Alternator doesnt like the rain, but still goes good on dry days.

I have had an issue with my alternator for a while now, I just cant "Break Down" and buy one if it works so well on dry days.

If it is raining and I have been in traffic for a while, the voltage drops to 11.8 or so with a good load on it. I have to start shutting things off if I want to bring the voltage back up. Most of the time I realize it when the wipers slow down.

I may have to look into a higher amp alt if I want to run in the rain with lights, fogs, fan and radio going all at once.

 

That is weird How many miles does it have

 

174,500

 

How old is your Battery ? If your battery is old or the terminals are corroded, your alternator will not keep up your charge. If the battery is good, then I would check your battery cables and see if they are good and can carry the current. Good Luck.

 

Just a wild thought, but have a look at the belt condition and tension. Maybe the belt is slipping when it gets wet????

Always good to check the condition of other items as previously mentioned. Battery, cables, connections. Perhaps you have an issue with corrosion or a connection (loose maybe) that when it gets wet actually is shorting/bleeding your power off to ground rather than charging the battery.

Do the simple/easy/cheap stuff first. Make sure everything is in good shape and adjusted to spec. Test components, clean everything, ensure good grounds, tighten everything to spec and inspect condition of components. If you don't have the tools or ability to test the components (no knock intended) then various auto part stores have testing equipment that can test the individual pieces and the system for you. Most do this for free.

Best of luck with it. Let us know what you find as may help someone else down the line with the same issue. Cheers

 

Belts were replaced at 90k, I should buy another set just cuz.
Battery is an Optima that is probably 4 years old now, terminals are clean.
I have removed the ring terminal from the alternator to clean and reinstall it.


As I said, I beat the alternator up with all the power I use.
It can handle it in dry weather, but doesnt like the rain.

I have a pair of fogs, a Kenwood with the 6.1" screen and a subwoofer, a streamlight charger, extra interior lights and a whole bunch of other stuff that drags it down. Then I get silly and run the lights fan and wipers and down it goes.

 

Sounds like the alternator is getting wet (they don't like that).
Is the 'splash guard' in place? The FSM refers to this as the 'engine undercover'.

 

What I want to know is, have you ever seen the rain??

 

Ah, makes more sense now. My guess is that when it rains you are putting more load on the system than when driving in the dry. Wipers, maybe lights at the same go, audio going, air/defrost on and as you said, in traffic so rpms are not kept up. The amp draw for the system is reaching a point that the alternator is not able to keep up.

If you have a high electrical demand then the first thing I'd do is the big three upgrade if you have not already. This will optimise the system and ensure that you are getting a good solid delivery of full potential of the electrical system. If you do this upgrade be sure to use the correct gauge wire to match the alternator output current etc. and fuse the connections at the battery.

If still a problem then next thing I'd do is total up your potential system draw with all your accessories, audio and what it takes to run the truck under full load.

My guess is that either your stock alternator is getting weak OR more than likely by the sound of it, with full system load it is not enough output to cope with the system.

I'd upgrade the alternator. I did the Cadillac alternator upgrade. Can be a great way to get the power needed on a budget. Simple to do really. Gave me a solid factory 140 amps of reliable power. I used to remember the specs, but seems like something like full 140 amps in at around 1000 rpm or some such. Anyway, real world useable power.

Some will cringe, but I went the pick and pull route. Pulled the alternator, had it tested and installed it. Total cost in the conversion was something like $45. That included the alternator, the plug for it (could have used the one from the pick and pull, but I bought new instead) and in my instance I needed a longer belt to fit it. Not all trucks will need the longer belt, but mine did. No biggie as another stock power steering belt is all you would need to buy to fit to the alternator. Makes it simple.

For me, I needed it for an audio system. I had a 60 amp alternator stock on my truck. I calculated total rms wattage, efficiency of the amps, system voltage and came up with a potential current draw of 113 amps at 14.3 volts! Of course that is not on music, but just a pure number. With music (due to its dynamic range nature) the actual potential draw number is more like 57 amps or so. Even at that you can see that my stock alternator would not be up to running the truck needs, recharging the battery AND running the audio system at full tilt. Something would have to give.

Anyway, with the upgrade (140 - 57 audio = 83 amps) I've got more than enough to comfortably run the truck with everything on and the system and still have room to spare.

Hope that helps.

Cheers