Last week I noticed how some of the lights and gauges on the instrument cluster "pulse" in time with the engine idle. It's starting to get a bit annoying and I thought I'd ask you guys if there was a fix for this anomaly.

 

The voltage regulator, (inside the alternator) is usually the culprit.

 

Thanks.

If that's the case, then a new alternator is going to have to wait a bit. I really need to replace the fuel pump, first.

 

You can service the regulator separately, you don't have to replace the entire alternator.

 

Oh, so this is the part I replace? I think I can do this...

 

Wait a minute...what do I do about this connection? Do I have to resolder the connection when I install the new regulator? Also, there was only one small wire coming off of the pigtail which attached to the regulator. Is this normal? There are provisions for (4) wires.

Oh, and I checked the graphite brushes and they still have about 5/8" left on them. Those should be good, right?

Update: Okay, I just purchased a BWD regulator and the socket is different from the socket on the existing voltage regulator. I can special order the right socket from Advance Auto but the pigtail contains (4) wires. Apparently, the voltage regulators are alternator specific?

 

Best to match up the regulator: compare the new one to your old one, terminal placement should the same. You shouldn't need to replace the harness connector. 1998 and older voltage regulator is not interchangeable with 1999 & newer. If I remember correctly you don't need to solder anything when you replace the voltage regulator, it bolts in. The rectifier bridge, (diode trio) is a different story, those you need to solder in.

 

Well, then I have a problem, Captain. The picture above is a shot of my current alternator. It looks like one of the ends is soldered to the rectifier bridge. In fact, the new regulator I bought this morning has a tab on it just like the old one which is soldered to the old rectifier. Also, the new regulator does have a different harness connection than what is on the old regulator. So, maybe the alternator is not a '98 model? I don't know. Advance Auto Parts and O'Rielly's have only one kind of regulator for a '98 model Blazer.

I guess I need to think about this a bit more

Update:

My alternator has DELCO REM stamped on the front of the housing.

 

The 1998 electrical harness connector has 4 holes for wires. One single red wire goes in the second hole from the top, the rest are vacant. If you unplug the connector, turn the ignition to the RUN position, the red wire should show battery voltage. Does this sound like what you have?

EDIT: It's always a possibility that the alternator was replaced with the wrong one.

 

Yes, that is exactly what I have on my truck. But, here's the problem. The new regulator has a new style socket which does not fit the old pigtail. The only alternator with my style pigtail is a Denso alternator and at $156.00, it's going to have to wait (for that price I could buy a 140 amp online somewhere else).

I wonder if anyone else has come across this problem?

I've attached some pictures for reference. They are labeled "new" and "old" to distinguish the two. I could probably order the new pigtail but I guess I would need to make sure I use the right wire when I splice the pigtail to the wiring harness.