So my brothers merc has an R-10 overdrive unit behind the 3 speed. It was working fine until one day, the fuse popped. Replacing the fuse only resulted in another one popping and no overdrive. We replaced the relay on the firewall and it fixed it. Couple months go by and pop! no more fuse. Some testing indicated that the relay was fine, but the kickdown switch would shock ya if you touch the case. So last night i replaced the kickdown. Took it out, 30 mph, clunk, whoohoo! fixed it. Shifted into 3rd od, then floored it to test the kickdown. Kickdown worked, but no more OD. Fuse has blown. Turn around and head home. So today i pulled out my Borg Warner "THE OVERDRIVE" book, and start testing things. Key on, ground the TH SW terminal on the relay, and click. Relay triggers the solenoid. Test this a couple times and POP. There goes the fuse. Swap a new one in, and after about 5 times triggering the OD solenoid, pop! Now im thinking its gotta be a dead short somewhere, but ill be damned if i know where! Anyone have any ideas?
Dead short would blow the fuse on the first try, sounds like the solenoid is starting to draw a little too many amps and goes over the fuse rating when it gets warm. Do you have another solenoid to switch out or you can test the amp draw.
Think this was the same issue a local car was having late last year. Pulled solenoid and found it was full of oil. Different solenoid fixed it that evening but a trans seal was ordered. Haven't seen it since so I can't tell you if it lasted.
ill pull the solinoid tomorrow and see what the resistance is like. At $265 dollars through vanpelt, ill call around to see what i can find.
Cheaper to find a good used trans (most solenoids are the same for ford, gm and other makes) or a place to get repair parts.
The solenoids have a fiber insulator disc inside that can disintegrate, especially if it gets soaked with oil. If the insulator disintegrates, it causes a short. I replaced one with a piece of sheet rubber and it did the trick.
Dynaflash 8, Im curious what the issue was and what you had to do to resolve it. I'm having the same issue now. Any help you could provide would be appreciated.
So this was a real pisser to diagnose. I almost (and I was really close by the way) decided to remove the stock type setup (relay & kickdown) and wire it up with a toggle switch. But I was determined not to let the blown fuses get the best of me. What made it difficult was the fact I was a 3 speed OD virgin. I had zero experience troubleshooting these trannies and while the web had plenty of wiring diagrams, there was little information on what causes the fuses to blow. To begin, I disconnected the governor and shorted the ground wire. I wanted to see if this would engage the solenoid...but not to be. It still blew the fuse. Next I removed the solenoid and tested it by connecting it to the battery direct. To my surprise, it worked fine. I expected it to fail, but it engaged perfectly every time I connected power to the 12v lead and grounded the case to the battery negative. With the only two variables left being the relay and the wiring harness...I replaced the wiring harness and tested again. Keep in mind, each test required dropping down off of the jack stands and taking a short drive...which would result in heating up the exhaust, engine, etc. As you might imagine, the test was consistent with the previous attempts...another fuse was blown with no progress made. Ugh! My last replacement item was the relay. So I researched the internet again and discovered how others had replaced the original relays with the newer Bosch style. This was encouraging so I made a trip to the auto supply stores and finally found a relay that would work. Unfortunately this didnt solve the problem either as another fuse was blown again. Scratching my head, and saying a few 4-letter words to vent...I decided to stop trying to outsmart the problem and just go back to logic. I figured the solenoid was the obvious point of failure so I decided to remove it and dissasemble it for a complete diagnosis. To my surprise, I discovered the two wires were actually shorting out when the leads were curved back and connected to the wiring harness. When the wires were straitened out (for testing purposes) they didnt touch...but when curved and connected to the harness...they would short and causing the fuse to be blown. Once I repaired the wires, all worked as designed. As all of us know, sometimes we make it harder than it is. And other times, Murphy has his own idea to keep us searching for new 4-letter words before we figure out how simple the resolution actually is. The OD now works as designed and it certainly tames the high-revving RPMs down to a peaceful cruise for my '56 F100.
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