Charging system question

[Asploderfan]

So I've been a member here for awhile but post very little. Almost every question or issue I've had was answered or gave enough guidance to figure out my question. Here's one I could not find: My Exploder is a 97 XLT with the 5.0. It is not charging. For the last month or more the dash gauge (not sure if volts or amps) was reading low at low speeds but would come up when the RPMs came up. Recently it quit charging at all. My DMM reads battery voltage at the B+ post on the alternator while the engine's running. No bueno, I know. The gauge reads low now and does not come up with RPM. What I'm cornfused about is that the little idiot light of the battery is not lit. If the alternator wasn't alternating wouldn't the batt light be on? It does light up when the key is on like the other indicators.

 

[koda2000]

if the BATT/CHG light bulb on the dash is burnt out (or not working) the alternator will not charge. does the light come on during the bulb check?

that bulb is lit by the battery and is turned off by the alternator's voltage regulator by breaking the ground connection for the bulb.

if the bulb is good/working it should come on if you're running off your battery (alternator not charging). other than the serpentine belt, the alternator is really easy to remove to take it somewhere to have it tested. most auto parts stores will test it in their machine for free.

 

[bobflood]

Just had the same thing happen - battery not charging over time but "BATT" light is not on. I got a voltage measurement of about 12.5V at the generator output; should be at least 14V. I believe that what is happening is that the generator is putting out enough power to run the vehicle and keep the BATT light off, but not enough to keep the battery charged.

This was an aftermarket unit from Advance Auto with a lifetime guarantee installed 9/2011, so they replaced the unit at no charge. Took me about 1.5 hours to change it out - hardest part was finding a way to finagle the serpentine belt tool onto the tensioner to remove the belt. There is not a lot of room between the face of the tensioner and the back of the fan. A "short" 15MM 3/8 socket would help - I need to find one. Good luck.

 

[koda2000]

Tip: If you remove the intake tube between the air box and the TB, you have a lot more room to work. I took my belt tensioner loose with a 3/8 breaker bar and a shallow 15mm socket. I had my daughter help me get the belt back on the new alternator. Probably took me 20-30 minutes to swap he alternator out using air tools. It was actually easier than I thought it was going to be.

 

[bobflood]

I took the intake hose off, but AC line and radiator hose still in my way. I didn't have anyplace to swing the bar far enough. I ended up doing it from underneath. I think the shallow socket is the key - have to get me a set.

 

[intelisevil]

Tip: If you remove the intake tube between the air box and the TB, you have a lot more room to work. I took my belt tensioner loose with a 3/8 breaker bar and a shallow 15mm socket. I had my daughter help me get the belt back on the new alternator. Probably took me 20-30 minutes to swap he alternator out using air tools. It was actually easier than I thought it was going to be.

Adding to those tips, remove the darn air box too! That gives you even more room to work. I actually removed/replaced the alternator through the vacancy where the air box had been. I replaced the serpentine belt at the same time, the hardest part of the entire project was looping the new belt under the crankshaft pulley. No special tools needed, just used my basic Craftsman socket set.

I was in no big hurry, it took me about 45 minutes from popping the hood (no air tools) to washing my hands. My dog was "helping" so I had to stop and play with her too. I had the core back to the store quick enough that they asked me if there was a problem, I told them they had given me the wrong part! Then I opened the box to show the old alternator and asked for my core deposit back. Some people have no sense of humor . . .

 

[koda2000]

Adding to those tips, remove the darn air box too! That gives you even more room to work. I actually removed/replaced the alternator through the vacancy where the air box had been. I replaced the serpentine belt at the same time, the hardest part of the entire project was looping the new belt under the crankshaft pulley. No special tools needed, just used my basic Craftsman socket set.

I was in no big hurry, it took me about 45 minutes from popping the hood (no air tools) to washing my hands. My dog was "helping" so I had to stop and play with her too. I had the core back to the store quick enough that they asked me if there was a problem, I told them they had given me the wrong part! Then I opened the box to show the old alternator and asked for my core deposit back. Some people have no sense of humor . . .

For some reason, replacing the serpentine belt always drives me crazy (I've done it 5 times). I know how it's routed, but trying from the top or the bottom I always have trouble getting it around the fan correctly on the first try. I find that's the toughest part because the fan is so close to the shroud. I don't know, I must be doing something wrong, but I never get it on the first try.

 

[Asploderfan]

Hey, guys, thanks for the replies. I checked output voltage at the B+ post on the alternator, it matched battery voltage and didn't come up with the engine running so I took the alt down to the parts store and had it tested. Tested bad so I took it apart. I had rebuilt the alternator last year, new rotor, bearings and voltage regulator, the diode bridge was the only original part left aside from the case. Some of the points where the stator is soldered to the diode bridge were melted. Got an alternator from a wrecking yard for roughly 1/3 of the cost of a rebuilt from the parts store, I will swap the new parts from the bad alt to the wrecking yard unit at my leisure. I was just curious about why the 'batt' light did not come on. BTW, the serpentine belt is pretty easy to negotiate with a tool from good ol' Horror Freight for serpentine belts, I found it easy to do from the bottom. Swapping the alt took about 15 minutes including getting the air boot out of the way.

 

[koda2000]

Hey, guys, thanks for the replies. I checked output voltage at the B+ post on the alternator, it matched battery voltage and didn't come up with the engine running so I took the alt down to the parts store and had it tested. Tested bad so I took it apart. I had rebuilt the alternator last year, new rotor, bearings and voltage regulator, the diode bridge was the only original part left aside from the case. Some of the points where the stator is soldered to the diode bridge were melted. Got an alternator from a wrecking yard for roughly 1/3 of the cost of a rebuilt from the parts store, I will swap the new parts from the bad alt to the wrecking yard unit at my leisure. I was just curious about why the 'batt' light did not come on. BTW, the serpentine belt is pretty easy to negotiate with a tool from good ol' Horror Freight for serpentine belts, I found it easy to do from the bottom. Swapping the alt took about 15 minutes including getting the air boot out of the way.

You never answered the question - Does your BATT light come on during the bulb test (engine off key in ON position)?

 

[Asploderfan]

You never answered the question - Does your BATT light come on during the bulb test (engine off key in ON position)?

It is in the original post:

So I've been a member here for awhile but post very little. Almost every question or issue I've had was answered or gave enough guidance to figure out my question. Here's one I could not find: My Exploder is a 97 XLT with the 5.0. It is not charging. For the last month or more the dash gauge (not sure if volts or amps) was reading low at low speeds but would come up when the RPMs came up. Recently it quit charging at all. My DMM reads battery voltage at the B+ post on the alternator while the engine's running. No bueno, I know. The gauge reads low now and does not come up with RPM. What I'm cornfused about is that the little idiot light of the battery is not lit. If the alternator wasn't alternating wouldn't the batt light be on? It does light up when the key is on like the other indicators.

But, yeah, it did come on with KOEO.

Edit: BTW, I dig ur sig.

 

[koda2000]

It is in the original post:



But, yeah, it did come on with KOEO.

Edit: BTW, I dig ur sig.

sorry, I missed that - and thanks.