Alternator woes

[originalkwyjibo]

I would start with checking voltage.

[timsrv]

I would start with checking voltage.

I agree. If high (above 15 VDC) it would indicate an open in the battery sense circuit. If low (below 13 VDC) it would indicate an open diode inside the alternator.

[cpginkpt]

so basically just perform these tests (?) => https://www.wikihow.com/Check-an-Alternator

If it DOESN'T pass the voltage tests how can I be sure it is the alternator and not the wiring harness/fusible link/other crispy wiring issues that may be feeding the alternator?

I am also getting a whine from the engine compartment (hard to pinpoint) which combined with the Christmas lights point pretty firmly in the direction of a new alternator.

I just don't want to jump to that conclusion without ruling out other components like the wiring harness etc.

[timsrv]

We cannot tell you what direction to go until we know battery voltage. If you have a volt meter, get a reading from your battery while the van is running. For most accurate results, take the van on a 15 minute drive and get the volt reading while somebody is holding the vans throttle at ~ 2000 RPMs.

[cpginkpt]

Cold battery => 12.65
Start van, rev to 2k on tach => 14.68

15 minute drive
rev to 2K on tach => 14.88

turn on fan and AC, rpms drop from 1100 to 700 + engine shudder, volts drop to 13.2 and then slowly climb back up to 13.8 after 30 seconds. RPM still low with engine shudder.

Turn off fan and AC, volts return to 14.7 with no engine shudder and 1100 on tach

tune radio station to low AM frequency with static and rev engine. Upon rev the volume of static increases.

turn off engine => 13.01

[timsrv]

Although still below 15V, this is unusually high. I suspect an open in the battery sense circuit (would cause your alternator's internal regulator to go to max output). Staying below 15V could be due to a strong battery (ballast) or perhaps it's just the max output of your particular alternator. Most likely failure would be your FL 0.5G fusible link (little yellow plastic part in your battery compartment). It's talked about here in the Fusible Link Thread. Tim

Here is the next most problematic fusible link. The FL 0.5G fusible link is the yellow connector going to the positive battery post inside your battery box. It is rated at 0.5G (based on wire gauge, I'm guessing about 20A). This protects the alternator sense circuit that links the battery positive to the "S" terminal of the voltage regulator (built into your alternator). If this link is bad or disconnected, the end result is solid "Christmas lights" on your instrument panel and a "full field" condition in your alternator. Full field is when the regulator tells the alternator to go to maximum output all the time and can be dangerous. A short trip probably wouldn't cause any problems, but long term use could cause multiple electrical problems (due to over voltage) and worse case scenario could end with a thermal runaway condition occurring with your battery. Thermal runaways are scary and dangerous. The result is usually a pile of molten lead, plastic and battery acid all over the place. Thermal runaways have also been known to start fires, so don't push your luck with a bad or failing FL 0.5G link. Here is a what a typical 20 something year old one looks like:


Although slightly more protected than the main fusible link, this link is still in a harsh environment and after 20 years or so will probably need some attention. I haven't checked to see if these are still available through Toyota, but really didn't see the need for genuine Toyota here. If Toyota still has these, they will no doubt want more $$$ for them than what they are worth. I have found a good substitute for these through Summit Racing for $2.95. These PICO fuse holders are water tight and are rated at 30A. Since this is a "sense" circuit, there would normally not be any current here, so I am going to recommend using a 15A ATC fuse. Here are a couple of pictures:

[cpginkpt]

ah, good (or not)!....based on your first pic and what I see under the battery compartment I would say mine is snapped right off (below). I see a wire to the right and nothing connected to the fusable link so assume these should be connected.

So I will just order the part you recommended, cut out the old one and sotter the new one in place. Doesn't matter which wire goes where I assume (?)

[Landon]

Hey guys! This will be my first post. And I could really use some help.. So, essentially I pulled my alternator assuming it had a plug.. No plug.. Just individual wires.. Now I'm having a tough time being able to find out which wires go to which diodes.. Is there anything I should look out for or can I start interchanging these wire willy nilly until I find the right combo.. There is only 6 possibilities.. Thoughts?

[Flecker]

Hey guys! This will be my first post. And I could really use some help.. So, essentially I pulled my alternator assuming it had a plug.. No plug.. Just individual wires.. Now I'm having a tough time being able to find out which wires go to which diodes.. Is there anything I should look out for or can I start interchanging these wire willy nilly until I find the right combo.. There is only 6 possibilities.. Thoughts?

Don't do that... one second.

[Flecker]

Landon, use this diagram to sort it out...

[Flecker]

Heres a new harness as well if you want to repair yours...

https://www.amazon.com/XtremeAmazing.../dp/B06XCJSF51

[Landon]

Thanks!

[Landon]

Landon, use this diagram to sort it out...

So I folled what was on the diagram as best I could.. Still doesn't seem to be charging.. It doesn't get above 12.3 v.. This is so frustrating 😤