For some reason, after my car is warmed up, the reverse lights stay on…after it sits and cools down, they will work normally. I’ve changed the trans reverse light switch a couple times and the result is the same. has anybody dealt with this? Car is a stock ‘56 Dodge Custom Royal, 315 v8, 2 psd power flite.
Disconnect the wire from the switch and warm it up and see if the light comes on. If it does then look at the wiring that goes back to the lights.
Yeah, it's a pressure switch that screws into a port on the side of the transmission. If they're coming on after running for awhile, that would lead me to believe that the problem lies in the transmission itself. Could be something is plugged or such, because there's a buildup of pressure internally enough to replicate the input from being in reverse. The switch is a twin pole, so once the lights get the signal from that switch they come on. This means that in theory they could be shorting out from somewhere else, but the fact that it only happens when the engine is warm tells me that it's likely a mechanical problem, rather than an electrical one. Just to clarify that you are buying the correct switches, here's where I get mine: https://www.ebay.com/itm/322221454443
Yes, That is the same switch I've been buying. I agree, it must be a pressure issue, but how could it hold pressure for hours after the motor is turned off. And when it's in the "stuck on" mode; switching between all gears and neutral, engine running or not running, will not turn the light off. Btw. Trans was reportedly rebuilt prior to my purchase (15 yrs ago), and trans works perfectly. I'm stumped...
That's wild. I can see now why the later cars, 1957-newer, just had the reverse light switch on the pushbutton assembly in the dash. I ran this by my dad, he's been doing 1955-65 Mopars longer than I've been alive, and he agrees that the likely culprit must be either the switch, or deeper in the port that the switch screws into on the transmission. Does this happen every time the engine gets warm after driving around for awhile? Or just occasionally?
The switch pictured a few posts back appears to have teflon sealing tape wrapped around the threads. Could a piece of that gotten loose and pushed inside the switch? Maybe try installing a new pressure switch with nothing on the threads.
Those switches are terrible. The aperture seems to be the right size to trap dirt- once it gets in it tends to pack the diaphragm and cause it to be sticky. Might be it's just oil canning with the heat and making contact.
Yup, happens every time. At least until I unplug it because I don’t want to distract people driving behind me! So I wait a couple years and buy a new switch, only to have it happen again. I’m on my 3rd switch. I think I’ll try screwing a pressure gauge in there and seeing what and when it reads…
PhilA may be onto something, maybe the switch just can't take the heat and when it gets hot it stays closed. Maybe you could add an extension pipe to it to help get away from the heat or...... I would try a pressure switch from a GM 700r4. There were switches that were 2 pole normally open, among other styles that had to do with lockup control. They were designed to be internal and in the heat and are 1/8NPT. Bill
That’s what I thought. That it was a substandard chinese switch and wasn’t up to the task. If a gauge goes to 0 when the car is turned off, I’ll know it’s the switch. Maybe the opening could be drilled out a little? Maybe it needs a 90 or a 45 to get it above the fluid?
I wouldn't go through all that work to put a pressure gauge on the trans. Depending on what circuit the switch gets its signal from, if its in the actual reverse circuit, the pressures are well in excess of 200LBS. I would get it to act up and keep the light on, remove the wires and Ohm the terminals to see if the switch is closed, then remove the switch an test again off the car. I bet you will find the switch will still test closed until it cools off. There is no transmission that will hold internal pressure for any extended time, after engine is turned off. Bill
I like that idea even better, but what’s the chance 3 switches over the years having the same problem?
If every single switch was in the same batch, then in theory they're just grabbing the next one in the box to ship to you. Post up a pic of the switch and how close the exhaust is to it. That could be effective functionality as well.
That switch is probably no different than most of the crappy brake light pressure switches that are made today, that just about everyone has problems with. Bill
Have you considered putting in a manual switch for the reverse lights? Just figure out a way to have the trans linkage move a manual switch, like a manual brake light switch to turn on and off the reverse lights.
I've definitely thought about it, wouldn't be very ez so I'm trying to give the stock set up my best effort.
High. They're cheaply made, and I've always considered them to be somewhat a service part, expect failure.
The switch probably has a metal diaphragm that move to make/break the contacts when under pressure. Or in your case, gets up to trans operating temp. I wouldn't be at all surprised to find that it wasn't built for that application, just adapted from another by some aftermarket parts genius.
It's the switch. I drove the car, light came on. Tested the switch with an ohm meter, switch was closed. Removed the switch (no pressure behind it), tested again - still closed. Put it in the freezer for 10 minutes and it tested open. Junk, just like everyone has been saying. Now the hunt begins for a modern pressure switch !
How about running a coiled copper line from the transmission port over to the frame and plumb the switch into the end of the line. That should get it away from the heat of the transmission, and with the coiled length of the copper tube should cool the oil so the switch works correctly. Make up a mount for the switch and done.
It’s not the heat just crappy switches . forklifts still use pressure switches in the brake system for lights . The factory switch lasts 20-30 years the replacement no matter after market or oem become a serviceable part and we replace them regularly until the customer gets upset and just run the lift with no brake lights . sucks , but it’s the world we live in . I would try a manual switch either actuated up by the dash or down by the Tranny pawl someplace .
Yeah, your exhaust is far enough away that the heat levels are totally normal. Unfortunately the ones I have don't have part numbers on them, so I can't tell you what the pressure is meant to be to initiate the switch. I believe your only way to check that would be to install a cheap 100psi gauge (about $20-30) and see what the reading is when it's running vs shifting into reverse. And then shop around from there. Otherwise you can just start installing universal switches and see what seems to work.
There’s two types of those switches, normally open and normally closed. Normally open are off until pressure hits them, then they complete the circuit. Normally closed break the circuit when pressure hits them. Both kinds are used on semi trucks albeit with air pressure instead of oil. The factory ones last a long time, but the replacements only last a year or two. I usually kept a few in the truck with me because they will fail without warning, leaving you without brake lights or other functions. I was buying mine from the Freightliner dealer, like everything else nowadays they were imports. Their computer didn’t list which ones were which, only the location where they fit, so I had to do a little sleuthing to figure out which was which, open or closed.
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