Just need a little help. Have an 02 Ram 3500 wont crank until it is placed on a battery charger with a start circuit or left on charge over night. I have replaced the batteries twice, left and right battery cables have been replaced, starter has been replaced, checked fuses and the relay they're all good, cleaned all ground connections put dielectric grease on them. At a serious loss on this. Starts fine if its been sitting on the charger overnight. Some days doesn't need the charger some it does. Have put a meter on the starter and when when the key is turned over there is no draw at the starter or batteries. batteries are both 12.7, 12.8. Any help would be appreciated.

How did you check the relay?

just swapped the relay

Gotcha. I know you said you replaced the batteries, but it still might be worth putting them on a load tester. The whole thing doesn't make a lot of sense.

 

I could give a billion guesses but the part with the battery charger has me a little confused, especially since the 12.8 volt charge. I would disconnect one of the batteries and check the voltage again after a few minutes.  The batteries, while both connected, will measure the same since they are connected in parallel. In theory, one bad battery could cause similar symptoms.

1 minute ago, kzimmer said:

Gotcha. I know you said you replaced the batteries, but it still might be worth putting them on a load tester. The whole thing doesn't make a lot of sense.

 

I could give a billion guesses but the part with the battery charger has me a little confused, especially since the 12.8 volt charge. I would disconnect one of the batteries and check the voltage again after a few minutes.  The batteries, while both connected, will measure the same since they are connected in parallel. In theory, one bad battery could cause similar symptoms.

Ya thats the problem on my end to it doesn't make sense me!! I have had both battery's disconnected and measured both are 12.7 and 12.8. I wasnt convinced so I made them replace the batteries under warranty again. lol someone at the parts store wasnt happy!!  Thats why I took them back a second time because they did a load test and it showed good. I made them them do a load test on the new ones before I left showed good, but the issue with the load tester is it may not show an internal short in the battery, should but seen where they havent.  have also disconnect my heater grid just for shits and grins to see if that had anything to do with it. I thought maybe a large draw maybe causing the issue however my batteries do not go below 12.7 after sitting all night. I have also had the new starter tested and it was good. 

I should have added more when I say just clicks its the bendix you can hear engage but the starter wont turn.

Have you tried jumping the starter relay from another power source?   

 

Get a multimeter setup to measure if there is an amp draw when the truck is off. 

It sounds like a weak conection and requires more juce just to crank it over. Does it only do it in the morning after truck set all night, or every time you go to start it. 

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13 hours ago, Dieselfuture said:

It sounds like a weak conection and requires more juce just to crank it over. Does it only do it in the morning after truck set all night, or every time you go to start it. 

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Its intermittent. sometimes it will start and sometimes it wont. Not just the mornings. 

Thanks 

jsmyer

22 hours ago, Me78569 said:

Have you tried jumping the starter relay from another power source?   

 

I would probably go here next. Try to rule out ignition switch. Or clutch switch if it's a manual. If it's an auto throw it in neutral and try.

Monitor your battery voltage while you're cranking/or attempting to crank it over. If your batteries are reading high then it's a bad connection between batteries and starter. If voltage drops way down then bad batteries. All my dodges with 2 batteries (and or diesels) have always seemed to get a lot of corrosion on the cables, sometimes to the point that I'd have to build some new cables.

This might be of some help :

 

 

The common failure is the starter contacts...