Alternator Capacitor M1008

[Abbylind]

Ive looked around and I cant finrd a difinative answer for my M1008. The alternator on the the drivers side is for 12v, the alternator on the passenger side is isolated and produces 24v (12+12) for the second battery. I have an "alternator whine" on my communications equipment mounted in my truck (noise varies with engine RPM) Im very versed on vehicle RF generated noise so I know its the alternator. When I examined the rear of both alternators I find 1 capacitor on the 24 volt alternator but none on the 12v (drivers side) My internet readings seem to show the capacitor on the 12v side but none on the 24v alternator. Could they have put it on the wrong side or are their 2 of them (1 per alternator)?

 

[Warthog]

Both are 12v alternators. According to the wiring diagrams, only the passenger alternator has the exterior capacitor. Most of the trucks I have seen are missing that capacitor.

Is your equipment 12v or 24v? The military radios are 24v so the capacitor was installed on the 24v passenger side.

You can install one on the driver side to see if it solves your issue.

 

[Abbylind]

My radio gear is 12v..makes sense they placed it on the 24v side for mil radios (duh!).
Sounds like I should build one of these..
http://www.worldwidedx.com/home-brew/31492-building-simple-alternator-whine-ignition-filter.html

 

[doghead]

I thought they all have a capacitor inside them.

I believe all the ones I have rebuilt have had one inside as well.

 

[Abbylind]

That might be the rectifier diode bridge. Could be bad too....might have to test that on the 12v side!

 

[doghead]

Shown here

 

[doghead]

The above pic is not from the -34P, but it is shown there as well. Part number, 1978146.

Google, 1978146 capacitor

 

[Abbylind]

Bueno! Thanks sir. Appears there may be an internal capacitor next to the bridge

 

[doghead]

Here is the actual page from the TM.

Of course, the next page has the GM/AC Delco part numbers.

 

[Abbylind]

Search Results of Available Items *Prices are Per Unit Page 1: 1-1 of 1 items [HR][/HR][h=2]1978146 - CAPACITOR[/h] GM PART # 1978146 CATEGORY: Eng Asm (shipped only to local UPS hub 4 pickup) PACK QTY: 1 CORE CHARGE: $0.00 List Price: $10.74 Price: $5.48 You Save: $5.26 (49%) DESCRIPTION: CAPACITOR

 

[Warthog]

Forgot the one inside. Dohhhhhh!!!!!!

 

[Abbylind]

Time to crack open an alternator doctor!

 

[Abbylind]

If anyone needs a little "Dummies guide to Alternators" this is a good primer....

http://www.chargerr.com/Alternators/ALT.HTM