Does not charge

1988 ford econoline 150,
new battery, new alternator ; when sitting and idling recharges perfectly, when on the road depletes and does not recharge the battery. help please.

This is kind of backwards, more rpm’s should increase the charge rate. If this old van used an old fashioned V-belt the first thing I’d suspect is a slipping belt. The extra speed would increase centrifical forces on the belt and might cause it to slip. Simple fix, tighten the current belt, or replace it with a new one. The new one might have more rubber and get a better grip.

Check all the ground connections…Make SURE both the engine block and body are properly grounded to the negative battery post…

Thank you, I will mention that to my mechanic, I was hoping he has already checked but maybe not.

The idea that would make the most sense to me - though it may be a bit of a long shot is just that you need to replace the main cables. If they are old & corroding they are offering too much resistance. But it might appear to be fine with relatively low current flow & engine heat - i.e. at idle with the hood up. Closing the hood and driving pumps up current flow & engine heat, heats up the cables and increases resistance to the point that charging can’t be maintained.

Of course, now you’ll probably say that the cables were also replaced - but if they’re not its not a bad thing to do whether it helps or not.

Can you provide details about it is known the charging is fine at idle but not at elevated RPMs? (Voltage readings, etc, etc,)
Any charging problem should be easy to diagnose and your mechanic should be able to tell you why; not simply replace parts.

Assuming battery, cables, and alternator are good then some reasons for not charging could be:
Faulty field circuit. (The little red battery light on the dash does work doesn’t it?)
Faulty (usually burned) wire plug on the alternator, fusible link end, etc.)
Faulty belt tensioner.
In some cases the alternator pulley may have abnormal wear and the belt (assuming that is good here, right or wrong) may be slipping.
Bad voltage regulator. (Some are external)

Assuming your mechanical knowledge is very skimpy you might try turning the key on and making sure the dashboard battery lamp is illuminated.
With the key on and if the little light is actually lit then raise the hood and touch the alternator pulley with the tip of a small screwdriver, etc. You should feel a magnetic attraction at the pulley.

my mechanical knowledge is skimpy, I am gathering information to discuss with my mechanic since I lack the knowledge. the needle on the dashboard shows it is charging at all times almost on the center line, slightly past it. no lights come on to indicate there is a problem specifically related to the battery.
The engine light has been on for years and several mechanics and even Ford dealership worked on it and after spending so much money I gave up. the charging issue started several years after that. so I am not sure if there is a connection.

So you still need to clarify then. Your gauges give you no indication that you have any charging problem. So what does tell you that you have a charging problem? How is any of this being measured?

the only indication is that when I use the van on the road and stop after 1/2 hour or so and try to start it, the battery is depleted and I have to get it jumped. when I let it sit and idle it charges back up.
a couple of different mechanics have worked on it and they test it with their own testers and it shows it is charging but the problem still persists.

No answer or even wild guess can be provided without knowing what voltage is being produced. Surely the van has a voltmeter on the dash.

If the alternator is known good, if the dashboard battery light is operative, and if the alternator magentizes with the key in the RUN position then I’d consider a fault in the alternator to battery circuit; as in the fusible link I earlier referenced.

from what I understand it is slightly over 14, apparently that is good and in theory there should be no problem.

I don’t think that you have a battery problem. I think that you have a cable or terminal or similar kind of problem.

At one of those times when you stop & it won’t start has anyone ever put a meter on the battery to check its actual voltage? I’ll believe that the battery isn’t having its charge maintained one I know what the voltage reading is after a drive.

I have not tested that, the strong possibility seems to be wiring/cable/connections, as you mentioned

Let me throw out a possibility here. You state after driving it and the engine is at operating temperature that there is a problem starting the vehicle due to an apparently discharged battery.

Does this mean the starter motor cranks the engine over very slowly and is balky?
If the charging system is putting out 13-5-14 volts (normal) and that voltage is being provided to the battery itself then maybe what you have is a case of starter heat soak.

That is not uncommon with an aged starter and is somewhat more common with older domestic cars that have the starter motor mounted down low and the exhaust header is adjacent to the starter.
A dragging starter problem could be diagnosed by performing a starter current draw test.

As I was reading down this post, it struck me that no one suggested that the problem might be in the starter and not the charging system, unit I got to OK4450’s post.

I think that soon, jumping it will not start it hot, and it will begin to fail to start when cold also. This is a classic pattern of starter motor failure. Follow OK’s suggestion and get the starter load tested.

Have the battery load tested. I’ve seen some very strange defective faults in batteries lately, and you cannot discount the battery just because it is new.

Short story: I had a client with a fried alternator. He recently put in a new battery. No problem, I figured the old battery stressed out the alternator, and it let go shortly after. Put in new alternator, and sent him on his way. Calls me 2 hours later. Fried alternator. Figured a defect, got a replacement, put it in. Checked over everything, but instantly noticed the alternator was sounding distressed. Checked battery, 11.8v. But, was dragging nearly 80 amps through the charge line. Pulled the battery and took it to the parts store that sold it. They ran a diagnostic, and the battery passed the voltage/charge test, but failed the load test. They replaced the battery, and the alternator no longer sounded distressed. checked everything, and all was well. Talked to him 6 months later, and all was still well.

I tend to think Cigroller’s thought about a bad cable between the battery and the starter is right on the money. To prove it, checking the voltage across the lead while trying to start the engine when the trouble is occuring will tell the story. If more than a couple of volts of voltage drop across the lead is seen while trying to start the engine then the lead should be replaced. I suppose the main negative lead should be checked also.

This is the third battery I have put in, it can not be the battery and the 2nd alternator so it can not possibly be the alternator, the starter is fine, it has also been replaced, a few years ago but works just fine. it must be some connection, some cable seemingly insignificant. my mechanic said he has checked but he is going to check it again. I printed all the suggestions above and took it to him and he said he checked all of these possibilities, again he said he will check the wires and connections to see if he can find something he overlooked. I welcome your suggestions, hopefully one of these solutions will hit the mark.

Have your mechanic check the voltage at the alternator battery terminal to ground and compare it that at the voltage across the battery. Next put the positive lead of the DVM on the alternator positive terminal and the negative lead on the positive post of the battery. Let us know what the voltage drop is reading.

After you crank up the engine does the ammeter needle go half way or more up the charge side of the dial and then wiggle its way down to just above the rest position over the course of a few minutes? That is the sign of proper charging.

If there is a voltage drop of more than 1/2 volt DC from from the alternator to the battery, inspect the wiring and terminals to and from the ammeter. You might be able to feel the heat of a fault connection with the engine running. In the case I troubleshot, one terminal of the ammeter had gone ohmic discoloring the terminal and the wire connector. The problem was solved by replacing the ammeter gauge itself.

Hope this helps.