Low voltage issue 84 K10

[joshzgmchevy]

Hil..i have an 84 k10 Silverado. Dim headlights very slow power windows. Cranking drags like low battery occasionally. Alternator and battery check good. Could anyone tell me anything i could look into as far as troubleshooting further. thanks

 

[Bextreme04]

Take off all of the grounds, clean them(preferably by sanding the area and the ground wire with sandpaper), and then reinstall them with some kind of corrosion inhibitor. Add a large(4AWG or larger) ground wire from the alternator bracket to the frame and from the frame to the battery. Make sure the ground strap from the cab to the back of the passenger side cylinder head is present and both sides of the connection are clean.

 

[Rickf]

Check both battery cables and connections at each end. The cables could have hidden corrosion.

 

[Bextreme04]

Major grounds are located on the back of the passenger side cylinder head, both sides of core support, on top of the parking brake pedal bracket, and behind the passenger side brake light.

 

[Bextreme04]

Check both battery cables and connections at each end. The cables could have hidden corrosion.

This too. If you see any bubbling or bulging of the cable under the wire jacket, just replace the entire wire.

 

[joshzgmchevy]

wow so glad i found this forum you guys are fast and awesome..

 

[SirRobyn0]

Yea, these guys have hit it. Start with grounds, What I do is after cleaning up the grounds to bare metal is to coat the contact services with dielectric grease. If your not familiar with it, it's a special grease for electrical connections.

After that, you did not say what you did for an alternator test, but lots of guys will do a voltage check with a multi-meter, and sometimes a weak alternator will look ok on a test like that. So if you still have issues after repairing the grounds you might want to have the amp output tested on the alternator. I really think you'll find it in the grounds I just want to add that as food for thought.

 

[Memaloose]

You're right on the alt. A bad diode will still give 12-12.5 volts but won't put out 14-14.5

 

[Bextreme04]

For dielectric grease I recommend getting a tube of Dow Corning DC4. It's commonly used in aviation and is top tier stuff. I've seen old DC4 on 30 year old electrical connection in an aircraft still be in perfect shape. You can order a tube on amazon for pretty cheap. Its good for spark plug wires and light bulb sockets to keep out water also.

 

[SirRobyn0]

For dielectric grease I recommend getting a tube of Dow Corning DC4. It's commonly used in aviation and is top tier stuff. I've seen old DC4 on 30 year old electrical connection in an aircraft still be in perfect shape. You can order a tube on amazon for pretty cheap. Its good for spark plug wires and light bulb sockets to keep out water also.

Thanks for that tip. I'm pretty anal where it comes to how electrical stuff is put together and I just use run of the mill dielectric grease but will look into that stuff. Thanks.

 

[75gmck25]

My original ‘75 10si seemed to work okay, but lights got dim when also running heater blower, etc. Finally installed a cheap voltmeter and found that voltage dropped as low as 10.5 when everything was running at the same time. Replaced the alternator with a 94 amp 12si and it’s worked great ever since.

 

[Bextreme04]

My original ‘75 10si seemed to work okay, but lights got dim when also running heater blower, etc. Finally installed a cheap voltmeter and found that voltage dropped as low as 10.5 when everything was running at the same time. Replaced the alternator with a 94 amp 12si and it’s worked great ever since.

I did the same thing on mine. I used to have charging issues all the time and it couldn't keep the voltage up with just the headlights on. I decided to upgrade the alternator when I added the electric radiator fans, so I also ended up going with the 94 amp 12SI, since it is a direct replacement. I also removed the normal charge cable to the firewall stud and replaced it with a direct 8AWG wire with fusible link that goes straight to the battery. Now it always stays charging at 13.7 or above even with the dual electric fans running at high speed at idle. The original 10si I removed ended up having 37amp stamped on it... which explains why it couldn't keep up with power draw.

 

[SirRobyn0]

I'm sure you both already know this, but for anyone that reads this and doesn't, even a healthy alternator will not put out full output at idle. Most will by the time you get to 1,200 RPM though. It is not uncommon for even a healthy 37amp alternator to discharge at idle with the headlights and heater fan running. I have a 94amp on my truck the PO installed, and it's been great save for the one down fall which is that if the battery is run very low and you fire it up, it'll be hard to keep the belt from squealing at first. And yes everything is in alignment and the belt is in good shape and tight. You need to look at the pully on remaned alternators too, I've see some with pretty bad groves worn in the pully painted and shipped. One of these days I'd like to change my crank pully to 4 grove and maybe my water pump pully so I could go to a dual belt on the alternator, but yes the higher output alternators are great for power production, you just got to be careful because under high demand it maybe more than a single belt can handle.

 

[Matt69olds]

The 105 amp CS I swapped onto my Olds will put out nearly all it’s rated output at idle. I did have to swap the serpentine belt pulley for a standard V belt. The belt doesn’t squeal even with the alternator loaded to max output.

I think the Cadillacs with the old school small blocks (before they went to the LT1 style engine) had 145 amp alternators that should fit a older truck pretty easy. Definitely upgrade the charge wire with that one!!

The 94 amp SI alternator is a direct swap. The CS series either requires an adapter plug or very minor wiring changes.