Starter Relay Wiring

A diagram for the terminals of the common starter relay on Harley's and also used in other applications also like brake lights etc. This relay can be used to control such things as driving/fog lights/larger headlights where a smaller control lead wire is desired to the switch.

For testing purposes, the relay can be jumped from terminals 30/51 to #87 to check for a bad relay. Doing this only verifies if the relay itself is the problem and does not verify the wiring to the solenoid or bar switch. Jumping it in this way will crank the engine with the ignition key on so make sure the bike is in neutral.

 

i am changing back to point ignition on my 77 flh. I do not have the stock starter relay, so i do not know how to wire the blue streak relay i have. The manual shows three terminals and conflicts with instructions from my newer relay. any help would be greatly appreciated :eam

 

I'm not familiar with the terminal designations on the blue streak relay but there is usually a diagram either with the unit when you buy it or printed on the case of the relay.

 

If you add two driving lights @ 55 watts each, which means about 9 amps, plus the headlight itself, another 4 amps on high beam, won't this trip the breaker if anything else is attached to that circuit? I'm trying to add two driving lights (constant) and sure like the idea of tapping into the relay.

 

If you have a DVOM (digital volt/ohm meter) you can find the terminals yourself. If there are 4 terminals, that means that 2 are the coil and 2 are the contacts (switch).

First find your coil. Using your meter set on ohms, check any 2 terminals. What you are looking for is a resistance reading of like 10-200 ohms (every relay is different, so coil resistance will differ. I'm taking a guess on the range, but it gives you the idea.) Once you find them, these are what engage the relay, so make a note. One comes from your start switch and the other goes to ground. What order doesn't really make a difference because it will work either way.

So the last two pins are for the starter. One pin from battery power and the other to the starter. If you want to check them with your meter, you won't get a reading (infinity ohms) because the relay is not energized (contacts are normally open). Once again, it shouldn't make a big difference which pin goes to which. It will work either way.

If you have 5 pins, you will still have 2 coil pins, but the last 3 are a supply pin, a normally open pin and a normally closed pin. With a meter you can easily find the normally closed pins because they'll read 0 ohms. Note which 2 pins they are. Now the hard part, you need to find which one is the supply pin. What you need to do is energize the relay by hooking up the 2 COIL pins to a 12v power source (I highly recommend a fused power source!!!) one pin to positive and one to negative. You will hear a "click". The relay is now energized. Grab your meter and check those same 3 pins. Once you find which 2 pins give you 0 ohms, you will notice that one pin was used when the relay was NOT energized and when it WAS energized. This is your source pin.

 

yes it does have a diagram but it only accounts for three wires not the four my manual says, it is just a round style with two larger posts and two smaller ones

the relay is not currenly wired correctly, so checking it may not be as accurate

 

The 2 small posts are your coil (1 to start switch and the other to ground)

The 2 large posts will control the starter (1 from the battery (fused?) and the other to the starter)

If it doesn't seem to work, check it manually to see if the relay is engaging by hooking up 12v positive (fused!!!) to 1 small post and ground to the other small post. You should hear and/or feel the relay engage. If that is working, while it's engaged, grab your meter and check for resistance across the 2 large posts. It should read 0 ohms.

If the relay is doing all those things but it still won't start, you'll need to look elsewhere like a bad starter/solenoid, loose or corroded battery cables. You my also want to check for 12v to the relay from the start switch.

 

according to my harley manual i am supposed to run one wire from the positive battery terminal together with one wire from the ignition switch to the #1 relay terminal. then one wire from starter solenoid to the #3 relay terminal. then one wire from the handlebar starter button to the #2 relay terminal, and one ground wire from relay to transmision stud.

according to the round style relay schematic: i am supposed to run the positive battery cable to the "b" terminal, the starter motor cable to the "m" terminal, the ignition switch lead to "s" terminal, the coil lead to "i" terminal (if applicable), then it states if original switch has only 3 terminals-B, M, & S, do not use "I" terminal.

these instructions do not seem to help me much, so any input would be useful

thank you

 

How about a pic of the diagram on the relay?

 

this is all i have from the starter relay

that does not look like it worked but i can explain easily, the two larger posts (B and S terminals) are across from one another and the two smaller posts (I and S terminals) are across from each other as well; creating a diamond shape pattern on the end of the round style relay.