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voltage drop when raining


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cgwjtvette
New User

Feb 24, 2009, 5:50 PM

Post #1 of 9 (1896 views)
voltage drop when raining Sign In

I have a 1999 GMC Sierra & every time it rains or there is moisure present I get a voltage drop when truck is in gear @ idle to the point that the battery light goes on. Can any one help???


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Feb 24, 2009, 6:05 PM

Post #2 of 9 (1894 views)
Re: voltage drop when raining Sign In

First thing I'd check is that the belt is tight enough. If 5.7 it's self tensioned and they can be at the end of range for tensioner and perhaps even slight moisture allow belt to slip. If tight and has more range when tested then it could be idle is somehow too low and electrical load too high for alternator output with wipers, defroster(s) etc., all going if using them at that same time you notice this.

Might just need a new alternator too - test some stuff out first,

T



cgwjtvette
New User

Feb 24, 2009, 6:25 PM

Post #3 of 9 (1892 views)
Re: voltage drop when raining Sign In

Thanx. I was told it might be the belt, belt tensioner or both. Just didn't see how the moisure had any thing to do with that. I'm going to replace belt and see how it goes. Thanx again.


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Feb 24, 2009, 6:44 PM

Post #4 of 9 (1888 views)
Re: voltage drop when raining Sign In

I'm guessing of course based on moisture causing some slipping. If not and still related so directly to moisture I'd test spray with water in a mister/sprayer CAREFULLY when it's dry and NOT doing this with a mostly cool engine and see if one area reacts or causes this to happen and focus on that.

You'd need a helper to watch the battery light and mist things one at a time watching out NOT to get into fan or spray directly on anything hot especially electrical secondaries like coils, cap etc.

Check battery cable connections too. Those side post terminals can be lousy and unseen unless taken off, cleaned up if ok or replaced if needed. The alt will only put out so much and needs help at the peak loads or momentary spikes from the battery. They work together and need to and if only connected thru a hairline connection it could cause a "battery" light when loaded. I would think if that was so that starting would be a problem also not mentioned so far. Keep checking,

T



cgwjtvette
New User

Feb 25, 2009, 5:15 PM

Post #5 of 9 (1880 views)
Re: voltage drop when raining Sign In

Just replaced the belt today. It's supposed to rain here in Chicago tomarrow so we'll see how it goes.


cgwjtvette
New User

Feb 27, 2009, 4:26 PM

Post #6 of 9 (1871 views)
Re: voltage drop when raining Sign In

Thanx Tom-- That was the fix :)


way2old
Veteran / Moderator
way2old profile image

Feb 27, 2009, 5:11 PM

Post #7 of 9 (1870 views)
Re: voltage drop when raining Sign In

Way too go Tom---------



Being way2old is why I need help from younger minds


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Feb 28, 2009, 8:50 AM

Post #8 of 9 (1865 views)
Re: voltage drop when raining Sign In

Glad that's fixed!

W2O - I love that animation!

Here's some brew from Boston....


You can use that assortment as a chaser for shots of this stuff...



Wink

T



way2old
Veteran / Moderator
way2old profile image

Feb 28, 2009, 10:48 AM

Post #9 of 9 (1860 views)
Re: voltage drop when raining Sign In

Sam Adams aint bad. Drink it here at a local steak house.



Being way2old is why I need help from younger minds






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