Alternator whine - but its not the usual suspects....

[Doubeleive]

Ok guys I did some more testing today, and I'm still stumped.

* I sprayed water on the alternator pulley and belt. It didnt make any difference to the noise, making me less suspicious of the belt.

* Then I connected jumper leads (both + and -) direct from the alternator to the battery. No difference. Note: I forgot to disconnect the alternator wire though...so this may be a false test.

View attachment 439687

* Then i plugged in my OBD2 scanner, and checked the BCM for charging data. It appears to be pulling about 60A:

View attachment 439688

I wanted to double check this with an amp clamp, but unfortunately I only have an AC one, so it didnt work.

* Then I checked for tensioner markings. I couldn't find anything definitive, so here are some pictures:
View attachment 439689 View attachment 439690


* Finally I Ohmed all of the cables and routes that power would take:

Positive Wires
+ Wire that goes from alternator to fusible link = 1.8ohm
+ One side of fusible link fuse to other side of fuse = 3.1ohm
+ Positive battery post to battery side of fusible link = 3.4ohm
+ Alternator post to positive battery post = 10.2ohm

Negative Wires
- Alternator body to chassis post on firewall = 7ohm
- Engine block to random bolt on body = 5ohm
- Battery terminal to engine block = 4ohm

BTW those are all high ohm's you should have pretty much 0 with few exceptions. 10.2 from alternator to battery is TERRIBLE that should be 0 no question

 

[Jimxms]

in that case are you 100% absolutely sure the whine is from the alternator? have you used a stethoscope to confirm? the most common thing to whine under the hood is the power steering pump followed by the tensioner and idler pulley with everything spinning you pretty much have to use a stethoscope to determine and single out the source of a noise.

All of the accessories, tensioners and idlers have been replaced. If i remove the cable from the alternator the noise instantly stops. I’ve also done the stethoscope ‘trick’ by using a long ratchet exertion bar to listen. It’s 100% the alt.

 

[Jimxms]

BTW those are all high ohm's you should have pretty much 0 with few exceptions. 10.2 from alternator to battery is TERRIBLE that should be 0 no question

I don’t think 0 would be remotely possible. Even touching my multimeter probes together has 0.1 resistance. The 0/1 awg copper wire I purchased has a resistance too.

To go from alternator to battery it’s got to go through the alu alternator housing, alternator mount, engine block, thin gauge oem wire and the battery clamp.

 

[Doubeleive]

I don’t think 0 would be remotely possible. Even touching my multimeter probes together has 0.1 resistance. The 0/1 awg copper wire I purchased has a resistance too.

To go from alternator to battery it’s got to go through the alu alternator housing, alternator mount, engine block, thin gauge oem wire and the battery clamp.

mine reads zero, and few things read much more the alternator bracket to battery negative reads .9
I have dual batteries battery-to battery across (under) the engine bay reads 0 and that cable runs from the battery to starter, then the 2nd cable runs under the engine and over to the 2nd battery.
I was having some charging issue's a few years ago, tested a whole bunch of things. engine compartment wiring should read very low, ideally 0
these vehicles are very finicky about voltage, poor grounds can cause a whole bunch of issue's
if he is really reading 10 ohms on the charge cable it's bad and needs to replaced, that's about a 3ft cable should be 0.0
personally if my alternator cable was reading 10 ohms I would throw it in the garbage can and buy a new one

 

[Jimxms]

mine reads zero, and few things read much more the alternator bracket to battery negative reads .9
I have dual batteries battery-to battery across (under) the engine bay reads 0 and that cable runs from the battery to starter, then the 2nd cable runs under the engine and over to the 2nd battery.
I was having some charging issue's a few years ago, tested a whole bunch of things. engine compartment wiring should read very low, ideally 0
these vehicles are very finicky about voltage, poor grounds can cause a whole bunch of issue's
if he is really reading 10 ohms on the charge cable it's bad and needs to replaced, that's about a 3ft cable should be 0.0
personally if my alternator cable was reading 10 ohms I would throw it in the garbage can and buy a new one

Its kinda a moot point anyway tbh, as even when I upgraded all of the wiring with 0/1AWG it's still making the noise

I'll try and find a diagram of all the main ground points on the car and clean those up, incase something else has corroded I guess :/

 

[Geotrash]

Its kinda a moot point anyway tbh, as even when I upgraded all of the wiring with 0/1AWG it's still making the noise

I'll try and find a diagram of all the main ground points on the car and clean those up, incase something else has corroded I guess :/

That’s the next step I would take, for sure.

 

[j91z28d1]

did you get a chance to do a voltage drop test? that might tell us something.

 

[Doubeleive]

did you get a chance to do a voltage drop test? that might tell us something.

that's one way to tell and you could test what the alternator is putting out at the main post and then check what it shows at the battery post, reading should be identical, if it's less the cable is no good
keep in mind the system is designed to put out a higher voltage for atleast the 1st 30 seconds after a start. It does that to boost the battery back up from the startup drop.

 

[j91z28d1]

that's one way to tell and you could test what the alternator is putting out at the main post and then check what it shows at the battery post, reading should be identical, if it's less the cable is no good
keep in mind the system is designed to put out a higher voltage for atleast the 1st 30 seconds after a start. It does that to boost the battery back up from the startup drop.

yeah, same same kinda, I have a alligator on one lead, so I like clipping it on the alt stud and then just touch the other to everything positive I can get to with a decent load on the same. then swap the clip to the alt case and do the same to all the neg and ground points I can easily get to.

anything more than say 0.2 ish I start looking for why but I've seen almost a half volt and and not been a problem if it's a long run thru an older harness