Both headlights burned out tonight... Why?

[Green Monster]

I removed the bolt in the center. I tried to remove either side. These things will not come apart. The entire bracket starts coming through the wall. Could it be melted together? It looks good from the outside.

[jaros44sr]

You will want to pull towards the engine compartment, mine stayed with the firewall, I dont know why it wants to go into the interior

But it may not have ever been apart, so that makes more difficult. Your right it mite have melted somewhat, be careful not to damage it, your doing good. I would hate to see you break something at this point

I just checked mine and the fuse box side is tyed to the firewall securely, probably bolted .... J

[Green Monster]

I am pulling from the engine compartment toward the front of the Blazer I'll give this another shot. I'll hold the large bracket while I pull the plug.

[jaros44sr]

Don't know of a large bracket, unless your talking about the brake booster support rod, LMK

Just looked at my firewall plug side, and that bolt is all I can see that holds the 2 halves to getther. Once you get that plug off it will separate into 2 rectangular boxes

[Green Monster]

Okay. Got it. So I disconnected both halves of the plug from the firewall, as in, it they are removed from the firewall. Checked negative side of my battery with my volt meter. I placed the meter inline of the ground cable and negative terminal. 9.95V is my reading on a battery reading 12.5V. What does this mean?

I did check my alternator while the engine was at idle before disconnecting the firewall wire harness. It was putting out 13.6 volts. I'm not sure if that helps.

[jaros44sr]

Your going to have to back to 72lb4X4's post and try to understand that, I don't follow it but it is lenghty, maybe you'll have better luck, try to follow his directions because I have never had a spark on the neg. side of the post. Must be something with one of your grounds???? J.

[Green Monster]

Originally Posted by 72lb4x4

If you suspect a current draw while everything is turned off, you might try disconnecting the wiring harness connector at the firewall. It bolts on under the hood by the master cylinder.

Test again with the light, or with an ammeter connected where the light was.

What is the current drawn?
What is the voltage on the battery with the engine running and off? This is more to give an indication of the battery/charging status.

What is connected to the junction block where the small positive wire from the battery on the fender? Normally there's a red and black wire there that go into the wiring harness, accross the core support, and so on. Other wires indicate creative wiring. See the wiring diagram:

http://67-72chevytrucks.com/vboard/s...d.php?t=185856

If your light goes out with the firewall connector disconnected, the problem is under the hood. If not, try disconnecting the read and black wires from the junction on the fender one at a time.

If current is still flowing with both wires disconnected from the junction, something is strange ;(

The fusible link by the battery in the diagran is supposed to stop the carbecue, BTW...

Now that I got the beast to run, I can answer these questions with hope of your help.

12.5V at the battery from post to post when the engine is not running.
13.4V at the battery from post to post when engine is running.
10.5V at the battery from - post to ground cable when engine is off.

This is a two battery system. I was told by the previous owner that Blazer had a winch on it which the second battery supported. That battery is dead. It will not charge. It reads 0.2V so I disconnected it completely so it would not interfere.



The junction I have two junction blocks on the passenger fender and one on driver side fender.

I removed the wire harness from the firewall as stated. The volt meter still reads 10.5V going from the negative post to the ground cable. I do get sparks when connecting the ground cable.

With 3 junctions I will have to look closely at what goes to where. I can follow up tomorrow when I have some daylight to work with. According to you directions and questions, that is the next step to complete.

-John

[crzngmychvy]

Man, I've been trying to follow this thread but it makes my head hurt.

I respect your commitment, but when I found myself in the same situation I gave up after one weekend and took it to the shop. When all was said and done I asked him to install a really cool kill switch too! That's just me though.

[old man jimmy]

Man, I'm sorry I missed all this. Was gone all evening & just got home. Soooo glad you got it up & running again. See it wasn't so hard. As far as getting a spark when you hook up the cable. All that tells you is something is on. Clock, doom light etc. First off I would check your aux. battery cables. What did you do with them? And what kind of a rig did the po have for charging both batteries? Do you see something that looks like a ford starter selenoid? If both batteries were hooked up. That's probable what drove your regulator crazy. One being dead. And yes you are persistent. But sometimes that's what it takes. I for one am proud of you for finding your miss matched wires. Im still a little suspect of your 4 yr. old battery. Do You have one you can set in it to see if it sucks the juice out of it? Hang in their guy, you're making progress. As far as you charging voltage. It's perfect. Went back a couple posts. All 72lb4X4 is descibing to you is a way to find out if your drain is under your hood, or behind where you unpluged the firewall conector. Sounds like yours is under the hood.

[Green Monster]

Originally Posted by old man jimmy

1. As far as getting a spark when you hook up the cable. All that tells you is something is on. Clock, doom light etc.

2. I would check your aux. battery cables. What did you do with them?
And what kind of a rig did the po have for charging both batteries?

3. Do you see something that looks like a ford starter selenoid? If both batteries were hooked up. That's probable what drove your regulator crazy. One being dead.

4. Im still a little suspect of your 4 yr. old battery. Do You have one you can set in it to see if it sucks the juice out of it?

5. Went back a couple posts. All 72lb4X4 is descibing to you is a way to find out if your drain is under your hood, or behind where you unpluged the firewall conector. Sounds like yours is under the hood.

Responses to the above statements and questions.
1. I'm still getting a spark on the negative battery cable while the firewall plugs are disconnected. So, as you stated in no. 5 that I listed above, it does seam as though my problems are under the hood. I am just thinking here...

My problem may be from "creative" wiring from a previous owner that ran wiring for something like, oh, I don't know, a stereo amplifier for a pair of sub woofers that used to be behind the back seat before I bought it. He may have just cut the wires and shoved them under the carpet before he sold it to me. Would that cause my drain if it were still live and touching a metal object like the floor. I have only found some 16ga.speaker wires so far. I will dig deeper this afternoon.

A tow hitch was installed with a plug connector by the PO. Again, looks to be some creative wiring back there. But if the connector at the firewall is disconnected and I'm still having draining problems with the ground cable connected to my battery, I would venture to guess that is not my problem, right?


2. The cables for the driver side battery (extra) are simply disconnected for now. They were connected when the headlights blew. I will trace these wires an update my post this afternoon to tell you exactly where they go and how they PO had them connected. All I can tell you right now is that I have three junctions. One on the driver side fender, and two on the passenger side fender.

3. I have not seen a Ford starter solenoid. I would recognize one as I have replaced on in my Mustang in the past.

4. I'm suspect of this 4 year old battery as well. I can set my battery from my Mustang in there and give it a shot. That is about 4 years old too though.

5. I agree. My drain sounds like it should be under hood, or directly wired to the battery. I should just start tracing wires to see where they go. Sounds like some insulation might have worn thin near a metal part. I really don't know at this point. But with PO's handy work, I suppose anything is possible.

[jaros44sr]

You can take your battery to a parts store, they will check them for you, and make sure those wires running under your rug are dead

[Yukon Jack]

So glad to see you're making progress - I'm very electrically challenged so I'm trying to use this post to educate myself some. I will be book marking it for future reference.

[red71cheyenne]

Ya, with the bulkhead connector disconnected, that doesn't mean you've killed all the power. I know I have power running around it in several places and stereo's are notorious for having separate power leads running to them. If it is under the carpet and shorting to the frame, that could be one of your drains. About your only hope now, is to start taking a look at all the wires that are running under the hood and see where they all go from the junctions. Your dead battery probably is the end culprit, but you may have other issues that caused it to go dead, ie. the drain from something shorting to ground. Good luck and let us know if you need more help! Jeff.

[old man jimmy]

Could it be you had this drain problem before your headlights went south? How often do you use the truck? The woofer wires you discribe, I see no reason for them to have started being a problem because your lights went out. Could be melted insulation on a couple wires inside your wire harness. But before I spent too much time on searching your harness. I would deciede if you want to keep your dual battery setup. (myself I would. Nice back up) If you do I'd replace the dead aux. battery, hook it up and go from their. Been 30 some years since I've worked on aux. battery hook-ups, so memory not wat it once was. But I would fix all known problems before I started looking for new ones. The ford selenoid thingy I was talking about. Your hot (+) wires from batteries would go to it. If you don't want to keep dual batteries, then we'll talk you through wireing it for one.

[Green Monster]

I removed the dead battery. Then I disconnected the + cable from the charged battery and placed my volt meter inline of the ground cable and the - post. The meter still showed 10.5V. I thought that was strange. I moved the battery to my Mustang and placed the grounded the black wire on the meter to the strut mount and placed the red wire of the meter to the - post. I did not touch the + post. Same result: 10.5V. Looked to me like the battery had shorted, or something. Seemed strange to me.

I went back to the Blazer with no batteries in it. I traced the wires from both batteries. I will create a diagram using the Microsoft Visio program I have at work then post it. There is too much going on to try to describe. The diagram would work a lot better. I found one wire coming off a junction block that had the insulation worn off in two locations. It was apparently wedged between the driver side battery and the radiator support. It had grounded it self to the support. I tapped that one to protect it for the time being.

So decided to pony up some bucks an purchase a new battery since my old battery appeared to have signs of a short since it read voltage to the ground regardless if the + post was connected or not. I brought home a new battery and plopped it in. Connected the + cable and then connected the meter to the ground cable and the - post. I got a reading of 12.5V.

I disconnected the cable from the + post then checked the meter again. 0.0V. That was a good sign since my old battery showed a 10.5V when grounded no mater what.

So I then connected the + cable, disconnected the bulkhead harness, and then connected the meter to the ground cable and the - post. I got a reading of 0.0V. That tells me I either have a short inside the cabin or the radio is drawing power for memory. I will investigate further tomorrow by disconnecting my radio.

Things are looking up though. I think I understand what happened now. The battery on the driver side died. The voltage regulator was allowing a charge to both batteries since they are connected in a series. The driver side battery would not take a charge so the charge was being accepted on the passenger side battery which became overcharged and shorted. This is when my headlights blew too. The voltage regulator may have failed too. I replaced the voltage regulator.

I plan to eliminate extra battery along with the damaged wiring to the extra battery. I do have some questions about a hot connection on the radiator support wall. Both pink wires from the batteries run into the connector (picture 1) then one wire goes to the fuse block. That pink wire comes back out of the fuse block (center most of picture 2) to the tach. A brown wire comes out of the tach and leads to the fuel tank.

I would like to just eliminate this connector at the radiator support and run one battery wire straight to the fuse block. This would eliminate two junctions, one connector in picture 1, and one battery. What do you think? I can create a diagram of what it looks like by tomorrow afternoon, then make another of what I want to do. Could you walk me through the process, old man jimmy? Should I just follow the wiring diagram linked a the beginning of this post?

Picture 1



Picture 2

[Green Monster]

Here some additional pics of this crazy set up for those interested.
Passenger side. Battery removed.


Damaged wire linking batteries.


Driver side. Battery removed.

[Green Monster]

I don't see anything on this wiring diagram about going from the battery to the fuse block. This appears to more "creative" wiring.

Originally Posted by farside847

Here are some higher rez versions to view online:

[old man jimmy]

Sounds good. But look back at your last post. You stated you had a meter reading of 0 volts on ground with firewall plug plugged in. And 0 volts with firewall plug unplugged. But you think you're still getting a draw from something inside your truck. Unless that's a typeo, You don't have a problem anyplace. So time to quit unplugging wires, like radio. Remember what happened last time. Be glad to talk you through getting rid of your aux. if that's what you want to do. But if it were me, I'd just get another battery for the aux. side. I used to use mine for camping, and always wished I had a dual battery set up. When you're up in northern Nevada, 70 miles from anything, it's nice to have a back-up. I even order mine with 4 speed for that reason. I can always find a hill to roll start it. You can make them fail safe with a switch between batteries so they can't do what yours did again. But like I always say. Make them the way you want them. Forgot to ask. Is that a factory option or add on? Should say on your glove box door.
Tom

[Green Monster]

Originally Posted by Green Monster

So decided to pony up some bucks an purchase a new battery since my old battery appeared to have signs of a short since it read voltage to the ground regardless if the + post was connected or not. I brought home a new battery and plopped it in. Connected the + cable and then connected the meter to the ground cable and the - post. I got a reading of 12.5V.

I disconnected the cable from the + post then checked the meter again. 0.0V. That was a good sign since my old battery showed a 10.5V when grounded no mater what.

So I then connected the + cable, disconnected the bulkhead harness, and then connected the meter to the ground cable and the - post. I got a reading of 0.0V. That tells me I either have a short inside the cabin or the radio is drawing power for memory. I will investigate further tomorrow by disconnecting my radio.

I have a reading of 12.5V through the ground when the bulkhead is connected.
I have a reading of 0.0V if the positive post is disconnected.
I have a reading of 0.0V if the bulkhead is disconneted while the positive post is conneted.

I'm not sure about the factory option or add on. I will check this afternoon. If it was factory, I would like to keep it, but have it wired up right.

[old man jimmy]

Ok guy, You are talking 12.5 volts from ground to ground, right? If your reading goes to 0 when you unplug your firewall connector, should be simple to track. If I'm reading this right, your drain has to be behind your fuse block. Time to start pulling fuses, ONE AT A TIME. And check your voltage at ground each fuse. Then put that fuse back in, and go on to the next. When you find the fuse that gives you a 0 reading at ground, see what it says it's for. Should tell you where to look. Check any unfused wires plugged in at fuse block also. Just make sure to plug them back in where they were. By the way, Just noticed something. When you were testing this & that with the hot (+) cable off, all that was telling you was that the battery had a shorted cell, and when you hooked the ground up to metal you supplied a path for the current to flow to. You would have got your 10.5 volts or what ever it was, if you had hooked the cable from the ground on battery to a metal workbench, fence or anything metal. I had never heard of testing for a short that way, but hey. Now we know a new way for testing a shorted battery. I have a regular battery tester, but for you guys that don't, you might want to keep it in mind. Seems to work. See never too old to learn.
Tom

[Green Monster]

That is correct. When I unplug my bulkhead connector my drain drops from 12.5V to 0V. Sounds pretty simple to narrow down from what you told me. I will investigate further to determine where my drain is. Looks like I'm on the right track. Should have this thing figured out by this afternoon since I have the day to work on it.

That shorted cell was messing me up. All my testing was pointless with that bad battery in there. I never had a shorted cell, nor did I know one could exist. Now I can go about tracking the drain down with all the instructions all gave me earlier.

My earlier post about the wire going to the tach then the full tank may be wrong. I have to check that wire again. What's the deal with all the wires coming out of my fuse panel? Was this all "creative wiring" or is it supposed to look like that?

Initially all these wires all over the place were a bit overwhelming. Now that I know where they go to and from it makes it a lot easier to comprehend what's going on here. Most of my problems appear to be from wiring that was done by previous owners. This electricity issue is really not that intimidating anymore when the wires are easy to track down.

Dealing with electrical issues is a task in of itself. Giving advice for electrical issues is pretty difficult. What would possess you guys to give electrical advice to someone who has no clue what he is doing?!!! Thank you for all your help so far, everyone. I have enjoyed this learning experience.

-John

[old man jimmy]

Good luck today. We're all learning all the time. I have a question for you. How did you have your meter hooked up when you were getting your 10.5 volt reading? And are you sure you're not talking amps. not volts? And from what I could tell from your pictures. Your battery set up looks pretty factory. I've got a shot battery setting around in the garage. I'm going to see if I can get some juice in it, and try your battery test. I think you may have stumbled upon something their. May not be a new idea, but it's new to me. See, I learned from you. You fuse panel has had a few wires added, but all of our has. Looks to me that he did a fair job of it though. And your tach wire should go to your - side of your coil. Or connect to that wire someplace.
Tom

[jaros44sr]

100 posts and 4 pages and your all done, painless....

My opinion, you should put that switch in to separate the batteries, like Ol' man jimmy suggested....probably will never happen to you again but ...

Glad it all worked out work, you were on a steep learning curve with the world watching J.

[Green Monster]

Originally Posted by old man jimmy

I have a question for you. How did you have your meter hooked up when you were getting your 10.5 volt reading? And are you sure you're not talking amps. not volts?
Tom

I just took the back wire from my meter and touched it to the - post on the battery. Then took the red wire and touched it to metal part on the Blazer. The meter is digital and can measure ohms, vots, and amps. I just set the wires up on the meter where they need to be and select what I would like to measure. I bought it at Home Depot. I was definitely set up to measure volts, not amps. My meter was not registering anything when attempting to measure amps.

[Green Monster]

Originally Posted by old man jimmy

But if it were me, I'd just get another battery for the aux. side. You can make them fail safe with a switch between batteries so they can't do what yours did again. But like I always say. Make them the way you want them. Forgot to ask. Is that a factory option or add on? Should say on your glove box door.
Tom

I checked the inside of the glove box and the auxiliary was a factory option along with the hand throttle cable on the dash. So I have decided to keep the auxiliary battery option. I prefer to keep the Blazer stock, with the exception of the lift wheels and tires. So how does this fail safe switch work? How do I set it up?