I think my truck may be shorting out.....

battery shows over 12 volts, lights are dim, heater motor is slow, the starter randomly won't have enough poop to roll the engine over..

I tightened the ground on the block (loose), tightened the power on the starter (loose), and have checked all the other culprits, but I can't find anything newly wrong.....the electrical on this pickup has seen better days.....but it has always worked....

Any ideas as to where a guy could check next....I feel stupid for posting this, but am curious getting frustrated....

 

Have you had the alternator tested?

 

If you put a meter right across the battery terminals, and you're getting over 12 volts, but everything is running sluggish, then you have a high resistance somewhere in the main power circuit.

The most likely culprits are the battery cables. Check the terminals to make sure that they are clean and solidly connected to the battery. Look at the cables themselves. Are they corroded where they go into the terminals and lugs? Do they feel stiff and brittle? If they look real old, you should just replace them. Battery cables go bad with age. They develop corrosion under the insulation, around the strands. As the corrosion gets deeper, the cable builds more resistance, which makes it run hotter, which makes it corrode faster, etc.

Also check for good metal-to-metal connection where the lugs connect at the other end; at the starter solenoid for the positive cable, and at the chassis ground for the negative cable.

Too much resistance somewhere in the battery cable circuit means that everything electrical is going to get 10 volts instead of 12 volts. That makes a big difference.

And, like Mike said, check the alternator while you're there. With the voltmeter across the battery, you should be seeing 12.5-12.8 volts with the engine running 1500 rpm or so.

 

Try putting your meter somewhere else where you should be getting 12 volts and see what you get and start working back from there.

What do you get if you connect from say the battery + terminal to bare metal on the block? Should be VERY close to what you're getting at the battery. If not, double check your grounds. What about the alternator + terminal to the alternator case? Should be nearly identical to what you get at the battery. If it isn't then double check your battery positive and your grounds.

There are two ways you can do it, you can find a lower voltage and work backwards till you get the proper voltage that you are seeing at the battery. OR you can start at the battery voltage and start working forward until you end up with a lower voltage. Either way should have the same overall effect.

Also for what it's worth although a bad alternator or voltage regulator might keep your battery from charging properly, if your battery is fully charged they should have no affect on your starting. If you have good battery voltage (and it load tests good) but you are still getting sluggish starts, the alternator would be the last place I would look.

 

The battery is charging at 13.7 when the truck is running, so I did not check any farther than that. It seems to be somewhere on the output side of things. Why I initially thought bad ground.

what about the solenoid, could it be losing voltage before it sends power to the starter?

 

Load test the battery as NP suggested. Charging voltage is good.

 

Possibly. Easy way to find out. Disconnect the cable going from the starter to the solenoid. Put your meter on one side of it and make sure you're getting battery voltage. Then put your meter on the other side while somebody hits the starter and see what you get. That wouldn't explain your dim lights and sluggish fans though.

 

13.7 volts is perfect for charging.

I've never done this but it seems to me that you can do a "poor man's load test" by putting your voltmeter on the battery posts while someone else cranks the starter.

Now, I have no idea what the threshold would be for discarding the battery but one good way to find out would be to check a couple other vehicles the same way. But I'd guess that if your battery drops to 9 volts or less while cranking, you likely have a bad battery. Have you tried a new starter solenoid? Their contacts get burned and pitted and sometimes cause some wierd problems.

 

Seems like I have heard that your battery shouldn't fall below 9 or 10 volts. Suggest we find the root of the problem though before we start throwing parts at it. I agree that a flaky starter solenoid may cause some flaky problems but it absolutely will not affect his dim lights, sluggish fan, etc.

 

Yeah, I forgot about the dim lights issue; I was focused on the slow cranking thing, I guess. So I re-read the original post.

Probably not the battery but most definitely not "shorting out". High-resistance is your culprit. I'd be pulling all the big wires apart (the red and black ones between the battery, solenoid, starter, engine, frame and cab but focusing mostly on the black ones connecting all the grounds) and cleaning them up good. Also, they're relatively inexpensive to just replace but the point where they're connected must also be clean. In the old 6-volt world, the phrase, "clean, bright and tight" was the mantra but it applies in the 12-volt world just about as much.

Have you recently painted the engine, frame, firewall, or anything?

 

I load tested the battery last night, it tested fine. I tested the voltage of the battery, 12.4. I then had a friend turn it over so that I could check the voltage coming out of the solenoid, 2.2. Could the solenoid be malfunctioning? I had to jump it to get started so that I could head home from work.

last night I plugged it in to a battery tender and plugged in the heater. I checked the battery voltage this morning, it was over 14. It fired right up. so I checked the voltage again with it running. It was 13.52. I shut it down and checked the resistance of all the cables, all read 0.0. So I am not sure where to look now...

 

You measured the 2.2 volts on the starter side of the solenoid with the starter still connected? What do you get if you disconnect the starter and do the same test?

It could be that the solenoid is creating the large voltage drop, or it could be that the starter itself is kinda screwy too.

If you have the starter disconnected and you still manage 2.2 volts on the starter side of the solenoid, it is a safe bet that your solenoid is the problem. If you get full battery voltage, unfortunately you're not much further towards finding your problem.

Are there any shops around that can test your starter? BTW, I mean a real shop with real tests, such as a place that actually rebuilds them? I don't trust the parts store boys as far as I can throw them?

 

There is one shop in town, not sure if they can test it or not. I will have to ask. I will test the voltage with the starter un-hooked. I hope the starter is fine, not really hip on the idea of removing the headers....hoping it is the solenoid....It has had a tendency to stick during most of the last 10yrs of its life....prolly coming apart inside from the random beatings it gets....