Sniper amperage requirements (1 Viewer)

[21NDone]

I have what I believe to be the original alternator from my '72 FJ40 and I plan to install a Sniper. The alternator was rebuilt and I'd really like to use it in the build. I've read conflicting information regarding the amperage output required for the Sniper. Some say the OE alternator with a ~ 35 amp output may not be sufficient. The truck is stock and there are no aftermarket parts installed.

Will the OE alternator be sufficient to properly power the Sniper?

 

[zerotreedelta]

No issues running the stock alternator on my '76 with my Sniper, and I also converted to the Hyperspark ignition as well.

 

[MOTOV8R]

The sniper has a 30 amp fuse (not sure what the actual draw is). The sniper provides the power to the fuel pump so this includes that power requirement as well. At night with running lights and headlights (assuming incandescent) it might tax your alternator.

 

[jhsmith]

Stock alternator worked for me with both a Sniper and a Hyperspark. Two years later I did upgrade the alternator to support more electronics and a winch.

 

[zerotreedelta]

The Walbro 392 pulls 9-10A to push 60psi, which should be pretty representative. I doubt the Sniper ECU and injector pull over 5A. Combined 15A would make sense under a 30a fuse, as you need headroom.

If you're worried, I'd just put the money toward LED headlights to reduce that draw (as it's really the only other big draw), rather than a bigger alternator, unless you're planning a winch or the like. You'd get other benefits like better lighting and reducing draw on the factory wiring harness and switch.

 

[charliemeyer007]

When my stock alternator dies, I'm going to a 120 Amp one wire unit. Back in the early 90, I slid into a snow/ice bank in my driveway. It was like 30 below, I spent hours getting free (turn the hubs in early if you think you might need them and its much easier to drive on to the chains before you are stuck). Anyway idling that whole time with both heaters on high, the high beams and interior light on, the big heavy duty battery was depleted instead of charged. Then the power went out for 2 weeks. I brought the battery in and set it next to the wood stove for half a day - I got the rig lit just barely using propane for starting fluid.

 

[21NDone]

No issues running the stock alternator on my '76 with my Sniper, and I also converted to the Hyperspark ignition as well.

Thanks for the response. I believe the alternator amperage of a ‘76 alternator is ~ 50 amps vs the ~30 amps in a ‘72.

The Walbro 392 pulls 9-10A to push 60psi, which should be pretty representative. I doubt the Sniper ECU and injector pull over 5A. Combined 15A would make sense under a 30a fuse, as you need headroom.

If you're worried, I'd just put the money toward LED headlights to reduce that draw (as it's really the only other big draw), rather than a bigger alternator, unless you're planning a winch or the like. You'd get other benefits like better lighting and reducing draw on the factory wiring harness and switch.

Thanks zerotreedelta - that information is consistent with what I’ve been able to dig up. I too feel the OE headlights are a big draw on the system. The only other draw I would have is the heater fan and the wipers, I’m sticking with the PTO winch.

 

[Jdc1]

We are running the 80 series alternator. In my experience with the Snipers, it doesn’t like a battery that isn’t fully charged but once running is fine off the stock alternator.

 

[21NDone]

When my stock alternator dies, I'm going to a 120 Amp one wire unit. Back in the early 90, I slid into a snow/ice bank in my driveway. It was like 30 below, I spent hours getting free (turn the hubs in early if you think you might need them and its much easier to drive on to the chains before you are stuck). Anyway idling that whole time with both heaters on high, the high beams and interior light on, the big heavy duty battery was depleted instead of charged. Then the power went out for 2 weeks. I brought the battery in and set it next to the wood stove for half a day - I got the rig lit just barely using propane for starting fluid.

You had me at 30 below, holy cow. Can’t make that $hi! Up. Thanks for the info.

 

[jhsmith]

You had me at 30 below, holy cow. Can’t make that $hi! Up. Thanks for the info.

Just a note on the 100 amp+ one wires from GM. The GM alternators use a 3/8 belt. My '75 FJ40 used a 17mm belt (which is just slightly different than a 5/8 belt). I initially used a 5/8 pulley on the GM 10SI alternator from a tractor parts supply house but had issues with slippage on the alternator shaft. Eventually put a GM 3/8 pulley on the lathe and cut it to continue to use the original 17mm belt.

Other than the pulley issue, the 10SI alternator upgrade has been good. Note, some mounting bracket modifications needed. I searched for a mounting kit online but never found one so had to fabricate one. Did anyone ever find a mounting kit?

 

[WildernessRimFab]

Will the OE alternator be sufficient to properly power the Sniper?

Maybe...seems to work for some but didn't work for me.

I ran a Sniper on my stock 72 alt (not rebuild) last year and I could see the battery voltage drop continuously at stoplights with the heater or LED headlights on.
I would say you can give it a try with the stock alt and see how it holds up. I switched to an fj80 alt from @ToyotaMatt and it works great.

Wiring up an FJ80 alt is 100% separate from your Sniper circuits so you wont gain any work efficiency by doing both sniper and alt at the same time.

 

[ryanwk628]

I believe the alternator amperage of a ‘76 alternator is ~ 50 amps vs the ~30 amps in a ‘72.

Where are you getting this? When I replaced the alternator on my 1970 with ACDelco Gold 334-1554 (same part number shows for '72) it was listed as 50 amps.

 

[21NDone]

Where are you getting this? When I replaced the alternator on my 1970 with ACDelco Gold 334-1554 (same part number shows for '72) it was listed as 50 amps.

Interesting, the information was given to me by a vendor on this site. Possible the information is not correct or I misunderstood them? This is the markings on my alternator:

 

[ryanwk628]

Interesting, the information was given to me by a vendor on this site. Possible the information is not correct or I misunderstood them? This is the markings on my alternator: View attachment 3523270

Interesting, looking up that PN it shows 40 amps, though some of the fork lift replacement parts show 45, and other pages show 55A alts as direct replacements. There is also 27020-60040 which lists as 69-75 FJ40s and 55s showing 55amps. Now I am curious and going to have to check which PN I took off.

 

[RLMS]

55 amp 60 alt minimum, also upgrade to LED headlights

 

[GA Architect]

FWIW - If you are going from an alternator with external regulator to one with an internal regulator, < click here > for how to deal with the voltage regulator plug/wiring.

With my Sniper, I'm running the 27020-61022-84 below, a 12V - 50A unit I had rebuilt.

But before that, I was running an OEM 27020-61012, 12V - 40A unit with the Sniper for a few years with no issues.

 

[21NDone]

FWIW - If you are going from an alternator with external regulator to one with an internal regulator, < click here > for how to deal with the voltage regulator plug/wiring.

With my Sniper, I'm running the 27020-61022-84 below, a 12V - 50A unit I had rebuilt.

View attachment 3523510

But before that, I was running an OEM 27020-61012, 12V - 40A unit with the Sniper for a few years with no issues.

Thanks for the info. What did you do with the amp meter in the cluster? Mine is -30/+30. Was yours a 50/50 meter?

 

[GA Architect]

Thanks for the info. What did you do with the amp meter in the cluster? Mine is -30/+30. Was yours a 50/50 meter?

-30 / 30+ ammeter is still in service in my gauge cluster. Also has the original main harness, but do run a set of LED headlights right now.

 

[ryanwk628]

Just checked the old parts boxes… The alternator that was on my 1970 (11/69) 40 was 27020-60032, shows as a 12V 40A alt, but -30/+30 on the gauge. Running the rebuilt AC Delco unit now which came up as a direct replacement when I ordered it

 

[21NDone]

-30 / 30+ ammeter is still in service in my gauge cluster. Also has the original main harness, but do run a set of LED headlights right now.

View attachment 3523583

All reassuring information, thanks! How did you address the temperature gauge for the cluster and the sniper? Because I’d like to keep the cluster temp gauge operational with the Snyper I’m thinking of adding an additional sensor in the head. Am i overthinking it?