Hey everyone,

have an 02 7.3L 250 ambulance package (2 alternators)

the upper alternator is new as well as both batteries. Lower alternator was replaced 2 years ago.

the truck shows the system charging 13.8-14.4V then sometimes randomly stops charging kills the accessories and kills the batteries after awhile.

I can’t seem to figure out what’s going on and was hoping for ideas??

any help would be greatly appreciated

thank you!

 

Have you installed a new radio ??

 

No I have not. After several more attempts discovered that the new alternator and several replacements were all bad. Charging the system seems to be resolved but every now and then the interior lights/dash/radio go out and then come back on after a short period.

 

I cannot speak to the intermittent on off - but I have a dual alternator GM 6.5 - and on dual alternator systems it is important to make sure the alternators are MATCHED. They need to be the same amperage rating and both have the same regulator rating - both be 14.3 matched set for example Even the manufacturer being different will cause one regulator to NOT follow the other and one alternator will just cut off believing the batteries are charged or being over charged. This is really evident if one is a 14.7 set point and one is a 14.3 set point. If the stators are different amperage rating this can also happen.

Believe it or not I use twin Ford Style F540 XHD Regulators which are a 14.3 set point at the factory and can be opened and underneath there is a pot screw to adjust them to follow one another if need be. Usually you do not need to.

Follow means the alternators work in unison as they are one maintaining a set voltage both putting out amperage

With Standard flooded wet cell batteries - different brands take a charge at different rates and also may discharge at different rates given age and CCA rating - and this will cause the regulators to act up also. AGM batteries are a bit different.

You do not say what kind of batteries you have - but if you have AGM batteries , be advised they are usually not flooded wet cell frm the factory - only enough electrolyte is put in to "WET" the fiberglass mats in between the plates. Sadly - these do and can dry out enough that the batteries will not take and hold a charge. The plan is for this to happen just after the warranty runs out - but hot charging the batteries with over 14.4 volts will make it happen faster.

This will cause the regulators to cut off also - as the battery resistance appears to be low enough to stop charging - but the reality is they are not charged and never can be.

I once worked at Globe Union - Johnson Controls in Milwaukee WI where the battery plant was until Johnson sold it. In development the higher ups did not want to put these AGM units on the market because the performance was too good and they lasted too long - until they modified them to only have wet AGM mats between the plates. I have dual battery sets - six batteries in all - three standard flooded wet cell for external to start the engine only - and three for internal use - off which are all AGM that can take deep cycle discharging. I can let the internal batteries deeply discharge to 12.4 to 12.3 volts and flip them onto with the starting batteries with a marine switch over switch and start the engine because the external batteries are still fully charged, and then watch the amp meter as the dual alternators fast charge the entire bank. A full charged battery will reject current when it is sent - so the current automatically goes to the depleted AGM's which charge about four times as fast a standard flooded lead acid batteries. When everything is charged I can see the alternators cut off - and there is zero amps out of them - and I can touch the regulators and they begin to cool from being warm from in the follow me regulation mode.

BUT the point of all that is to say my AGM batteries would not work properly of have decent CCA readings either until I opened them and FLOODED them full of standard battery acid. Normally people tell you to use distilled water - but in the case of AGM batteries - they never had enough electrolyte in the first place so it is standard battery acid which is about 1.2 SG - NOT concentrated Sulfuric Acid which is 1.6 to 1.9 SG which will actually eat the plates. Distilled water will kill the battery in this case.

If you have something like a Foxwell BT-100 electronic battery measurement device you will see the CCA come up by itself, and when charged an AGM battery which floats at 13.1 volts may actually hold 13 to 12.9 volts once settled down and they will take a charge really fast.

At least that is my real world experience and it does not matter if it is a Ford, or GM - this is how dual alternators work