# Alternator size



## Mark13 (Dec 3, 2006)

I have a newer 105amp alternator and 2 800cca batteries and my lights still dim/blower fan slows down,etc when ever I move the plow up or angle it. I'm assuming my alternator just isn't up to the task of handing my radio, heat, lights, warning lights, and other electronics when plowing. What is a good size alternator to get that will keep up with all the power draw and still not be worked very hard? I'm thinking of getting a custom 250amp but is that overkill?


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## Mark13 (Dec 3, 2006)

With 2 800cca batteries should a 150 or 200amp alternator be plenty to power the truck/plow lights, radio(sub/amp), heat, back up lights mini lightbar, and 4 corner strobes all at lower rpm levels?


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## theplowmeister (Nov 14, 2006)

You don't need that big of an alternator. unless you are going to constantly run the pump. the pump draws150-300 amps when running, thats why the batteries to make up the difference of what the pump draws and the alternator can produce. when the pump is not running the alt charges up the batteries. The pump uses so much power it will dim lights, its OK. what is not OK is if over time (an hour or two) while plowing the battery voltage dose not recover. You probably haven't noticed but if you have your parking lights on and then switch on your headlights your dash lights will dim. It's OK. At home your house lights will dim when your compressor or fridge comes on its OK.


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## Mark13 (Dec 3, 2006)

Hmm, It gets pretty dang annoying though.

If I freshen up/rebuild my plow pump should it draw less power to work? I am unsure if it has ever been rebuilt but it is about 12 yrs old but this is my first season with the plow.


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## SnoFarmer (Oct 15, 2004)

Are you still using the stock wiring?
If so up grade.
The stock wiring on most trucks is inadequate to handle the load form plowing and the accessories that go along with it.

Then clean all your connections from the alt to your plow.


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## Mark13 (Dec 3, 2006)

SnoFarmer;468317 said:


> Are you still using the stock wiring?
> If so up grade.
> The stock wiring on most trucks is inadequate to handle the load form plowing and the accessories that go along with it.
> 
> Then clean all your connections from the alt to your plow.


I think it has like a 4 guage cable now should I go with 2 guage?
I have 4 guage linking my batteries together also.
The alternator and both batteries are new in the last 4 months.


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## grandview (Oct 9, 2005)

You could cut back on some of the lights!


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## theplowmeister (Nov 14, 2006)

Rebulding the pump motor may help. but you are still going to get a dimming of the other electrical stuff.


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## SnoFarmer (Oct 15, 2004)

Mark13;468320 said:


> I think it has like a 4 guage cable now should I go with 2 guage?
> I have 4 guage linking my batteries together also.
> The alternator and both batteries are new in the last 4 months.


Have you up graded your grounds to your body and to the engine?.
Ground the 2nd batt to your engine too.
( I used the same spot the alt is grounded at)

Some will double up on the +wire from the alt to the batt or fuse block.
Or install an larger cable, if you do this get a good cable with the ends already crimped on..

After I installed better grounds and wiring my lights no longer dimmed..

Ohms law, it takes one amp to push one volt through one ohm of resistance... larger or more wires= less resistance


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## B&B (Nov 4, 2006)

Mark13;468320 said:


> I think it has like a 4 Gage cable now should I go with 2 Gage?
> I have 4 Gage linking my batteries together also.
> The alternator and both batteries are new in the last 4 months.


Are the plow cables connected _directly to the battery posts _(including the ground) like they should be?

Did you upgrade the stock small gage charging wire from the alt? If not, get a 4 gage cable on it directly to the batteries.. make a real difference on the GM's. The stock charge wire is barely adequate for the job on a non plow equipped truck.

I'd do an amp test on the motor before just replacing it..

You can have the plow motor tested right on the truck if you take it to a local shop that has a starting/charging system analyzer. It's a very good way to test them, as your testing it in the actual scenario it's being used in.. Have them check the amp draw on the pump motor with the pump running in relief (full lift or angle and hold it there for a few seconds) Or you can use an amp clamp tester if you know someone that has one you could borrow.


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## doh (Sep 23, 2003)

Chebby makes a 105 AMP alt. @ lom RPM. it is what I run.


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## apik1 (Mar 25, 2007)

I have a 98 k2500 with dual 800 amp batteries I had the same problem. I have 4 gauage from the alt to the batteries. But with the heat, wipers, radio, light bar with 4 rotors, 2 set of flashers, and 12 strobes the light dimmed BAD, when I used the plow with the stock alt. I ordered a 200 amp alt, from Discount Battery for $ 189.00 plus shipping, and it came with a under size pully. The differance is amazing, The lights hardley dim at all with it. I wish I would have done it sooner.


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## B&B (Nov 4, 2006)

I like to see a 150 amp _minimum_ alt on a dedicated plow truck.

And in the case of a plow truck, whether it's batteries, cables or alt amps, more is better.


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## Mark13 (Dec 3, 2006)

grandview;468325 said:


> You could cut back on some of the lights!


Now what would the fun in that be?


SnoFarmer;468349 said:


> Have you up graded your grounds to your body and to the engine?.
> Ground the 2nd batt to your engine too.
> ( I used the same spot the alt is grounded at)
> 
> ...


My 2nd battery is grounded to one of the bolts that holds my ac pump on.
Iirc I have 4 guage between the batteries and my stock alt. wiring.


B&B;468350 said:


> Are the plow cables connected _directly to the battery posts _(including the ground) like they should be?
> 
> Did you upgrade the stock small gage charging wire from the alt? If not, get a 4 gage cable on it directly to the batteries.. make a real difference on the GM's. The stock charge wire is barely adequate for the job on a non plow equipped truck.
> 
> ...


My plow wiring is Not Directly connected to the battery.
I can do the amp test at school, the autoshop has all that neat stuff.



apik1;468441 said:


> I have a 98 k2500 with dual 800 amp batteries I had the same problem. I have 4 gauage from the alt to the batteries. But with the heat, wipers, radio, light bar with 4 rotors, 2 set of flashers, and 12 strobes the light dimmed BAD, when I used the plow with the stock alt. I ordered a 200 amp alt, from Discount Battery for $ 189.00 plus shipping, and it came with a under size pully. The differance is amazing, The lights hardley dim at all with it. I wish I would have done it sooner.


For a start:
-Redo plow wiring directly to the battery
-Upgrade alt charging wire
-Check grounds
-Anything else?

Are 4 guage cables connecting the 2 batterys fine or should I get 2 guage cable?

Then if all else fails get a bigger alternator?
And getting rid of some of the lights is not an option


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## bribrius (May 5, 2007)

i have the same alt i think. i have one battery which is the same the truck came with new and its eight years old. the lights dim.voltage gauge drops. but it comes up after. i ignore it. all i run for extras is a led rotator on the roof.
i have a cassette player which i never use and is the extent of the sound system.
a new alternator is on my list of things to get around to someday. chances are i will never get around to it though until the current alt dies, if it ever does. truck always starts first try. i dont care if the lights dim that much. not enough to go work on it anyway. maybe yours is worse because your running more things..


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## B&B (Nov 4, 2006)

Mark13;468537 said:


> Now what would the fun in that be?
> 
> My 2nd battery is grounded to one of the bolts that holds my ac pump on.


 It's good where it is BUT, run an additional 4 gage cable from the bolt on the compressor to the neg terminal on the 1st battery. This will tie BOTH the battery's, and the engine directly together and also take the load of the stock ground cable between the 1st batt and the engine (which right now is the only thing tying the 2 batt's together)



Mark13;468537 said:


> Are 4 Gage cables connecting the 2 batterys fine or should I get 2 guage cable?


 4 gage is fine as your cables aren't long enough to need anything bigger.


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## Mark13 (Dec 3, 2006)

Ok, I will try to redo my wiring stuff tomarrow and hopefully that fixes the problem for the most part.
Is the charging wire for the alternator just a normal cable with crimed ends(battery cable) that I can get at any automotive store?


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## B&B (Nov 4, 2006)

Mark13;468643 said:


> Is the charging wire for the alternator just a normal cable with crimed ends(battery cable) that I can get at any automotive store?


Even doing all this probably won't totally stop the light dimming issue.. It's just the nature of the beast. But it's worth it to try and diminish it as much as possible.

Yes you can just buy a 4 gage cable with the ends you need pre-made at most any store. You can leave the stock cable on and just add the extra cable to it.


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## Mark Witcher (Feb 21, 2004)

The only way to stop the lights from dimming on the truck is to separate the systems. Put the plow on its own battery by using an isolator between the truck battery and the plow battery.


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## SnoFarmer (Oct 15, 2004)

An Isolator is for a separate system like a camper.
It can charge a different kind and size of battery.

An isolator will not charge the second battery should the primary battery need any power from the ALT.
An isolator only charges the second battery after the primary battery is charged.

This still limits you to the cca of the one battery that is running the plow.
A plow may demand up to 100amps instantly.
A battery needs to complete a chemical response/reaction to this demand.
This takes time and can quickly drain a single battery that is not being charged by the isolator.

The reason you want to double up on battery's for plowing is the high amp draw and the need for the power to be instant.
Operating your plow with insufficient voltage can damage your electric motor also.

Also up grading your wiring will let the power flow Better and 
up grading to a larger ALT will also help meet the need for instant amps/power that a loaded down plow can demand.


jmo...


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## REAPER (Nov 23, 2004)

Dual alternator set-up with one dedicated to plow with the second battery.


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## apik1 (Mar 25, 2007)

Not to be rude but, a 200 amp alt $200, extra battery $ 85, 4 gauage wire and lugs from welding store $ 25. What is so hard to understand for some people? This will fix most problems and worries, unless the motor is shot on the pump drawing a million amps. Don't use an isolater or solenoid, they are both junk I learned this from experence.

If you are looking for a hi amp alt try 1-800-796-9394 and ask for Chris Gates or email him at [email protected] Mine came from there and it works great.


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## Mark Witcher (Feb 21, 2004)

A single battery and 125amp alt is enough. Adding a second battery and a 200 amp alt is not going to completely eliminate the lights from dimming . A correctly mounted isolator of the proper amp rating will when used with a good battery. 
And why is everyone getting so anal about a little dimming of their head lights? I dont even notice when plowing.


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## mnormington (Dec 18, 2007)

Mark Witcher;469348 said:


> And why is everyone getting so anal about a little dimming of their head lights? I dont even notice when plowing.


DITTO


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## apik1 (Mar 25, 2007)

Mark Witcher;469348 said:


> A single battery and 125amp alt is enough. Adding a second battery and a 200 amp alt is not going to completely eliminate the lights from dimming . A correctly mounted isolator of the proper amp rating will when used with a good battery.
> And why is everyone getting so anal about a little dimming of their head lights? I dont even notice when plowing.


Well it did in my truck, they will only dim a very little only it the truck at idle and I move the plow, but when the truck is moving just past idle they don't dim at all.


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## Mark13 (Dec 3, 2006)

I changed my plow wiring around some and added another wire off the alternator so hopefully it will help. By tomarrow morning I should know for sure. If they still dim quite a bit I guess a 150 or 200amp alternator may be my next purchase.


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## topdj (Oct 6, 2007)

Im running dual battery
with a 145amp no dimming that I can see


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## REAPER (Nov 23, 2004)

Mark13;469613 said:


> I changed my plow wiring around some and added another wire off the alternator so hopefully it will help. By tomarrow morning I should know for sure. If they still dim quite a bit I guess a 150 or 200amp alternator may be my next purchase.


Was this before or after you found the plow would not work?

I plow with headlights off btw.


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## Mark13 (Dec 3, 2006)

REAPER;469691 said:


> Was this before or after you found the plow would not work?
> 
> I plow with headlights off btw.


We changed the stuff before we realized the plow would not work. We undid all the new stuff and it still did not work. We think we have it fixed though, poor ground to the solenoid.
We now have all the new stuff hooked up and the solenoid grounded better and it worked.


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## REAPER (Nov 23, 2004)

Mark13;469855 said:


> We think we have it fixed though, poor ground to the solenoid.
> We now have all the new stuff hooked up and the solenoid grounded better and it worked.


I hope you got it fixed.

Looks like by you will be hit the hardest.


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## Mark13 (Dec 3, 2006)

REAPER;469857 said:


> Looks like by you will be hit the hardest.


Arn't we like 20 minutes apart at most?


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## REAPER (Nov 23, 2004)

Mark13;469862 said:


> Arn't we like 20 minutes apart at most?


If you are in Woodstock yes.

I was thinking you were in Marango.
They were suppose to get dumped on heavy.


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## Mark13 (Dec 3, 2006)

REAPER;470432 said:


> If you are in Woodstock yes.
> 
> I was thinking you were in Marango.
> They were suppose to get dumped on heavy.


I'm in Woodstock. How did plowing go?


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## REAPER (Nov 23, 2004)

Mark13;470519 said:


> I'm in Woodstock. How did plowing go?


12 hours out.

Timing was bad as far as traffic.

Left about 10A so I could be at post office in Highland Park to keep truck loading area wet and down to pavement..


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## svelasquez (Nov 28, 2007)

*Thank you...*

Thank you all for your replies to this. I'm sitting here taking notes feverishly on some of your feedback. I only recently purchased/installed my plow on my GMC and am now getting an education on some stuff I never knew or even heard of.

Thank you.


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## Detroitdan (Aug 15, 2005)

I had these problems even back in the old conventional hydraulic Fisher days, with no electrics on the plow. I tried a bigger battery, still dimmed with rotators, heat defrost and wipers going. Tried dual batteries with an isolator, was a bad idea, didn't work worth a dam and new stock alt didn't want to properly maintain. Could actually kill battery and stall the truck.
Then went to non-isolated dual 880s, with a PowerMaster hi output alternator. Much better, no more real problems but still dimmed lights under loads, batteries took a little while to recharge unless I was running the motor up. The hi amp alternators are just a little better winding and an underdrive pulley, you can make it yourself by swapping pulleys. Problem is they only charge at higher rpms, lower rpms they aren't putting out squat. This truck I have 2 big matched Diehards, new NAPA stock alternator, and never have any trouble. That isn't to say I don't get dimming when I work the plow, but like plowmeister said, it's OK. It recovers right away, even if I do an hours job, driving a few minutes to the next one gives it a chance to recover.


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## streetfrog (Dec 9, 2007)

I had to replace my alternator yesterday. (94 K1500 5.7L ) You will find that your options are going to be a 105 amp (oem) a 120 amp (hd) or possibly a 140 amp. that is pretty much for over the counter. If you want a 200 amp you will have to get it built from what I have seen.


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