Help on Clutch Safety Switch
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Instructor
Joined: May 2003
Posts: 111
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From: Golden CO
Help on Clutch Safety Switch
I installed a brand new switch as Bubba had by-passed the old one. Now I can't get any reading on ohm meter when I press the clutch to the floor. It is a brand new switch. I disconnected the rod and held switch open and still no juice. Any suggestions??
:smash:
:smash:
Le Mans Master
Joined: Sep 2000
Posts: 9,078
Likes: 7
From: DFW TX
Cruise-In VII Veteran
St. Jude Donor '07
Re: Help on Clutch Safety Switch (criz51)
If you are putting an Ohm meter on the switch and opening it up. If it does not respond then it is bad or the meter is bad.
Drifting
Joined: Nov 2002
Posts: 1,665
Likes: 1
From: Ontario
Re: Help on Clutch Safety Switch (criz51)
- switch not pressed (with nothing connected to the switch), ohmeter should read open
- switch not pressed (with wires connected to the switch), ohmeter could read some resistance 'backwards' through the wires.
- switch pressed in - ohmeter should read a dead short
Don't rely on an ohmeter's readings if there is power applied to the circuit.
- If your ohmeter also measures voltage you should find that when the switch is pressed in you should have zero volts across the switch.
- switch not pressed (with wires connected to the switch), ohmeter could read some resistance 'backwards' through the wires.
- switch pressed in - ohmeter should read a dead short
Don't rely on an ohmeter's readings if there is power applied to the circuit.
- If your ohmeter also measures voltage you should find that when the switch is pressed in you should have zero volts across the switch.
Le Mans Master
Joined: Sep 2000
Posts: 9,078
Likes: 7
From: DFW TX
Cruise-In VII Veteran
St. Jude Donor '07
Re: Help on Clutch Safety Switch (Boofers)
I thought it would be the other way around, push switch and 12volts completes the circuit. How else would power get to the starter soleniod?
Drifting
Joined: Nov 2002
Posts: 1,665
Likes: 1
From: Ontario
Re: Help on Clutch Safety Switch (Budman78)
Yes you are correct that this switch does complete the circuit. Current flows through the switch to power to the solenoid. However, we want the solenoid to get as much voltage as possible, you don't want the switch to have a voltage drop across it.
Take Ohm's law: E (Voltage) = R (Resistance) * I (Current)
Ideally a switch when closed is a dead short, realistically it may have a resistance of 0.01 ohms or so, which is still very low.
The maximum current your clutch switch will see is upwards of 20 amps (when you start the car and power the solenoid).
If you apply Ohm's law to find the maximum voltage across the switch you get:
maximum voltage across the closed switch = (0.01 ohms)*(20 amps) = 0.2 volts
Not exactly zero but pretty close. So with the switch closed you should measure battery voltage between the solenoid terminal and ground, and nearly zero across the switch. Hope this helps :cheers:
Take Ohm's law: E (Voltage) = R (Resistance) * I (Current)
Ideally a switch when closed is a dead short, realistically it may have a resistance of 0.01 ohms or so, which is still very low.
The maximum current your clutch switch will see is upwards of 20 amps (when you start the car and power the solenoid).
If you apply Ohm's law to find the maximum voltage across the switch you get:
maximum voltage across the closed switch = (0.01 ohms)*(20 amps) = 0.2 volts
Not exactly zero but pretty close. So with the switch closed you should measure battery voltage between the solenoid terminal and ground, and nearly zero across the switch. Hope this helps :cheers:
