Dash switch current limit?
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Dash switch current limit?
Does anyone have any idea of the current limit you can put through the dash switches? I am mainly asking about the headlight switch...should i have the switch send signals to relays for the low and high beam, or can I run the lights straight off/through the switch?
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Re: Dash switch current limit?
I don't know what the current capacity of the switch is but strongly recommend using relays anyway. There's a few good reasons why OEM setups are done that way.
Read on if you want, but I do tend to get wordy...
- you can run your relay coil grounds to the switch and then a short wire to earth at the switch, so less wiring and less high current wiring to your dash
- filament globe lights are an inductive load at startup which means a current spike at turn on that causes arcing and reduced life of your switch contacts
- relays are easily replaced in the unlikely event they wear out, and 30A+ relays are cheap and will handle the 10 or 20A load of your lights without issue
- relays open and close their contacts more quickly than a switch reducing arcing at turn on/off
- the relay is ideally close to the main lights meaning shorter power runs and less voltage drop in the wiring giving you brighter lights (I always use much heavier power feeds than I need to for this reason also, wire is relatively cheap and if I upgrade lights the wiring is already good to go
- I work for a company that makes onboard battery chargers/isolators etc. and most customer issues are caused by shortcutting the installation, they try to cheap out on the simple stuff and it works when they test it but fails when they need it in the middle of nowhere
Cheers,
D
Read on if you want, but I do tend to get wordy...
- you can run your relay coil grounds to the switch and then a short wire to earth at the switch, so less wiring and less high current wiring to your dash
- filament globe lights are an inductive load at startup which means a current spike at turn on that causes arcing and reduced life of your switch contacts
- relays are easily replaced in the unlikely event they wear out, and 30A+ relays are cheap and will handle the 10 or 20A load of your lights without issue
- relays open and close their contacts more quickly than a switch reducing arcing at turn on/off
- the relay is ideally close to the main lights meaning shorter power runs and less voltage drop in the wiring giving you brighter lights (I always use much heavier power feeds than I need to for this reason also, wire is relatively cheap and if I upgrade lights the wiring is already good to go
- I work for a company that makes onboard battery chargers/isolators etc. and most customer issues are caused by shortcutting the installation, they try to cheap out on the simple stuff and it works when they test it but fails when they need it in the middle of nowhere
Cheers,
D
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'78 G60H Ute Cab - the cherry on top.
'80 G61H - the start of things to come.
'92 Pulsar Ti - my SR20 powered daily driver.
'01 Kessner 7x4 - the pack horse.
'07 Challenge Camper - home away from home.
'09 Prado - the family fourby and her daily driver.
'14 200EXC - a chainsaw with wheels.
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Re: Dash switch current limit?
all good info! what about the wiper and blower motor switches? the blower motor has that built in resistor that adjusts the fan speed, so I don't think I could even use a relay with that switch, unless i wanted to use a complicated multiple relay and resistor circuit, which seems like a waste. and the wiper switch should be good to go straight to the wiper motor?
all fused, of course...
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Re: Dash switch current limit?
Good question... 
If the original blower and wiper motor wiring was direct from the switches then they're rated to deal with the current, though we are talking about 50 year old switches - at least a bad contact is only inconvenient in these rather than spooky if the light switch fails on a back road...wipers could be fitted with relays for high and low settings if you can justify it - if your wipers are single speed only then 1 relay might be worthwhile doing (motors are inductive loads too), blower motor as you say much more messing about, you'd have to be a bit ocd to fit a multi-relay setup for that...but I might when the time comes
Actually, fwiw I'll probably ditch the resistor(s) and add a solid-state control box but that's my trade - if you're handy with a soldering iron you could probably google a simple PWM circuit with a mosfet switch...but I digress, sorry...like I said before I tend to get thinking and typing and...
Cheers,
D
If the original blower and wiper motor wiring was direct from the switches then they're rated to deal with the current, though we are talking about 50 year old switches - at least a bad contact is only inconvenient in these rather than spooky if the light switch fails on a back road...wipers could be fitted with relays for high and low settings if you can justify it - if your wipers are single speed only then 1 relay might be worthwhile doing (motors are inductive loads too), blower motor as you say much more messing about, you'd have to be a bit ocd to fit a multi-relay setup for that...but I might when the time comes
Actually, fwiw I'll probably ditch the resistor(s) and add a solid-state control box but that's my trade - if you're handy with a soldering iron you could probably google a simple PWM circuit with a mosfet switch...but I digress, sorry...like I said before I tend to get thinking and typing and...
Cheers,
D
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Re: Dash switch current limit?
The original switches don't go through any relay, so you're fine.
The original lights were 60 watts ea. on the high beam setting. I've been running 100 watts bulbs (off-road type
) for ages without a relay. I have the relays to modify the installation, but haven't done anything yet. This setup of 200 watts total will give approx. 15 amps running through the switch.
The original lights were 60 watts ea. on the high beam setting. I've been running 100 watts bulbs (off-road type
) for ages without a relay. I have the relays to modify the installation, but haven't done anything yet. This setup of 200 watts total will give approx. 15 amps running through the switch.Owner of the same Patrol since 1967