FL 70 Electrical Problems

[RichM]

I am having a weird problem that started about 2 months ago.When I first start up the batteries will not charge until I go about 100-150 miles. Voltage gradually drops and if a load is on such as lights or the AC the voltage drops quicker. Then I can drive about 2-3 hours and all of a sudden the voltage will start coming up and get almost back to normal.If I stop and let it idle for a while the batteries recover quicker. Two weeks ago I had a new alternator installed,didn't help,last night I cancelled a run from Orlando to Memphis as I had run about 140 miles and was reading 11.8 volts,turned around,started back home and after a few miles the voltage started coming back up annd when i arrived home I was reading 13 volts with all lights on.
Today I had the batteries tested with a 600 amp load across them,they tested out fine. So Back to Freightliner with a lot of concern that they will not find the problem. All of the cable connections are clean as is the main negative connection to the frame. The problem seems to get worse at speed??,This is an old 1996 truck all mechanical
so I have no idea.Any suggestions.

 

[vernon946]

Does your alternator have the regulator built-in or is it external? If external, that is a possible cause.

Did you have the engine ground connection checked with the engine cold and make sure you don't have a poor ground connection.?

When you checked the batteries, did you physically disconnect them and test individually, or check as a group? A 600 amp test can easily be passed by a group. Disconnecting also lets you check and winterproof the connections so you don't get shutdown in Burlington, VT when it is -15 deg. The voice of experience.

Carry a good voltmeter with you, and when you see the voltage dropped offf from normal, get out and physically test with the meter on the batteries. You may have a bad connection on the truck meter itself.

Good luck, and hope one of these checks will unmask the culprit.

Vernon in C2197

 

[RichM]

I believe the alternator has the voltage regulator built in.When the batteries were tested I disconnected them from the truck. Not sure about the engine ground,what is that? In addition to the truck voltage gauge I also plugged in a seperate voltmeter to a 12 volt outlet in the cab.Both readinds are the same so it's not the gauge.
Problem appears to get worse in motion.???

 

[vernon946]

>Not sure about the engine ground,what is that?

Follow the black cable coming off the battery group to the point where it is bolted to the frame or engine. Disconnect it and wirebrush the cable ends and the frame/engine mounting. Slap some vasoline on all exposed metals and reassemble.

Vernon in C2197

 

[RichM]

Did that about a week ago,no help.Freightliner called and said the truck was ready.Will pick it up today.Weave said that when batteries get about 3-4 years old they can have all kinds of intermittent problems. These batteries are only 2.5 years old so we shall see. Thanks for your advice.

 

[Jimmy]

Hey,
Rich everyone gave you good advice. Now here's mine. Have someone check each battery individually with a battery checker. Load it once then wait 30-45 seconds then hit it again. Repeat this at least 4-5 times. If one of them drops signifantly in voltage THAT could be you problem!!! Mine was doing the same as yours. Just a regular battery amp draw would indicate a good battery this test actually showed reserve holding power which wasn't much at all.
Also if any one has a "whine" in your radio ( am-fm-cb)that increases with engine speed have your rectifier diodes tested on your altenator.
In fact if your altenator is 2 years old have it tested just to be on the safe side. My theory is pay $100-200 while your at home & have people YOU TRUST to do it than be on the road some where you pay $400-600 to some one you don't know!!!LOL Jimmy

 

[RichM]

Thanks for the advice,Freightliner called and said it was a connector problem some where.I am going to get the truck now and will let you know.Only cost $98.00 so it can't be too bad. But thats good advice about the batteries to test them several times rather then once.

 

[RichM]

Problem turned out to be a faulty alternator cable connection going down to the batteries. This should have been discovered when they changed the alternator 2 weeks ago. But it was only $93.00 and the old alternator had about 280K on it so write it off to Preventive Maintenance.Thanks for all of your advice. This has made me think of something that perhaps LM could generate, a data base of problems and solutions. We all drive in the D/C class Freightliners and Kenworths and Internationals.
The B guys drive Chevys,Fords or Sprinters.Perhaps a problem/solution
FAQ could be established.Might save us all some bucks.
Go B/Sox

 

[davekc]

Yes batteries usually last 2 to 3 years. If they were completely drained at any time or have heavy frequent loads ( usually through inverters), they will deteriorate more rapidly. The difference really shows up when comparing to deep cycle (marine) batteries.
Davekc