I have a early 99 7.3. The past couple weeks the batteries are dying if I skip a day of driving it. The batteries are from 2022. Today I jumped it off like I typically have had 2 after letting it sit a day or two and about 2 minutes after I unhook the jumper cables the truck dies and throws a Service engine light and I got no wait to start light.
I just replaced the CPS, and ICP both with OEM parts. Aside from the truck needing to be jumped every 2 days it’s been running great for hours at a time. Can a bad alternator cause the truck to stall and throw a SES light? I don’t have access to a multi meter right now but just wondering if that’s possible. I have tried jumping it off again and it cranks but no start. No wait to start light. Service engine light is on. While I understand this could be a lot of things, would the past couple of weeks having dead batteries lead you to think alternator? Or is that possible with a SES light? Sorry for rambling

 

I always keep Battery Tenders on my vehicles.

Quit throwing parts until you have found out WHY the battery is going down.

Why in the hell would you think the CPS is running the battery down?

Get a Clamp On Ammeter and trace the current draw

 

I was just saying it’s already been replaced I didn’t think it’s causing the battery to die. I was just canceling out what everyone always says it’s could be. Those parts were replaced in the last month for actual failure. I’m just wondering if a dead alternator can cause my service engine light to come on and the truck to stall. That’s all…
Typically when I get a Ses light and a no start it’s a symptom of cps or icp, yet they are brand new. Could this be a symptom of a bad alternator also considering my truck has died multiple times over a 48hr period

 

From what you've described I would think a bad alternator could be part (or all of) the problem. You are going to need a multimeter to check for 14v+ coming off the alternator.

I just replaced my alternator, it was not the easiest thing to diagnose as the first few times I tested it I got 14v, but it would cut out periodically.

I didn't get a CEL, but I did get a battery icon that would light up once in awhile. Truck never died while running, but my batteries never got fully drained.

 

You have a huge parasitic draw.

Get a multimeter, and conduct an parasitic draw test.

Given that it is going undernight, my huge suspicion is you have a bad alternator diode, which is drawing your power town. This does not replace the parasitic draw test but disconnect both power plug, and battery wire on the alternator and see what happens.

 

Going to need to throw the batteries on a charger as well. Supposedly not good to let the alt try to charge the batteries when run too low. They are really only to keep batteries topped off, not to be used as chargers

 

Yep I forgot that part.

 

Thank you all for the responses. I’m not a mechanic but this info being shared is priceless and helps me out a lot. I will check everything shared so far. The weird thing about my 99 is anytime there is an issue regardless of how small I get a check engine light and no start.

 

More so on the e99, these trucks are subject to water sneaking in (thru a bad windshield seal or roof cab markers) and making it's way down to the fuse box & GEM area. It may not be a river, but the cumulative effects could be corrosion in the fuse box bus bars. This corrosion would allow some short circuiting of switching and things will be on (continually or intermittently). It is the classic "gremlin" issue and I had it in my e99. This included random horn blowing.

I had the same prob as you: after it sat for a day or two without use, the batts were drawn down. In addition to the intermittent hassle, my heater blower would be running, even if the switches were both off. Coupled with cold weather (-25F), this was just enough to force me to jump start the thing. And before I got a true grip on things, I changed the otherwise good batteries (in retrospect, they were 2.5 yrs old at the time).

Your specific issue of no WTS light, etc. did not present with me. But all bets are off when those bus bars get filled up and give all sorts of options for unwanted current to travel, or not travel.

Showing one of the layer separators.

Typical layer of busbars. The corrosion lives at what is the lowest point of the box when mounted.

These are the quickest photos I have. But there are several layers of busbars. Some areas were more corroded than what is shown here and there was layer to layer "fusing".

​​​​​A parasitic draw test will point you in the direction of the above type of problem, or whether your alternator is the source of the draw (if it is truly a draw issue). Although the alternator will likely be the single largest draw, do not stop there. A few checks on the accessory circuits doesn't take much time.

 

Subscribing. Nothing to really add to what has already been said.
Need to see 14v at the batteries, engine running with the battery light off on the dash. Any deviation from that, there's a problem.
Sometimes finding the source of the parasitic draw can be very taxing with your patience. Relays sometimes are programmed to stay on. The dome light is a good example. When you shut the door, it stays on for a minute as a convenience for the passengers. So you have to recognize that and work with the truck's design as you are looking for the drain.

 

Im not sure a stock alternator would be at 14v at idle. Driving for sure, but i d9nt think my stocker ever saw 14 at idle. Usually around 13.5 to just under 14.

When it failed, it wouldnt even make ot to 13v while driving. Really showed itself with my now short commute

 

one last time:

a Clamp On Ammeter, is by far, the BEST tool to use to trace Parasitic Draw.

a MultiMeter checking for voltages is a PITA and requires unhooking things, and pulling fuses.

with the clamp on ammeters, you just start at the battery , and Follow the DRAW...

as Diesels have two batteries, you have to test both batteries first, to determine which one is providing the heavy Parasitic Draw.

for me on one occasion, that was the Alternator with the Key OFF.
( it was replaced with the MechMan )

solved the problem in one test.

 

My '02 was doing the same sort of thing. Discovered the alternator to battery cable was shorting out on the frame, the insulation had worn off the cable and it would intermittently ground itself and stop charging from happening. I had to splice a new cable in and I zip tied it so it couldn't ever rub again.
​​​​​YMMV.

 

Is it possible the engine dying is unrelated to the batteries discharging?

My first thought on the stall was the fuel bowl heater. Maybe disconnect it, check your fuses, and go from there.

 

I fixed the issue a few days after last posting. Just sharing the update.
I took out both batteries and charged them fully, cleaned corrosion off my connectors and got a brand new alternator. It seems the alternator was weak and not keeping my batteries charged