[SRR]

I don't drive my truck very often so the batteries are a pain to maintain. I recently got a new set under warranty so I decided to go ahead and install manual disconnect switches on them. I did that yesterday. In the process, I noticed the truck itself has a charge of 0.15 volts on it. I checked it again this morning and it still has 0.13 volts.

Where does this voltage come from? I assume it must be related to the IOD that sucks the power out of my batteries in a few weeks. Is there some sort of rechargeable battery in the radio or computer?

 

[OkDually]

Thread relocated over to the 6.5L section for better views and responses to your issue

:thumb:

 

[SRR]

Thank you. This is where I wanted to post it but wasn't sure about appropriateness since my question really isn't about an engine.

 

[Tommygunner]

There are capacitors in the radio, PCM, and other electrical. They are like little batteries. They will hold a small charge and give it up slowly over time.

 

[cruzer747]

Are you measuring this with the batteries completely removed or with the disconnect installed and switched off?

I will take a guess and say that it could be from the larger capacitors in the radio?

If it really bothered you you could go about it a few different ways, easiest would be to hook up the dvm where you can see it and start pulling fuses until it disappears.

 

[DieselPro]

Radiator is acting as a battery. Antifreeze needs changing.

 

[Tommygunner]

Radiator is acting as a battery. Antifreeze needs changing.

Oh yeah...... I forgot about that. Acid builds up in the coolant and you have a battery. DP is right on. Time to change /flush the coolant.

 

[57diesel]

You could also be reading the corrosion between body and frame or something like that. A digital meter doesn't put much load on things so they will practically read the voltage just from the air. A potato likely has a more amps (and volts) in it than you are getting from your truck.

 

[SRR]

Wow, I'm glad I posted this question. I'm tending to go with the capacitor theory since the voltage continued to drop. I read it yesterday afternoon at 0.1 v and I'm testing with the batteries completely disconnected from the truck. I'll check the pH of the coolant and will see if I can read any charge from the coolant itself. I'm having a hard time wrapping my head around how a radiator acting as a battery could put current into the electrical system of the truck, like at the cigarette lighter. With quite a few years on the coolant but only a few thousand miles, it's probably due to be changed anyway. pH should tell me something about that. I'll check my meter on a potato. I think there's one still in pretty good shape out on the compost pile and maybe one still in the house. We do have some good sweet potatoes. Thanks y'all!

 

[SRR]

There wasn't any need to check the pH of my coolant. It's carrying 0.25 volts. I will check the pH but only to satisfy my curiosity and will do it on a much nicer weather day.


The electric system itself went down to 0.06 volts.

 

[DieselPro]

Dang, I'm good! You might find a coolant temp sensor back feeding the current to the wires. It might be bad as well even though it works.

 

[Caldiesel1]

While I love the potatoes and antifreeze theory, I believe you should be looking at grounds. Since we don't know the type of instrument you are using I'd say start with the basics, grounds, sensors then funny green men. I believe you will find your answer somewhere there. Something acting as a capacitor will only hold a charge until propery grounded. The fluid alone will ground the radiator, and shouldn't give off anything. Capacitors in radio equipment discharge rather rapidly unless your running amps etc. Look for a grounding issue, or an instrument fault. Good luck! And keep us posted.

 

[Caldiesel1]

Also ya might want to check the battery disconnect, they are notorious for leakage.

 

[DieselPro]

The fluid alone will ground the radiator, and shouldn't give off anything.

To test the voltage coming from the coolant place one lead from a digital voltmeter in the coolant and one lead on a good ground.

Now try this for grins and giggles. Disconnect the batteries and temporarily ground the two terminals together to effectively ground out the capacitors or whatever you think may be back feeding current. Connect voltmeter leads between the +- cables. Now the system should read zero. Now here is the believe it or not section. > If voltage comes back up disconnect a temp sensor (there are two) Does the stray voltage go away? Sometimes it goes into the wiring through a temp sensor. Should you change the sensor> Maybe.

Some of this info is pure speculation and some of it dead on. Believe it or not!

Most of my stuff comes from out of the box so you may have to do these tests to get to the bottom of it.

Keep in mind if your coolant is carrying voltage that some form of electrolysis is taking place and can't be good for your vehicle.

 

[DieselPro]

Check coolant voltage with engine running to, shouldn't change but you can figure that out if it does.

Personally I think anything over .25 volts needs to be checked into... .4 volts is considered excessive.

www.familyhandyman.com/automotive/car-maintenance/coolant-testing-with-a-multimeter/

 

[SRR]

Dang, I'm good! You might find a coolant temp sensor back feeding the current to the wires. It might be bad as well even though it works.

You nailed it. I'm sure the radiator is making voltage and coolant is charged. I have the plastic coolant tank on the firewall. I insert a threaded rod into the coolant and check with a multimeter. With the positive probe on the rod and the negative to ground, it reads -0.025 volts. That seems bassackwards to me but that's how it is. Put the negative probe to the rod in the coolant and the positive probe to ground and it reads as positive voltage.

The positive leads to the batteries are completely disconnected. Now the charge in the truck electrical system is down to 0.03 volts identically stated by two digital multimeters.

I did change the coolant sensor a few years ago with a NAPA part. That doesn't mean it isn't bad again. I will definitely be changing the coolant soon. I siphoned some out a year or so ago to see how it looked and I added a bottle of Wixcool that I had laying around for a while. Not sure why I even wanted to do that since it was a leftover from my old Ford 7.3 IDI. I called Wix and they said it was cool to do. The coolant did look good but I didn't check the pH.

 

[Caldiesel1]

Snore.......we went from 10ths of volts to 100ths of volts. I'm not sure what your after here? Got an aluminum radiator? You have electrolysis, got a copper core radiator? You have electrolysis. Not to mention heater cores and hard lines. If you're worried about battery discharge it would take 3 years to discharge a 800 amp hr battery.

 

[SRR]

If this discussion is boring to you, you are cordially invited to quit reading it at any time.

 

[Caldiesel1]

SRR. I receive these highlighted posts from the website. I read them to further my knowledge in doing so, I ask questions and give my opinion. I ask the question of what's the end goal to the post because I want to understand the objective, the goal of the final outcome. This is what I've learned so far, it's an older truck, it has an electrolysis issue. You suggested sending units which I believe has merit but my friend DR Vasilio, who is a retired GM engineer says it ain't so. Dr V says to check some of the sensors you have replaced and you'll be surprised. At the end of the day I want to absorb the final outcome to this post, it also made me look at investigating my fleet of vehicles and equipment. I haven't been able to get even close to .03, but I'm still in the process of checking all the water cooled members of my fleet. Since you are not the original poster I'm not sure why you've responded. I know it's politically popular to attack instead of answer the question but you are not in a position to answer the puzzle. It seems to me that you have never gone through a critique, peer review or debriefing, and if you have you forgot the nature to the quest for understanding and knowledge.

 

[DieselPro]

I had a temp sensors that had opened up on the inside and the coolant was being subjected to 12 volts.

Been so long ago I can't give you any specifics but it is possible.

At the time I couldn't keep a heater core in the truck over a year before it started leaking.