Electrical Problems

I have a 1998 Ford Explorer 4.0 sohc. Recently I had a post that got messed up because of inappropriate posts needing to be deleted so I just dropped it and tried to figure it out myself.

Anyway, this vehicle has gone through three alternators since I think around July or August 2013. It had a sound system hooked up, but that is now in my '96. So the first alternator had about 91xxx on it when it died and I figured it was possibly an age problem. The second one was a spare that came with the it when I purchased the vehicle and had about 146xxx. That one lasted about 2 weeks and I figured it was for the same reason. I got a reman from Advance Auto and it started going out in March. Since it was under warranty, I got another one and installed it. Now with a good and fully charged battery, I had it running for 45 minutes to make sure everything was charging. The battery read around 11.7 volts with the new alternator. Is it time to tear everything apart to find a bad ground or open wire or is this a common problem that I'm not coming across? This vehicle used to be a fire police vehicle and as far as I know, the guy cut the lights off and removed the switch that was mounted under the radio. When I had that panel off I did not see anything that was remaining from that system. Could there be something further in pulling power? I also have a horn that blows the fuse after a few seconds, the fog lights do the same, and the auto dim mirror no longer works. I don't know if any of that could be related.

I don't mean to sound like a jerk or anything, but any off topic and critical, or inflammatory comments will be reported because I am for the SECOND time posting to try to get something fixed, not get lectured.

alternators tested?

11.7 volts is too low for a charged battery with the engine off and definitely too low if the engine is running.

Did you have any of your old alternators tested before replacing them? If so, did they test good?

Does your battery voltage gauge work?

Does your charge indicator illuminate when the ignition is on but the engine not running?

Is fuse 15 (7.5 amps) in the central junction box blown?

try checking the voltage at the alternator's "B" terminal (where the large wire connects to it) w/engine running and see if you get the same result. you should be reading 14+ volts at the battery with the engine running.

during your bulb check (ignition on/engine off) does your charge/batt light bulb light up? if it doesn't your alternator isn't getting switched on. your alternator will not charge if this bulb is out.

if you're getting 14+ volts at the "B" terminal but only 11.7 at the battery you have a wiring or fuse problem.

2000StreetRod said:

11.7 volts is too low for a charged battery with the engine off and definitely too low if the engine is running.

Did you have any of your old alternators tested before replacing them? If so, did they test good?

Does your battery voltage gauge work?

Does your charge indicator illuminate when the ignition is on but the engine not running?

Is fuse 15 (7.5 amps) in the central junction box blown?

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The alternators have only ever been tested in the vehicle because Advance Auto does not have the right brackets to test it in store. The battery voltage gauge does work and that is when I knew there was a problem. The gauge was reading low for a while before the battery light came on.

The battery light is on when the ignition is on and the engine is off.

I will check fuse 15 soon. Is the central junction box the one under the hood?

central junction box

The central junction box is located at the driver side door edge of the dash below the A pillar. If the charge light illuminates then the fuse is good. I don't have a 1998 wiring diagram but your wiring should be similar to my 2000. Do you have a mega fuse at the battery junction box?

Charge current from the alternator flows thru the mega fuse and then to the battery terminal. Check the mega fuse by reading the voltage to ground. It should be the same at each end of the fuse as the alternator charge terminal to ground.

some questions

I read thru the other thread and have some questions.

1. Was the sound system removed before the last alternator was installed?

2. Now that the sound system is removed does the alternator charge terminal only read 11.7 volts with the engine idling?

3. Did the vehicle as a fire/police unit have two alternators which is why you had a spare alternator?

4. Did the vehicle as a fire/police unit have two batteries and some way to switch between charging one or the other?

5. When the alternator was new and the engine idling was the battery voltage at least 13.6 volts?

If there were two batteries and some means to switch the alternator output between them that could be the source of the problem.

I have yet to test the B terminal as koda2000 had mentioned. I was going to but I could not get it started and I didn't even get a chance to get my jumper cables before it started raining so I will hopefully get to it tomorrow.

2000StreetRod said:

I read thru the other thread and have some questions.

1. Was the sound system removed before the last alternator was installed?

2. Now that the sound system is removed does the alternator charge terminal only read 11.7 volts with the engine idling?

3. Did the vehicle as a fire/police unit have two alternators which is why you had a spare alternator?

4. Did the vehicle as a fire/police unit have two batteries and some way to switch between charging one or the other?

5. When the alternator was new and the engine idling was the battery voltage at least 13.6 volts?

If there were two batteries and some means to switch the alternator output between them that could be the source of the problem.

Click to expand...

The mega fuse seemed to be fine, it had the same voltage on each side.

1. It was installed after the first reman alternator and removed before the second reman alternator was installed.

2. The reading on the battery was 11.7v with the engine running after the system was removed. As mentioned, couldn't get it started to try the charging terminal.

3. Instead of reassembling the engine that was torn apart when I bought it, I bought one with 89xxx on it that came with an alternator. The second one was originally out of the Ex. That's why there was a difference in the mileage on them.

4. I don't see where a battery could have been installed. It may have been but I don't know where it would have been.

5. For the second reman alternator, it never was higher than 12.3 volts.

How old is the battery!
Maybe it should be tested if older then a few years.
Why you are blowing fuse's with the horn and fogs lights..I have no idea unless the alt is working extra hard to charge a bad battery.

we'll need to get that "B" terminal voltage reading w/engine running to go further, but i don't recall if you had said the battery was new. as far as testing the alternator out of the truck at Advance. they're either stupid or just lazy. their testing machine has a fixture for testing your alternator. it looks like 2 fingers sticking up and slides on a metal rod. are there any other auto stores in your area? (Autozone, O'reilly's). so far i'm thinking wiring problem. do you have a wiring diagram? if not i can give you a link to where you can get one for free.

http://search.ebscohost.com/

use rrcc & rebsco to login. click "Auto Repair Reference" and enter year/make/model

BJB Fuse 14?

I suggest that you check Fuse 14 (30 amps) in the Battery Junction Box (under the hood next to the master cylinder). It feeds the alternator charge current back to the voltage regulator.

The alternator testers at discount auto parts stores do not test the alternator under load. I took my alternator to a fire engine/ambulance alternator rebuild shop and had it tested under load. The 14 year old stock 130 amp unit (with 140K miles) output a peak current of 150 amps. The "220 amp" unit I had just purchased only had a peak output of 160 amps so I returned it to the ebay reseller. I had a custom unit assembled with a peak output of 240 amps that exceeded the load capacity of the tester. Alternators will rapidly fail if operated at peak load for extended periods.

If fuse 14 is good you probably need to start tracing your actual wiring and compare it to the power distribution diagrams referenced by koda2000. Start with the charge terminal and work your way to the battery. Then start with the voltage regulator and work outward. The condition of your wiring is unpredictable after the installation/removal of the fire/police related modifications.

Dave 1955 said:

How old is the battery!
Maybe it should be tested if older then a few years.
Why you are blowing fuse's with the horn and fogs lights..I have no idea unless the alt is working extra hard to charge a bad battery.

Click to expand...

I was thinking the same thing because it makes a clicking noise as if the battery is dead. So I started my '96 to make sure the battery was good (the battery it has is just under a year old) and put it in the '98. All it does is click. I'm wondering if this is may be a wiring nightmare or if there's something wrong with the starter or solenoid now. The battery that was in the '98 before I switched them was only 3 years old anyway.

koda2000 said:

we'll need to get that "B" terminal voltage reading w/engine running to go further, but i don't recall if you had said the battery was new. as far as testing the alternator out of the truck at Advance. they're either stupid or just lazy. their testing machine has a fixture for testing your alternator. it looks like 2 fingers sticking up and slides on a metal rod. are there any other auto stores in your area? (Autozone, O'reilly's). so far i'm thinking wiring problem. do you have a wiring diagram? if not i can give you a link to where you can get one for free.

http://search.ebscohost.com/

use rrcc & rebsco to login. click "Auto Repair Reference" and enter year/make/model

Click to expand...

I know that the first response is usually that they are lazy or stupid, but this is the second time it's happened. The first time, the guy showed me the part number that their all new computerized system called for and we both looked through the drawers. It was not there. I liked their older machine better but too many of them couldn't figure out how to use it. I'm still running an alternator that they failed 4 or 5 years ago.

There's an Autozone about 30 minutes away but I was hoping to go up there for something else rather than waste a trip if for any reason they can't figure it out either.

Thanks for the link to the wiring diagram.

2000StreetRod said:

I suggest that you check Fuse 14 (30 amps) in the Battery Junction Box (under the hood next to the master cylinder). It feeds the alternator charge current back to the voltage regulator.

The alternator testers at discount auto parts stores do not test the alternator under load. I took my alternator to a fire engine/ambulance alternator rebuild shop and had it tested under load. The 14 year old stock 130 amp unit (with 140K miles) output a peak current of 150 amps. The "220 amp" unit I had just purchased only had a peak output of 160 amps so I returned it to the ebay reseller. I had a custom unit assembled with a peak output of 240 amps that exceeded the load capacity of the tester. Alternators will rapidly fail if operated at peak load for extended periods.

If fuse 14 is good you probably need to start tracing your actual wiring and compare it to the power distribution diagrams referenced by koda2000. Start with the charge terminal and work your way to the battery. Then start with the voltage regulator and work outward. The condition of your wiring is unpredictable after the installation/removal of the fire/police related modifications.

Click to expand...

Unfortunately fuse 14 is good. I will see if there's a place around here that works mainly with automotive electrical to test it. What do I need to be looking for when it comes to the wiring diagram?

96explorerxlt2wd said:

I was thinking the same thing because it makes a clicking noise as if the battery is dead. So I started my '96 to make sure the battery was good (the battery it has is just under a year old) and put it in the '98. All it does is click. I'm wondering if this is may be a wiring nightmare or if there's something wrong with the starter or solenoid now. The battery that was in the '98 before I switched them was only 3 years old anyway.



I know that the first response is usually that they are lazy or stupid, but this is the second time it's happened. The first time, the guy showed me the part number that their all new computerized system called for and we both looked through the drawers. It was not there. I liked their older machine better but too many of them couldn't figure out how to use it. I'm still running an alternator that they failed 4 or 5 years ago.

There's an Autozone about 30 minutes away but I was hoping to go up there for something else rather than waste a trip if for any reason they can't figure it out either.

Thanks for the link to the wiring diagram.



Unfortunately fuse 14 is good. I will see if there's a place around here that works mainly with automotive electrical to test it. What do I need to be looking for when it comes to the wiring diagram?

Click to expand...

look at the charging system wiring diagram. it will show you which wires you need to be checking and what they do. for instance, i believe a broken green/white wire to the alternator would mean it would never get switched on.

Yesterday I went out and tapped on the starter a few times and got it started. The voltage on the B terminal is 13.72v and the voltage at the battery is 13.65v. Not sure if the slight difference means anything. If I remember correctly, isn't it supposed to be closer to 14.3? I know the needle on the charging meter is slightly to the right of the center of the battery.

I have not checked the wiring yet because I cannot log into the site provided. Our local library used to allow you to use it but I cannot find it listed on their site any longer. Is the diagram for the Automatic Shut Down Relay here the same?
http://www.autozone.com/autozone/repairinfo/repairguide/repairGuideContent.jsp?pageId=0996b43f802d66a2

13.72 volts may be slightly low, but it's not bad. the slight difference between the "B" terminal and the battery terminal measurement is normal due to the resistance of the wiring.

okay, now i'm confused... needing to tap on the starter is an indication that your starter or starter-mounted solenoid is bad. that's not an indication of a bad charging system. what exactly is your current issue?

koda2000 said:

13.72 volts may be slightly low, but it's not bad. the slight difference between the "B" terminal and the battery terminal measurement is normal due to the resistance of the wiring.

okay, now i'm confused... needing to tap on the starter is an indication that your starter or starter-mounted solenoid is bad. that's not an indication of a bad charging system. what exactly is your current issue?

Click to expand...

If you note in one of the previous posts I said that the battery showed 12 and some odd volts but would not start so I swapped the battery thinking it may be a dead cell or two. However once the battery was switched with one that works great and isn't even a year old I thought it might be the starter. To get it to start so I could get the B terminal voltage I had to tap on the starter to get it to start. I'm not sure why it is charging now as before I had the issue with the starter, the charging meter was very low. The needle was below the battery on the meter not much higher than it was when the other alternators had started to fail.

The very last time I had it started before the starter began to go bad, I ran it for 45 minutes and after turning it off, I immediately tried to restart it. No interior lights, dash lights, radio, etc. The battery was completely dead so I had expected the alternator was bad or more likely a problem with the charging system. I guess if everything seems to be ok now, once the starter's fixed and I can drive it more, I will keep an eye on the output. Is there any chance that the starter or solenoid could have drained the battery so that it was dead after running the Ex for 45 minutes?

i don't think the starter solenoid has anything yo do with your batteries going dead. you've got too many things going on at once for me to make any kind of diagnosis. fix for starter and monitor your voltage.

Probably another one down

I have not gotten the solenoid replaced yet however it has been starting more often so I scheduled an inspection since it was out by a month (it's not my DD). Since my last post, this was the first time having it out. I think a total of 2 or 3 drives since the new alternator was put in. I noticed the battery meter was a bit lower but I figured since I was using the headlights it could just be that. So I pull into the inspection station which is only 2 or 3 miles from home, shut the lights off, and read the battery. It's at 11.8ish volts. Still nothing is installed besides a radio that did not come factory. I haven't even plugged anything into the cigarette lighter on any of these couple trips. So at this point it looks like I'm out another $100 so if possible, I'd like to get this figured out before I get another alternator.