Hey everyone, joined in hopes yall could help me sort out this quagmire.

Picked up a 1990 B150 from a friend, manufactured 4/90.

Died on the road while a friend was driving it. He pushed it into a lot, I went back with him to jump it. Couldn't get it jumped, so took the battery home, charged it, and went back for the van. Drove it home with the recharged battery. Voltage meter was reading near 12 with the recharged battery, and obviously slowly crept down.

Assumed it was the alternator because the batt held enough of a charge to drive the Van 15 miles home. Pulled the alternator, brought it to autozone... they tested it, said it was bad, and sold me a new one. They had a 120 amp in stock so I went with that because it was cheaper than the 90 amp I was replacing.

Put the new alternator in and batt still isn't charging. Here's what i've tested so far:

1.) Battery cables are a good circuit.
2.) Voltage on the dash meter confirmed by multimeter, runs under 12v.
3.) Voltage on the battery terminals drops when the car is running.
4.) Tested voltage coming off the alternator, grounding to chassis. Less than 12v.
5.) Tested both of the small points on the alternator, both have power.
6.) Jumped the two small points together in attempt to bypass ignition switch in case issue was there, no change in voltage.

So, assuming my new alternator is good , the problem must be elsewhere... wiring, VR, etc... so if the problem is elsewhere, what are the chances the old alternator went bad at the same time? Called autozone, had them double check the alternator. Another guy tested it and it passed 3 times. Old alternator was working fine, autozone just sucks.

Can't find a VR anywhere, assuming it's internal to the alternator. Autozone is insisting it's external but I can't find it. The one they sold me is listed as externally regulated on the website.

Stumped... 2 questions, first, what is going on with the charging system, and second, what should I do about autozone selling me an alternator I didn't need by mucking up the test of my original one, and sending me on a wild goose chase?

Thanks, tyler

 

I believe that van does in fact have an external voltage regulator. Look on the firewall in the engine compartment for a square-ish box. Typically it has three screws holding it to the firewall and a modular connector plugged into the front of the box. I think the connector is only two or three wires.

When this box goes bad all charging of the battery stops, and these are generally known to be a weak point in that era Dodge van.

Regarding the alternator -- most of us have been in that situation. I say call it all good and keep the new alternator installed the van so your charging system remains tip-top.

 

1990 the voltage regulator is internal to the engine computer.

Check the fusible link on the 6 awg cable between alternator and battery.

It is stuffed behind the brake booster.

A fusible link is a length of wiring with a different type of insulation. When blown they are designed to look burnt and stretch out. When 20 + years old they can fail with out appearing burnt or stretch out.

Also never ask a reman or new alternator to charge a dead battery. Fully charge it with a grid powered charger.

 

I did charge the battery with a grid powered charger... it was substantially charged after alternator swap. Just left it hooked up all day for a full trickle charge and behavior is the same. Sub 12v when running.

Autozone showed me a photo of a VR that was like a big flat box, looked like it was BIG like 4x6in. Didn't see anything like that under the hood. Attached a photo of a smaller box that connects to the B+ terminal, is that a VR?

I see all the wires snaked behind the booster, but they're all tied up... is the green wire in my photo the 6 awg wire you're talking about? Or is it the black one that runs to the alternator? The one on the green wire looks fine, as does everything else in the area.

 

Unless somebody before you added an external regulator because the stock one in the engine computer is fried, then you have no external voltage regulator.

The green wire is the fusible link, and appears to have been replaced in the past as stock it is black and slightly thicker than that.

You can add an external voltage regulator. On some years this lights the check engine light, on some years it does not.
If you have vehicle inspections, an illuminated check engine light is an instant fail.

http://alternatorparts.com/Dodge_Chr...tor_wiring.htm

 

to summarize:

i have a new alternator, good battery, and it appears the fusible link is replaced/still good.

on a 1990 b150 the regulator IS external, but contained in the ECU: http://alternatorparts.com/Dodge_Chr...tor_wiring.htm

However, ECU failures tend to manifest in overcharging rather than under, is that correct, and if so where do I look next?

Also, i know new alternators need to "charge up". How does a new alternator behave? Do i need to go cruise on the highway for a minute to get the thing charging, or should it get going on its own?

 

The alternator in your dodge should require nothing to charge when first replaced, but a fully charged battery. If asked to output a lot of amps when new, the brushes, which have not yet worn in to the curve of the commutator can glaze over and pass no current, or pop off the commutator and get stuck.

You can try fully fielding the alternator to test it, but it isa strong possibility the ECU's voltage regulator has quit

 

Well then, sorry for the bad advice. I thought the 1990 was the last year of the external regulator without an engine computer.

 

I think 87 or 88 was the last year of the external voltage regulator, despite what the parts books list as compatible.

Mine's an '89. I went through this issue in '04. I replaced a bad 90 amp alternator with a 130. It charged a dead battery for about 4 seconds before the fusible link blew.

I was unaware of this. I blamed the voltage regulator, since the new alternator tested good.

Every auto parts store tried to foist a new external regulator on me despite me showing them the haynes manual which said it was internal to the engine computer.

One tried to sell me a new computer. They would have succeeded if the one they got me allowed my engine to start, but my problem would have remained.

I went to an auto electrician asked them to wire up an external regulator as it was beyond my abilities and before I was aware of automotive forums. Guy took 5 minutes to pull out the old fusible link, replace it and sent me on my way for under 70$

That fusible link they installed is too thin, and too short. 14awg and 4 inches instead of 10awg and 9 inches. It heats up greatly when my batteries are depleted, and limits their recharging.


I added another thicker, fused path for (+)current as well as upgrading the grounds. M my digital ammeter has shown almost 110 amps from a cold fast spinning alternator with depleted batteries.

 

I installed a voltage regulator.

Used this diagram: http://alternatorparts.com/dodge_vol...ulator_kit.htm

This is also helpful for photos: https://dodgeforum.com/forum/2nd-gen...version-2.html

Details on dodge charging system: http://www.allpar.com/fix/codes/sensors/charging.html

also: http://ramchargercentral.com/electri...arging-system/


HOWEVER

Now i am reading between 15.1 and 15.4 volts at the battery terminals. This seems too high...

The alternator field coil is reading approx. 5v running, and 10v running with accessories, as it is supposed to according to the above links.

My fusible link looks good, not burnt or stretchy. What do you think of that voltage?