Moparts Tech Archive

Elec Topics

typical electrical amp loads

I decided to make a list of some typical electrical amp loads found on our older cars. This can be helpful if you are looking into alternator upgrades with a modified car. There are a few things I did not get specs on, but i can test them myself and add to this list. If anyone would like to add to this, please do so. Keep in mind, these are NOT fuse ratings, but actual load, and can vary some by manufacturers.

Line lock solenoid.......... 2A
12" electric fan.............6A
MSD 7al2.....................1A/1000 rpm
Holley black pump............4A
Meziere electric water pump..7A

Component
AMPS

Air Conditioner 13.50
Backup Lights 4.20
Clearance Lights - Front 1.18
Clearance Lights - Rear 1.62
Dome Light .97
Hazard Lights 8.40
Headlights 8.40
Heater -Defroster 10.00
Identification Lights - Front 1.77
Identification Lights - Rear 1.08
Instruments 1.00
Instrument Lights .96
Ignition 2.00
License Plate Light 1.18
Marker Lights- Front .54
Marker Lights- Rear .54
Parking Lights 1.26
Radio 2.00

Stop Lights 4.20
Tail Lights 1.81
Turn Signal 4.20
Windshield Wiper - Electric 4.00
Misc Add'l Load 4.00
Underhood Light 2.10
Map Light .97
Glove Box Light .24
Lighted Control Knobs & Ash Tray .34
Cargo Light 1.94

Another important component to consider is the starter. They normally draw about 50-150 amp and can jump as high as 250 amps under heavy load. So voltage drop is something to consider if your battery is in the trunk. If I remember right 5%-6% drop is OK for starters.

Moroso electric water pump drive (cog belt drive)
5.0 amps turning a Milodon high flow aluminum BB pump
5.8 amps with the 17" Summit flex fan on the wp too.

I'll add that the electric fan will take a bunch more amps to get going than it will at speed. That's why auto manufacturers use 30 amp relays instead of 10 amp fuses to power the fans.
The EFI fuel pumps are thee same way. idling at 7 psi, my T-Rex fuel pump hardly draws any amperage. When you run it on an EFI car and get into boost, the pump will draw much higher amperage to create the pressure needed to feed the system.

if this is any help, my SX performance fuel pump doing efi duty, draws
15amps @ 16vdc at 43.5 psi
12.5 amps @ 14 vdc at 43.5 psi
10 amps @ 12vdc at 43.5 psi
Dave

Fuse size will be 125% of running current load.

Tech Index