Charging problem with new Alt

[mfitz725]

I Put on a new alternator on my 94 XLT and also had the battery checked. Sometimes the gage does not show the system is charging. Today I've had to jump it off plus if the headlights are on the radio goes off and the turn signals come on but don't flash. Battery terminals seem tight and can't find anything broken. It makes me think of a relay sticking somewhere since part of the time it shows charging and everything works fine and no Jumpstart is needed. Does anyone have any ideas?

 

[Centaurious]

Battery cables are a well known problem, check both the frame and body grounds.

 

[mfitz725]

I Checked the charging rate and it is only 11.9 volts. Took the new alternator back and exchanged for another and now am getting a charge rate of 12.6 to 12.8. I thought anything less than 13.8 was insufficient. So far can't find anything wrong with the battery cables but will need to get underneath it to check some more. Is there anything else that would keep the alternator from charging at the proper rate?

 

[CDW6212R]

I agree about the battery cables, check all ends and replace any non stock terminal connectors. Those bolt on type are poor, temporary items.

For the alternator, unless the battery is completely charged, with no other loads but the engine it should take close to 13.5 volts at idle. Different loads or idle speeds, or underdrive pulleys etc, all reduce voltage figures.

FYI, you can use the later model alternators of the 95-01's, the 4.0 OHV(same engine) units. I had a spare 1999 alternator from my truck, which I put on my 91 Explorer. It worked great, showed a little better voltages(stronger unit from my Limited(140amp)). Those are 3G alternators, they can be upgraded easily by local shops.

 

[toypaseo]

My 2¢... check the battery cable inside the battery terminal. I had problems with turn key, click, and everything dead. Corrosion inside the battery terminal was the issue. No problems since I switched to aftermarket 100% brass terminals and treated battery terminal felt washers.

 

[natenkiki2004]

Check the voltage at the battery (terminals) with the engine running, then check it at the alternator (positive post and engine ground). If there's a significant difference like half a volt or more, your cables need help and likely replacement.

 

[mfitz725]

Check the voltage at the battery (terminals) with the engine running, then check it at the alternator (positive post and engine ground). If there's a significant difference like half a volt or more, your cables need help and likely replacement.

It really strange. I start the vehicle and it is charging at 12.2-12.6. If I drive for a while the voltmeter gage will sometimes start going over to the middle. If I stop and check it's charging at 14.5. Sometimes it never stops charging above 12.6.

Do you know where the battery cable attaches to the body? I can't seem to find it looking from the top. I just don't know what could be causing this problem.

 

[natenkiki2004]

No need to hunt around to see where the cables attach, just check the voltage like I outlined above. If there's a difference then you know you need to look at the cables and likely replace them. There's a thread on that here:
http://www.explorerforum.com/forums...94x-battery-cables.250186/page-3#post-3309529

But if you do occasionally see 14v, it may be yet another faulty alternator that's not kicking in at idle speeds.

 

[mfitz725]

No need to hunt around to see where the cables attach, just check the voltage like I outlined above. If there's a difference then you know you need to look at the cables and likely replace them. There's a thread on that here:
http://www.explorerforum.com/forums...94x-battery-cables.250186/page-3#post-3309529

But if you do occasionally see 14v, it may be yet another faulty alternator that's not kicking in at idle speeds.

Thanks for the thread link but note none of the pictures are still available.

 

[natenkiki2004]

Sorry about that, I've fixed it.

 

[mfitz725]

Sorry about that, I've fixed it.

Found the charging problem and quite by accident. Threw the serpentine belt on the interstate last night and limped into a McDonald's. Happened to have purchased a new belt the day before because I thought it was making noise. Managed to get the wrapped up old one off and new one on under one of the parking lot lights. Imagine my surprise when I cranked her back up and the volt gage showed charging normally. Apparently the old belt was worn enough that it wasn't turning the alternator at full speed.

 

[natenkiki2004]

You might take a look at replacing your tensioner and idler pulleys as well. They're pretty cheap and will make the new belt run tight and true.

 

[larrydd999]

Thanks for 'closing the loop' with your finding. That would certainly explain why you were getting various voltage readings.