francious70
Date Posted: April 12, 2005 at 11:29 AM
Dead battery is what I was thinking right off the bat.
Paul
Posted By: 5150azn
Date Posted: April 12, 2005 at 11:47 AM
100 bucks says you need a better ground to either the engine block or the chassis. Ok just kidding about the 1oo bucks.
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Tell the Snap-On guy I'm not here!
Posted By: Coomer
Date Posted: April 12, 2005 at 1:48 PM
Oops,
I forgot to mention that I was also working on re-installing my alarm prior to having this problem. The alarm is currently out of the car, and there are only a few wires setup for the new install so far, and I double checked all of those wires and they're all taped up and such as to not cause shorts when I hooked up the battery.
I'll take the battery to a shop to get it tested. It's an Optima red top that's not even a year old, so if it's dead, I've got a warrantee on it at least.
And about the ground, I've got the battery in the trunk, with the negative cable grounding on an unpainted area of the trunk floor with an unpainted large bolt going through it. It's also sealed from underneath with silicone so no moisture can get in. The car is a '94 Toyota Celica.
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Posted By: 5150azn
Date Posted: April 12, 2005 at 2:16 PM
Did you check your engine block for ground since you were working on the mtr mounts?
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Tell the Snap-On guy I'm not here!
Posted By: Coomer
Date Posted: April 12, 2005 at 3:05 PM
5150azn wrote:
Did you check your engine block for ground since you were working on the mtr mounts?
Yes I did. It's still grounded. -------------
Posted By: 5150azn
Date Posted: April 12, 2005 at 6:24 PM
Can't wait to see how this story ends...
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Tell the Snap-On guy I'm not here!
Posted By: Coomer
Date Posted: April 12, 2005 at 6:50 PM
Me too. 
I'm so confused about what's going on. -------------
Posted By: boomer_106
Date Posted: April 12, 2005 at 8:20 PM
Did you try to jump it?
Posted By: Coomer
Date Posted: April 13, 2005 at 6:23 PM
I didn't try jumping it, I could though. I got my battery tested today and the guys at the battery place said it was in good shape.
Any more ideas?
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Posted By: 5150azn
Date Posted: April 13, 2005 at 6:39 PM
Still think it's a ground problem
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Tell the Snap-On guy I'm not here!
Posted By: Coomer
Date Posted: April 13, 2005 at 8:00 PM
Possibly...now that I think about it, it's possible that I'm getting a weak ground on my engine/tranny.
The reason I was working with my motor mounts was because I used to have a solid steel front tranny mount. Now I have a rubber/urethane mount instead, so the couple of ground wires that are attached to the block may not be doing their job well enough.
It tests fine with the multimeter, but maybe it's not a good enough ground for everything else. I'll have to try adding a good four-gauge ground wire to the tranny and see if that helps.
Would a weak ground on the engine/tranny cause everything in the car not to work at all though? It just doesn't make much sense to me.
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Posted By: ss-installer
Date Posted: April 13, 2005 at 9:31 PM
strange-i would jump it and see what happens. if you have a haynes manual see if the car has a starter relay or any relay under the hood. it may be bad, but jump it first, if it jumps off then its not the starter or the relay.
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Posted By: 5150azn
Date Posted: April 13, 2005 at 10:09 PM
I dunno Coomer we just got done putting a type R engine into a 93 integra and was wondering why the car started but window didn't roll up and why the engine died when the headlights were on... A week later found out that it was a ground prob. So you never know... I hope I'm right cause that would be cool; I'd know what I'm talking about for a change lol
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Tell the Snap-On guy I'm not here!
Posted By: overworked2
Date Posted: April 14, 2005 at 9:40 AM
Earth problem through and through! And I would almost say that it's a loose earth as well, suggested by the fact thatsomethings are working and then not working. Cable size will be playing a part as well if you have a faulty earth, it will struggle to get the full current down the lines and as such you. If I have read correctly. Try measuring the voltage from the (+) terminal and various earth through out the car. Anymore then half a volt (I think) is where you will have a problem. But check every earth anyways......Probably don't need to tell you this, but have you checked for corrosion inside the battery clamps? and are they done upthight? I'm sorry that I asked that but it's quite a common mistake. I have a mate who is a "mechanic" he didn't drive his hotrod for about 3 months because it refused to start, he searched high and low for the fault, he finally asked me to have a look at it for him, I gave the (+) clamp nut one turn and it started...goes to show it doesn't take much. ------------- Check all advice given with a meter
Posted By: Coomer
Date Posted: April 15, 2005 at 12:01 AM
Today I added another ground to my battery, replaced my negative battery terminal, and added a good, four-gauge ground to my tranny. I've still got the same problems.
One member on my website suggested that it may be my alternator, or the power wire going to it. The big positive terminal on the alternator gives me +4 volts currently(with the car off, of course.) Is this normal?
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Posted By: 5150azn
Date Posted: April 15, 2005 at 10:49 AM
You should still be able to jump it.
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Tell the Snap-On guy I'm not here!
Posted By: Coomer
Date Posted: April 15, 2005 at 6:34 PM
Why would jumping it help? The battery isn't the problem.
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Posted By: Coomer
Date Posted: April 15, 2005 at 11:38 PM
I tried jumping it just for kicks...nothing happens.
I found out tonight that some of the circuits in the car actually are working a little bit. When I turn the key to on, the few indicator lights come on in the cluster. Turning the key to start turns on the fans, but nothing else. Tons of circuits still don't work. I just don't know what to do.  -------------
Posted By: Coomer
Date Posted: April 16, 2005 at 3:34 AM
So today I was testing the alternator, and it turns out that I'm only getting +4 volts when I should be getting +12 volts. The wires aren't hot and the fuses aren't blown...this is really weird.
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Posted By: boomer_106
Date Posted: April 16, 2005 at 6:15 AM
How are you testing the alternator when the engine won't run? If you have an autozone in the area they will test the alternator for free. Just take it off and take it to them.
Posted By: Coomer
Date Posted: April 16, 2005 at 12:24 PM
I just tested the voltage at the large B terminal(which connects to some fuses and the battery.) So that terminal should always be at +12 volts(~14.4 if the car is on and the engine is running), not +4 volts.
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Posted By: boomer_106
Date Posted: April 16, 2005 at 8:11 PM
Oh ok. Sounds like you have just basically tested the batterys' potential through the alternator post. I'm out of ideas for ya so, I'm gonna give you a link to post your problem at. There are alot of mechanics there. They may come up with some good ideas. Just register and post your question in the appropriate forum. https://www.batauto.com/cgi-bin/Forum/db_TalkToMeV2.cgi
Posted By: joebobcletusjr
Date Posted: April 22, 2005 at 2:24 PM
Any updates on this one? I am kind of curious as to what the issue is. There has been a lot of speculation, but no sign of a resolution. ------------- eh? what did you just say?
Posted By: overworked2
Date Posted: April 23, 2005 at 9:20 PM
erm.....I would almost start looking at ECU...don't know how it would've happened but it may have. As a suggestion (and only a suggestion) you can try removing the entire loom from the ECU, leave it off for about 30 seconds, then plug it back in, then remove the (+) battery cable for 30 seconds then plug it back in and see what happens. Effectively this resets the computer and returns it back to default, if this was the problem then it should start the car. ------------- Check all advice given with a meter
Posted By: DYohn
Date Posted: April 24, 2005 at 11:09 AM
You get 12 volts at the battery and 4 volts at the alternator + terminal? Check your fusable link. ------------- Support the12volt.com
Posted By: Zen
Date Posted: April 26, 2005 at 6:19 PM
Sounds like if you have your batter in the trunk your problem is in your positive wiring from the battery to the original positive wiring on the car. You should have a full 12 volts on everything connected to the battery, including the large B terminal on the alternator. It sounds like all you have to do is find the bad connection in between.
Posted By: Zen
Date Posted: April 26, 2005 at 6:20 PM
Sounds like if you have your batter in the trunk your problem is in your positive wiring from the battery to the original positive wiring on the car. You should have a full 12 volts on everything connected to the battery, including the large B terminal on the alternator. It sounds like all you have to do is find the bad connection in between.
Posted By: Mad Scientists
Date Posted: April 28, 2005 at 8:10 PM
put down the meter and use a test light for power checking.. the meter doesn't load the circuit enough to really determine what's going on in this situation. If you want, hook up the meter to read that 4 volts, then while the meter is still attached probe the terminal with the test light. I suspect that the voltage will go away once you load the circuit. Jim
Posted By: draggindakota
Date Posted: May 02, 2005 at 9:35 AM
This may be way off base, but you said you were re-wiring your alarm right? What about the starter kill relay? If you unhooked this that could be why it's not starting. As far as the other electrical issues go, I would have to agree. It sounds like a connection problem between the relocated battery & the factory electrical. Is this a second battery or just the main unit relocated?
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