2001 blazer.

does anyone know what the voltage readings should be on the two wires in the plug to the alternator? both key off and key on.

So here is the situation:

I have been through four alternators in as many weeks. all of them were the cs130d. the guys down the parts store think it is either installer error or a different problem in the charging system. the tech from the manufacturer gave me about twenty minutes of his time but could not tell me anything i didnt already know.

i went in to get a rebuild kit for my year-old alternator as the bearings were loud. they didnt want to bother looking up a rebuild kit. so they cut me a deal on a reman "toughone" brand. this one charged 0. not one single volt. swapped that out under warranty.

the next one had a severe voltage drop under load. with the headlamps, blower motor and rear defroster were on, it was testing 11.5v on the dash, my multimeter, and the store's midtronics unit. the ability to use all three at the same time during a new england winter is a must. swapped that out under warranty.

and the alternator in there now, does not have a severe voltage drop under load. but it does not excite until i blip the throttle. sometimes twice. this happens only on a cold start. once it is warm, it self excites fine. again. during a snowy winter, this is unacceptable. i want to get into a warm car. not worry about a dead battery.

the 26 month-old battery was tested good by the midtronics device. my toaster oven load tested it "weak" but it started perfect right after the test. every time i have load tested a bad battery, it never started after.

it shows 12.4v before a cold start in the morning. should be 12.6 i know. but it starts great every time. the multimeter could have a margin of error. or the 15 degree temperature might drop it slightly.

all of the connections are clean. i took the die grinder and made sure contacts were bare metal.

gatorback belt is new. as are the tensioner and idler.

i thought there could be a problem with the SILP connector so i soldered a new one on. while there, i added a sense wire just to see if it was a sensing issue. twas not.

so now i just want to verify that my voltages on that connector are within spec.

i know that it is not very likely that i have gotten 3 faulty alternators in a row. these are supposedly checked 3 different times in the remanufacturing process. but all three have had different failures. it sounds like a bad ground issue. i checked them twice.

so if someone can check the voltage on the connector or advise me to check something else, i would appreciate the effort.

 

No such thing as a "deal" on a "Toughone" alternator. You experienced 3 different problems, all related to the alternator. Four bad ones in a row is not all that uncommon. Usually takes at least that many before you get a half way decent one


There are 2 red wires on the alternator. The large one on the rear stud must show battery voltage at all times. The small wire, in the connector, comes from the PCM and voltage will vary depending on load calculated by the PCM.


If you add a sense wire to the alternator stud, the regulator will keep voltage correct at the stud. The rear stud on the alternator in NOT a good choice when most of the accessories get their voltage from the fuse panel. There is far too much voltage drop from the stud to the fuse panel. For the sense wire, use a 14 gauge wire and attach it to the large red wire on the under hood fuse panel. That will force the alternator to regulate voltage at the fuse panel, rather than at the alternator output terminal. The alternator still needs the small red wire in the connector from the PCM, but the sense wire will control the regulator instead of the PCM.


Several members do the "big three" upgrade to the battery cables, which is a good idea, however, adding the sense wire to the fuse panel will help even more.

 

thank you again for your time captain.

the "deal" on the alternator was that they warrantied a year+ old alternator so i paid $0 out of pocket. i own and maintain a small fleet and the local store takes care of me.

the toughone brand is from motorcar parts of america. they rebuild alternators for advance, carquest, napa and i heard oreillys though i cannot confirm that. different brands but the same lack of quality.

tomorrow i will swap it out for one of those ad244 models. my thinking is that the production run of the cs130d models got a bad batch of diodes. the motorcar parts of america tech adviser did not discount this possibility. if that one fails to perform as expected, i will go to an old school alternator shop and have them build me one.

as for the wire readings, i was looking for key on and key off. engine off in both scenarios. so load is not considered. it is a way to confirm the pcm baseline is correct. i think.

you are correct with a remote sense wire being better. i did not need a sense wire. there was no flickering or other symptoms. i just tried it to rule it out. i did not think about connecting to the fuse panel like you advised. i connected to the feed side of the 175 amp fuse connector underneath the battery tray to get some voltage drop through the wire. with perfectly clean connections, it may have been a waste to do so. v=ir. the resistance of 3ft of 8awg wire is roughly .002 ohms. i consider that negligible.

the "big 3" upgrade is not something i would ever consider. i have no amplifiers or extra lighting. and i find that the wires are sufficient if kept clean. the battery to alternator fuse is rated at 175 amps. the stock alternator only puts out 105 amps at 3000rpms. about a third of that at idle. even if i put in the 145 amp ad244 alternator, the wires should be fine. and the difference of resistance between 8awg and 0awg wires over a 3ft span is .002 vs .0003. the improvements people see from the "big 3" is probably just attributable to cleaning the connections. big fat wires look cool, but they dont make a difference in stock or mildly modified systems.

my philosophy is to just keep the connections clean. and there can never be enough ground wires. when i wire my snowmobile or boat trailers, i run dedicated grounds to each light.

 

the new, rebuilt ad244 works perfectly. no weird issues at all now. fourth time is a charm. goes to show you how bad most auto parts store alternators are.

i will relocate the sense wire to where you advised.

feel free to delete this whole thread.

 

Nope, great information!