Balthazarr
07-31-2007, 03:52 PM
As we all know, electrical problems can be extremely frustrating.
I decided to post the following regimen to help with this for people who
aren't electrically savvy or anyone else who needs a guide to testing.
87a is on those relays used with a changeover switch so disregard if it doesn't apply to the relay.
1 - You conduct 12 tests, looking for quantity & quality. The quantities
will be zero, very little, & infinity. The qualities will be good or bad.
2 - 85 & 86 should have some resistance. This is the electro magnet
circuit, & switches the other terminals.
3 - 30 & 87 is open without power through 85 & 86.
4 - 30 & 87 is closed with power through 85 & 86. You supply power to a
component when you close the original switch, e.g., the headlight switch.
5 - 30 & 87a is open with power through 85 & 86.
6 - 30 & 87a is closed without power through 85 & 86. You supply power to a
component when you open the original switch, e.g., usually to a 2nd thermo
fan, on a 2 stage system.
7 - There must be an open circuit between 85 or 86 & 30, 87 or 87a, or
between 87 & 87a. These terminals are not common parts of any circuit.
8 - All open & closed readings should be absolute, not close enough.
9 - All switching from open to closed on 30 & 87/87a should be immediate.
You will see the resitance reading flicker quickly from one to the other.
If you can read a resistance value for more than instant, the relay is
hanging up. If the relay hangs up with a DMM, it will not work when used in
a circuit.
It's not too difficult, & worth checking.
As for the additional beers during testing, sometimes it's better to walk
away from a frustrating situation, and approach it with a refreshed mind.
The final bit is that major electrical components use 12v. Starter motor,
fuel pump, bulbs, etc. EFI components use 5v. TPS, injectors, MAP sensor,
Crank Angle (cps) sensor, etc.
It's that simple. Now, grab another beer and feel confident with your new found knowledge of electricity.
I decided to post the following regimen to help with this for people who
aren't electrically savvy or anyone else who needs a guide to testing.
87a is on those relays used with a changeover switch so disregard if it doesn't apply to the relay.
1 - You conduct 12 tests, looking for quantity & quality. The quantities
will be zero, very little, & infinity. The qualities will be good or bad.
2 - 85 & 86 should have some resistance. This is the electro magnet
circuit, & switches the other terminals.
3 - 30 & 87 is open without power through 85 & 86.
4 - 30 & 87 is closed with power through 85 & 86. You supply power to a
component when you close the original switch, e.g., the headlight switch.
5 - 30 & 87a is open with power through 85 & 86.
6 - 30 & 87a is closed without power through 85 & 86. You supply power to a
component when you open the original switch, e.g., usually to a 2nd thermo
fan, on a 2 stage system.
7 - There must be an open circuit between 85 or 86 & 30, 87 or 87a, or
between 87 & 87a. These terminals are not common parts of any circuit.
8 - All open & closed readings should be absolute, not close enough.
9 - All switching from open to closed on 30 & 87/87a should be immediate.
You will see the resitance reading flicker quickly from one to the other.
If you can read a resistance value for more than instant, the relay is
hanging up. If the relay hangs up with a DMM, it will not work when used in
a circuit.
It's not too difficult, & worth checking.
As for the additional beers during testing, sometimes it's better to walk
away from a frustrating situation, and approach it with a refreshed mind.
The final bit is that major electrical components use 12v. Starter motor,
fuel pump, bulbs, etc. EFI components use 5v. TPS, injectors, MAP sensor,
Crank Angle (cps) sensor, etc.
It's that simple. Now, grab another beer and feel confident with your new found knowledge of electricity.