Starting getting P1636 and P0622 codes Wednesday night. Car drove fine Wednesday and Thursday, but Friday volts started to drop within 30 minutes, lost several electronics before the car finally died. Had to put in a new battery just to get the car home another 15 miles.

Started diagnosing today from reading other common threads. He is what I have learned so far.

Starter solenoid:
All connections are tight as far as I can tell. I have not taken off the longtubes yet, but was able to get my hand down there and nothing "felt" loose. I just replaced my starter 3 months ago, so all hardware is new down there. I went ahead and sprayed WD40 on it, but didn't change the fault.

Battery:
Obviously new battery reads 12 volts. Old battery sitting on the bench reads 11.6 volts, so obviously not a battery issue, it just needs to be charged since it was drained the other day. I used a jump box on it before I purchased the new battery.

Alternator:
Between POS battery post and alternator BATT post reads 0.60 volts
Ran jumper cable from POS battery post and alternator BATT post, problem did not go away (as I read Bill Curlee said).
Checked the pins on the plastic connector, (I'm assuming Pin D is the middle one, couldnt find any pictures stating which is which besides the schematic), and it read 12 volts.

As far as the fuseable link....I really not sure which wire on the solenoid that is, or what its suppose to look or feel like(from reading same post from Bill Curlee on an older thread).

I'm wondering if I do just need to replace the alternator?

 

What’s your charging voltage across the battery at 2000 RPM with a load on it ??...if you’re reading .6 voltage drop on positive side of charging circuit to me that’s a little high...I read .2 to .3 on mine...if I were you I would remove the B+ alternator cable take a small wire brush and clean the alternator stud and the terminal end...also pull off the battery positive cable and clean the area shown in the picture....spraying WD-40 isn’t going to do ANYTHING and looking is NOT good enough !!!...you have to remove the battery cable terminals at the solenoid and again clean with a wire brush...apply DeOxit if you are going to spray anything on it...did you check the NEGATIVE side of the charging circuit ????...that side is more important...read from alternator case to battery negative..,what do you read ???...mine reads about .02 v or .03 v or so...while you are down at the starter solenoid remove the negative battery cable and clean that as well...my charging voltage is usually 14.1 to 14.3 !!...these things have to be done before diagnosing your charging system !!

 

At 2000rpm, volts across the battery were 11.3

All connections are clean and tight, zero corrosion.

However, the wires to the solenoid are pretty dirty, and I really have no idea if one of them may be bad. How can I tell if the fueseable link...whichever wire that is...has gone bad?

 

There are 2 different sized fusible links at the solenoid. A fusible link looks like a piece of wire with rubber insulation spliced onto the end of the main wire. Flex them and pull them to check them. If the wire inside feels lumpy or hard or it can be stretched then it's bad.

As a minimum, I would take apart the solenoid connections, clean the terminals and put it back together.

 

That is not good at all!!! What does it read at the alternator's output stud?

 

Fusible links are either good or bad...just disconnect both ends of the cable and OHM it out !!

 

Problem ended up being the alternator. Ordered a re manufactured valeo unit and back to normal volts. been running good for past few days.