1990 d150 not charging

Did you replace belt?Is it tight enough?Do you have fusible links?Check alternator wiring,may need replacing.Check battery,old alternator could of made it bad.Check ground battery cable,follow it's other end that is screwed into block.Also check positive cable to starter.Did you have the old alternator tested?Unlikely new alternator is bad.

the 1990 dodge Dakota came with two different charging and two different fuel delivered systems. If it had it a Bosch alternator the voltage regulator is built into it. Denso type with external voltage regulator with the voltage regulator is on the fire wall of the truck and may be the problem . Some part stores list the alternator for the for the external regulator don't list the Bosch internal regulator alternator at all for what ever the reason. And if they do the Bosch replacement will be higher in price (I found Nappa online store to have a better listing than some other parts listing) so back to your question replacing the CPU disconnect the Battery on the right side of truck just in frount of finder well you will see a black module with a air intake hose running to it this is the SUCB (single unit control board) remove the wiring plug by unscrewing the center screw and pull it free unscrew the 4 mounting screws and you are discounted this unit is sealed and will need to be replaced if replaced with one from a salvage yard make sure it is the same carbureted and fuel injection are different also 2 wheel drive and 4 wheel are different

that year 1986 alternator voltage regulator either external or internal follow alternator battery feed wire if you see battery feed wire going to black box mounted on fire wall you have external voltage regulator.if voltage regulator okay problem could be alternator fuse or fuse link could be faulty battery cables if cables over 20 years old but make sure alternator drive belt tension correct.

The first thing you need to do is stop wasting your money by replacing parts. Then get a volt-ohm meter and a test light to test the circuits between the battery, the alternator, the ignition switch, the starter relay and the voltage regulator. (a.k.a. Charging System Circuits)

To start, the "B+" or "BATT" terminal on the alternator (large black wire) MUST have a solid, direct connection to the battery. Check for the proper voltage here. Then, the red wire on the alternator at the "F2" terminal should be HOT at all times. If not, you probably still have a bad fuse link that you missed. The "F1" terminal on the alternator (Light Green wire) is known as your "FIELD" wire. It comes from the "IG" terminal at the voltage regulator. It should be hot any time the key is in the ON position. If not, your voltage regulator is not working or your ignition switch is not providing power to the regulator. Finally, The "F" terminal (Red wire) at the regulator should be hot any time the ignition switch is in the ON position. This actually gets it's power from the starter relay, which gets its power from the ignition switch.

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Almost all voltage regulators are part of the alternator now.

Your truck uses an external regulator. I would change that part. It is located Under hood, center, rear engine area, mounted on upper firewall

and looks like this:

https://s11.postimg.org/crrcun103/generator.jpg

Click on the link.
The diagram shows generator with internal voltage regulator and with external voltage regulator, at the moment, I don't know which one you have?
The bat terminal at the generator should be hot even with the key off, is it, use a test light. If no voltage either the fusible link is faulty or the wiring circuit to battery +. You can see fusible links in diagram.
Could be other issues, the generator probably needs excite voltage or it won't work. The excite voltage comes from charge indicator circuit. Does the charge lamp on the dash work?

just put a one wire alt. on it.or test each wire.

need the engine and whether its internal or external regulator and your fax or email