Charging system problem

[btoscano]

Yesterday I noticed my voltage guage reading at the first tick mark above 8V, it didn't go any higher when I revved the engine. It did go lower when starting. I put a VOM on the battery and it read 11. 4V (engine idling). In the past, it would idle around the first tick mark, and go up to the middle of the guaging when going down the road.



I drove the truck to a friends house and back and when I got back, I thought I'd try to start the truck so I dont' have any surprised later... didn't start. So I guess I'm looking at an alternator or alternator parts and possibly a battery? The current battery is a maintenance free type not more than 2 years old.



I searched the archives, but still have a few questions.



1. From the archives I understand that its Oaky for the voltage guage to go up and down depending on if the engine is idling or cruising? And its normal for the intake air heaters to 'click' on and off and this should dim the headlights when they activate?



2. I could not find any "box" behind my battery that looks like a voltage regulator. All I see is the horn, with one green wire connecting to it. Another green wire is just hanging. My truck is a non-intercooled 1990 with a Bosch alternator.



3. Should I replace the alternator with a Bosch? or shouild I try to change it to something else? I have no extra accessories at this time.



4. Should I look for anything else to replace? Could it be the brushes in the alternator? On my diesel Mercedes, there is an internal regulator that can be replaced and generally that's a good repair as the rest of the alternator will likely last thru 2 VR's. Is that the case with the Dodge's?



Thanks,

Brian Toscano

'90 D250 Dodge Cummins

'87 300D 332Kmi

 

[farmall]

Your voltage regulator should be located dead center of your firewall. It will have a plug with 2 wires on it. I suggest checking to see how much your alternator is putting out, pre regulator. If it is still only around 11v, then your alternator is probably bad. If it is putting out 14v+ then it is probably your regulator. Either way, I would suggest replacing the regulator. No need putting a new alternator on and skimp on a $18 part that is 14 years old.



Bill

 

[btoscano]

I think I found the regulator, two wire connector , red base in a silver colored mount bracket about 3x3 that bolts to the firewall with 2 hex bolts.



Once I get the truck started, I'll try the VOM at the the alternator.



I'm curious where the alternator wire goes? There is a connection at the battery similar ot the connection at the alternator, but it seems to go inside the truck at some point? If I disconnect the battery side, I get no interior lights & no ingition, etc...



Thanks,

Brian

 

[btoscano]

Okay, I measured volatge output at big connector on the alt. , 11. 3V just like battery side.



Measured both sides of the contacts 7 mm heads that lead to the VR... 10. 6 V on one side, 0. 58 volts on the other... . yes, that's 0. 58V on one side!



What exactly does this mean, did I test voltages at the correct locations?



I'll still replace the VR no matter what, thanks Bill.



Thanks,

Brian

 

[cerberusiam]

You need a minimum of 12v at the battery or alternator post or the battery will discharge. The large wire on alternator is the charge wire to the battery. One of the smaller wires is the field connection to the VR and the other is probably the voltage gauge wire or external ground. Not sure how this alternator works or is wired. On the older chrysler alternators you could put 12 volts from an external source to the field wire to check alternator output and whether it was the VR. Under a full load, heater fan on high + wipers + lights + high idle, the alt should put out 14. 5 volts.

 

[btoscano]

I put in a rebuilt alternator from O'Reilly's, changed the VR for good measure, and now get 14V+ at the battery. Thanks for everyone's help.



Brian

 

[bgilbert]

Brian, did you have anyone test the old alternator on a bench? I would have changed the VR first to see if that was the 'cheap' fix. Then put a charger on the battery to get it back up, and try to start again. It's good your rolling again. Bill

 

[btoscano]

Bill,



I changed the VR first and it didn't help. Then the owner of a alternator shop that's been in business for nearly 30 years benched tested it and confirmed that the alternator was not working correct.



Thanks,

Brian Toscano