Side-Terminal (Old-Style) Starter Relay (E9TZ-11450-B)
IF THE IMAGE IS TOO SMALL, click it.
The worst characteristic of this design is that the flat surfaces on the heads of the 2 main contact bolts have to be perfectly parallel for the washer to make good contact. But because the nuts are tightened in opposite directions, the flats are always misaligned, resulting in VERY small contact points between the bolts & washer. This commonly results in either 1) the bolt corners burning to the point that they don't make contact or power the starter; OR 2) the washer welding to the bolts, causing the starter to continue spinning whether the engine is running, or the key is removed. If the bolts had splines, it would help keep them from turning, but none do. The fact that the big copper washer can rotate (when it's not severely corroded) also helps by exposing clean copper to the bolts, but it doesn't clean the bolts or itself.
In the lower R, I've sanded the corrosion away, but it's not a practical way to keep the relay working when the later design is so superior, and inexpensive. So I recommend NEVER using this style relay for a starter, or any other high-current circuit. Use the new style with all studs parallel, opposite the mounting base, whenever possible.
To test a relay for the symptom of no cranking, bypass the relay by bridging the 2 large posts. If the starter doesn't work, diagnose the starter. If the starter works as it should, but doesn't work using the key, bridge from the Bplus post (the one with the LARGER cable from the battery positive) to the small (S) post. If the starter works, the relay is good and the fault is between the ignition switch & the relay (clutch switch or neutral switch). If not, the fault is at the relay. If the relay didn't click, either it's not grounded, or its coil is burned out. If it did click but the starter didn't engage, the relay's contacts are corroded as the top R pic shows.
To check for this withOUT disassembly, test cranking (relay triggered) voltage across the 2 large terminals. It should be under 1.5VDC. Anything higher indicates high resistance inside the relay.
To test a relay for the symptom of starter spinning constantly, disconnect all the small wires. If the starter continues spinning, the relay is welded. Rapping sharply on it may break it free, allowing the starter to stop.
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http://www.revbase.com/BBBMotor/Wd 
