Gen 1 and 2 stopped working need direction

[pgp29646]

86 M1009 - - A few years ago my Gen 2 went out so I moved the Gen 1 over and purchased a Civilian alternator to replace Gen 1. Recently Gen 1 light (civilian) came on. So, I used a multimeter to check voltage to the batteries and Gen 1 was pushing out 16v and Gen 2 14v. To me, that indicated the civilian alt was bad. I had it tested and it was bad. Since I still had the original Delco 27SI, I purchased a rebuild kit for the original 27Si and followed the steps to rebuild. Made sure I kept the washers in place to make it isolated ground. Put the rebuilt back in and no Gen 1 light and a Multi meter showed it wasn't charging but Gen 2 was still putting out 14 volts.
So, I dug deeper in the forum and tested the Gen 1 regulator plug - it tested out good 12.2 (Red), Brown - 0.0 key off, 12.2 key on. Still no Gen 1 light. Then I cleaned the firewall junction block. Hooked everything back up and NEITHER Gen 1 or Gen 2 lights are coming on and neither Gen is charging. Checked the regulator plug again, after a few starts and Gen 1 Red- 11.6, Brown 0.0 key off, 11.7 key on. Gen 2 Red 24 volts, Brown 0.0 key off and Key on. I checked and rechecked the Junction block and all the wires are on and tight that were on before the cleaning.

I'm thinking a fusible link popped but looking at the at the junction block - but I don't see any indication of a problem. Is there a way to check the fusible links if they "look" good?
What should the brown wire on Gen 2 read with the key on? Any ideas why it is not showing anything after cleaning the junction block?
Is there a specific type of rectifier for the rebuilds? The description of the specs of the rebuild kit was for Delco 27SI/200 Series IR/EF, 65 Amp/24 Volt, Bi-Directional, Neg. Grd., w/o pulley. I ask cause I tested the diode and rectifier and they both tested good, but don't know if there are different rectifiers for the 24v vs 12v alternators - did I receive the wrong rectifier?
The voltage gage is not working and is unplugged. I don't think that would impact the Gen 1/2 lights coming on. I'm stumped - why did the gen lights work before and now neither are working.

Thanks in advance for any insight/suggestions on next steps.

 

[Mullaney]

86 M1009 - - A few years ago my Gen 2 went out so I moved the Gen 1 over and purchased a Civilian alternator to replace Gen 1. Recently Gen 1 light (civilian) came on. So, I used a multimeter to check voltage to the batteries and Gen 1 was pushing out 16v and Gen 2 14v. To me, that indicated the civilian alt was bad. I had it tested and it was bad. Since I still had the original Delco 27SI, I purchased a rebuild kit for the original 27Si and followed the steps to rebuild. Made sure I kept the washers in place to make it isolated ground. Put the rebuilt back in and no Gen 1 light and a Multi meter showed it wasn't charging but Gen 2 was still putting out 14 volts.
So, I dug deeper in the forum and tested the Gen 1 regulator plug - it tested out good 12.2 (Red), Brown - 0.0 key off, 12.2 key on. Still no Gen 1 light. Then I cleaned the firewall junction block. Hooked everything back up and NEITHER Gen 1 or Gen 2 lights are coming on and neither Gen is charging. Checked the regulator plug again, after a few starts and Gen 1 Red- 11.6, Brown 0.0 key off, 11.7 key on. Gen 2 Red 24 volts, Brown 0.0 key off and Key on. I checked and rechecked the Junction block and all the wires are on and tight that were on before the cleaning.

I'm thinking a fusible link popped but looking at the at the junction block - but I don't see any indication of a problem. Is there a way to check the fusible links if they "look" good?
What should the brown wire on Gen 2 read with the key on? Any ideas why it is not showing anything after cleaning the junction block?
Is there a specific type of rectifier for the rebuilds? The description of the specs of the rebuild kit was for Delco 27SI/200 Series IR/EF, 65 Amp/24 Volt, Bi-Directional, Neg. Grd., w/o pulley. I ask cause I tested the diode and rectifier and they both tested good, but don't know if there are different rectifiers for the 24v vs 12v alternators - did I receive the wrong rectifier?
The voltage gage is not working and is unplugged. I don't think that would impact the Gen 1/2 lights coming on. I'm stumped - why did the gen lights work before and now neither are working.

Thanks in advance for any insight/suggestions on next steps.

.
The only way I know of to test the fusable links it with a continuity test.
Gotta have a meter or a lightbulb on a string of wire...

 

[Tow4]

86 M1009 - - A few years ago my Gen 2 went out so I moved the Gen 1 over and purchased a Civilian alternator to replace Gen 1. Recently Gen 1 light (civilian) came on. So, I used a multimeter to check voltage to the batteries and Gen 1 was pushing out 16v and Gen 2 14v. To me, that indicated the civilian alt was bad. I had it tested and it was bad. Since I still had the original Delco 27SI, I purchased a rebuild kit for the original 27Si and followed the steps to rebuild. Made sure I kept the washers in place to make it isolated ground. Put the rebuilt back in and no Gen 1 light and a Multi meter showed it wasn't charging but Gen 2 was still putting out 14 volts.
So, I dug deeper in the forum and tested the Gen 1 regulator plug - it tested out good 12.2 (Red), Brown - 0.0 key off, 12.2 key on. Still no Gen 1 light. Then I cleaned the firewall junction block. Hooked everything back up and NEITHER Gen 1 or Gen 2 lights are coming on and neither Gen is charging. Checked the regulator plug again, after a few starts and Gen 1 Red- 11.6, Brown 0.0 key off, 11.7 key on. Gen 2 Red 24 volts, Brown 0.0 key off and Key on. I checked and rechecked the Junction block and all the wires are on and tight that were on before the cleaning.

I'm thinking a fusible link popped but looking at the at the junction block - but I don't see any indication of a problem. Is there a way to check the fusible links if they "look" good?
What should the brown wire on Gen 2 read with the key on? Any ideas why it is not showing anything after cleaning the junction block?
Is there a specific type of rectifier for the rebuilds? The description of the specs of the rebuild kit was for Delco 27SI/200 Series IR/EF, 65 Amp/24 Volt, Bi-Directional, Neg. Grd., w/o pulley. I ask cause I tested the diode and rectifier and they both tested good, but don't know if there are different rectifiers for the 24v vs 12v alternators - did I receive the wrong rectifier?
The voltage gage is not working and is unplugged. I don't think that would impact the Gen 1/2 lights coming on. I'm stumped - why did the gen lights work before and now neither are working.

Thanks in advance for any insight/suggestions on next steps.

The rectifiers are the same for all 27si alternators. The only differences are the extra insulators and ground stud for the isolated ground.

When checking fusible links, I use a incandescent test light. You need something that pulls a little current. Fusible links can show continuity and still be bad.

If you haven't already done it, test the alternator on the vehicle. Click Here

 

[Barrman]

Check the fuseable links at the engine wiring harness block. The black diamond shaped thing with 2 studs above the glow plug relay. The BAT +, Terminal 2 of ALT 1 along with the BAT- of ALT 2 all go there and have fuseable links.

However, your truck side problems started after you took the firewall junction apart. I suggest you take it apart again and make sure no pins were bent over.

 

[pgp29646]

Check the fuseable links at the engine wiring harness block. The black diamond shaped thing with 2 studs above the glow plug relay. The BAT +, Terminal 2 of ALT 1 along with the BAT- of ALT 2 all go there and have fuseable links.

However, your truck side problems started after you took the firewall junction apart. I suggest you take it apart again and make sure no pins were bent over.

Many thanks for the feedback!

I said the junction block, but I ment the "black dimond shaped thing". That is what I cleaned on the truck side.
Today I tested the fusable links, all checked out.
On the Gen 2 regulator plugs, key off Red 24v, brown 0.0. Key on red 24 volts, brown 0.0. What should the Gen 2 exciter wire read with the key on?

 

[Barrman]

Try using the rear battery - as your ground source when checking ALT 2. It will knock your numbers down to the 12 volt range and eliminate some of the funky 12/24 issues. That makes it easier for me at least. But, I also use a Power Probe for this kind of checking.

The start of the ALT 2 exciter wire is the fuse for the 24 volt stuff at the very bottom of the fuse panel. Then it goes to the ALT 2 relay below where a radio would go if you had one. The starter relay and 24 volt gauge relay are all together with it. 12 volts from the ignition switch turns that relay on to let the 24 volts go to the ALT 2 light and then on to terminal 1 of ALT 2.

Since all of this worked until you started doing things. Check that fuse.

 

[pgp29646]

Thanks for all the help. Relays working and I did need to replace the 10 amp fuse, but still not working. Got the exciter plug to show 21v with the key on but Alt 2 just not working. I rebuilt that alt with a kit off ebay. Individual parts all check out good, all the isolation disks are in proper place, but that Alt is just not working. So I guess I'll look for a reman and bite the bullet to buy one.
Thanks again for all the advice!

 

[Barrman]

Swap ALT 1 and ALT 2. See if the no charge follows the alternator or stays with the passenger side before you spend more money.

 

[Tow4]

Thanks for all the help. Relays working and I did need to replace the 10 amp fuse, but still not working. Got the exciter plug to show 21v with the key on but Alt 2 just not working. I rebuilt that alt with a kit off ebay. Individual parts all check out good, all the isolation disks are in proper place, but that Alt is just not working. So I guess I'll look for a reman and bite the bullet to buy one.
Thanks again for all the advice!

Truck wiring is frequently the problem. Rebuilding the alternators or buying news ones, will not fix the truck wiring.

In post #3 above there is a link to a thread that tells you how to test the alternators on the truck. It does not use the truck wiring and will help you determine if the alternators are working. Did you follow the procedure in that thread and check to see if the alternators are working?

 

[pgp29646]

Tow4, thanks again fir the insight, yes- I did the test you outlined in post #3, and the alt2 showed 11v while the engine was running. My alt 1 is a civi, it's working correctly after replacing. Light golwes once the key is on and goes out after startup. Luckily NAPA has a lifetime warranty.
The alt 2 is what I rebuilt for this project. I have watched the rebuild videos at least 5 times, and reassembled Alt 2 - 4 times. Truck side wiring is testing good - (thanks Barrman). I must have assembled the alt 2 incorrectly (4x's) or received a part that is bad. I didnt think I would get the 11v output if it wasn't assembled correctly. The diode, rectifier, rotor all test good, but I can't test the regulator without a secondary power source from what the videos show. I would have thought the alt2 light would be lit up since it's not putting out the correct volts, but it never comes on at anytime. So at this point, I'm stuck. Any additional insight is appreciated!
I would switch alt 1 to alt 2 as suggested but I only have one isolated ground alt. I didn't think I could put a civilian alt on the passenger side.

 

[Tow4]

The 11 volts you are seeing is battery voltage. Just to be clear, are the reading the voltage from the B+ and B- terminal on the alternator under test?

If you are not sure, take it to Napa or Autozone and have them test it. Tell them it's isolated ground and make sure they hook the tester ground to the ground terminal on the back and not the case.

Here's my illustrated rebuild thread: Click Here

 

[pgp29646]

The 11 volts you are seeing is battery voltage. Just to be clear, are the reading the voltage from the B+ and B- terminal on the alternator under test?

If you are not sure, take it to Napa or Autozone and have them test it. Tell them it's isolated ground and make sure they hook the tester ground to the ground terminal on the back and not the case.

Here's my illustrated rebuild thread: Click Here

The voltage of the battery was 12.6 before the start of the testing. Using the regulator plug, testing the B+ (12.6, B- 0.0 - key off and 12.2 key on using the back battery as the neg). To perform the test you highlighted, I created 2 individual leads and put them onto the regulator 1 & 2 posts, alligator clipped a 3rd wire to the main B+ terminal and all wrapped all 3 around the + multimeter probe (accidently hit the case with the alligator clip and boy, that was a spark!). Once I started the truck, I grounded the - probe on the - rear battery post. Meter registered 10.8-11.2 v after starting. My intention is to take it to the local Napa and have it tested. I can get a reman from them if its bad since I apparently screwed up the rebuild. Thanks again for all your feedback!

 

[Mullaney]

The voltage of the battery was 12.6 before the start of the testing. Using the regulator plug, testing the B+ (12.6, B- 0.0 - key off and 12.2 key on using the back battery as the neg). To perform the test you highlighted, I created 2 individual leads and put them onto the regulator 1 & 2 posts, alligator clipped a 3rd wire to the main B+ terminal and all wrapped all 3 around the + multimeter probe (accidently hit the case with the alligator clip and boy, that was a spark!). Once I started the truck, I grounded the - probe on the - rear battery post. Meter registered 10.8-11.2 v after starting. My intention is to take it to the local Napa and have it tested. I can get a reman from them if its bad since I apparently screwed up the rebuild. Thanks again for all your feedback!

.
BE CAREFUL because once you hand over your original alternator - with grounding - you won't get it back!

 

[Tow4]

.
BE CAREFUL because once you hand over your original alternator - with grounding - you won't get it back!

Yes, I would just pay the core charge and keep my original. It's real easy to swap the parts out of the new one into the original rear case and then you have an isolated ground alternator again. Just pay attention to the insulators and if you change the bearing, support the case so you don't break it.

 

[pgp29646]

Anyone recommend a reliable source for the replacement parts?
Thanks again for all the advice and directions!

 

[pgp29646]

FYI, received the reman alt and everything is working as it should. I did keep the core to rebuild.