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edward_davis Member 
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Can anyone give me an idea where to find the reverse light switch on the 4-speed gearbox? I've looked at the diagram in the manual but can't find any evidence of it. Also, I would appreciate any information on the best places to start looking for faults in the reverse-light circuit. Sorry if this is posted multiple times: my browser flaked out. Thanks |
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Mark Rosenbaum Member 
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For 4-speed cars, the switch is item #28 on the Gearbox Controls drawing. It's located far forward on the left side of the transmission top cover, and is rather hard to get to. Troubleshooting is pretty simple. Power from Fuse #1 runs to the Ignition Fused Junction under the dash, and thence to one of the switch contacts. The other switch contact connects directly to the sockets for the two backup lights. The switch should be closed when the gearshift lever is moved into reverse, and open otherwise. If the switch works fine when removed from the transmission, but not when installed, most often that's because the washer between the switch and the transmission top cover is the wrong thickness. Occasionally you'll find excessive wear either to the part in the shift linkage that activates the switch, or in the ball in the switch on which the linkage presses, or both -- for which the cure is a thinner washer under the switch. The attached drawing may help. Attachment: Bacjkup switch.jpg (Downloaded 217 times) |
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Ron Mau Member
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I found that the ground at the light wasn't quite good enough to ground the light so Iwould check there also. Use a short piece of wire and ground the lamp socket and see if that solves your problem. Ron Mau |
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dwalls1 Member
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My back up lights quit working. Connecting the two wires together at the switch the on the transmission lit the lights. I removed the switch and bench tested it and it seems to work fine. Reinstalled it less the spacer washer and still no lights. What next? Is it possible the switch is still the culprit? Can the switch button be extended, say with a glob of weld material. That would, of course, invite disaster if the glob broke off. Any responses very much appreciated. |
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Jensen Healey Super Moderator 
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Yes, you need to test the switch itself. |
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dwalls1 Member
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Thanks for the prompt reply. I did test the switch with a power source in series with a test light. Do I need to replace it with a new switch to get a definitive test? |
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Jensen Healey Super Moderator
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Sounds like it's time to check the nub on the linkage. |
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dwalls1 Member
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That looks like I'd have to pull the tranny as,"therein lies the nub" |
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Jensen Healey Super Moderator
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It is interesting that removing the washer didn't allow the switch to operate. How does the ball contact point on the switch look? Maybe you could use a piece of wire or a bolt to measure the switch seat to nub distance. Then compare with the male end of the switch body to make sure it's being engaged. It may be slop in the shifter isn't moving the nub into position. |
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dwalls1 Member
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It does seem strange that the nub would be the problem. The ball end looks good. I may play with it some more when I get a chance. It's pretty fiddly as I am working "blind" up in that tunnel, but I may probe that hole and see if I can feel any thing inside there. The switch could still be fooling me, so I will take it to work and blow compressed air in it, perhaps clean the contacts or something. |
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dwalls1 Member
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Tested the switch several more times today, with inconsistent results. Ordered a new switch and I am confident that that is the problem. |
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dwalls1 Member
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Installed the new switch with the spacer washer, lights work fine. I had retested both the old and new switches with the multi meter and got results that made me certain that the old switch was the problem. |
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JPJH Member
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I wanted to add a few comments having just done this. My backup lights were out and I spent a bit of time tracing wires. The easiest thing I found was if you jack the car and place completely on jack stands it's easy to get to the switch. First step was to jump the switch testing the complete circuit, when the lights worked I pulled the switch, 1-1/16 deep socket and replaced it. |
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