Trying to figure out how to test the ignition light and curtesy light time delay switch. The switch only has 3 wires, battery, ground and power out to the lights. The switch is activated by the door switch that grounds out the circuit and then it supplies power to the lights for a period of time. Does anyone know if the resistance in the light is what causes the switch to heat up and open? I think this is how it works. My dash is all apart now because I have the windshield out and removed the dash pad to fix the windshield frame so I thought it would be a perfect time to do all my under dash stuff. I don't remember this switch working before but I'm not sure. I just want to test it before I reinstall and find out it isn't working. The other question is if the switch works the way I suspect with the bulb resistance causing the switch to heat up and open I would assume an LED installed in place of the traditional bulb would not create that resistance and the light would stay on all the time? Thoughts?
Time Delay Switch 1970 SF
- Thread starter MONC440
- Start date
As I understand it, the power is applied when the door is opened.
When the door is closed and no power to the timer, it cools down and then once cool enough, it opens the switch and the light goes off.
Considering the consistency of how long the ign light illuminates, I figured it was a simple clock/timer module. Not related to "heat" or similar. Might even be a calibrated condenser that goes dim when its charge is used up? Which might explain the dimming of the light rather than just turning off (as if a switch was flipped). Not unlike the later "theater dimming" of the dome light that GM started in many 1978 models.
Just some thoughts,
CBODY67
Just some thoughts,
CBODY67
Simple bi-metal contacts, the heat is from the resistance wire wrapped around a bi-metal strip. It has nothing to do with the lamp load, no reason you can't run an LED. When the door opens, providing a ground, the strip heats up fairly quickly, closes the contacts. After the door is closed it takes a minute or two to cool off and opens the contacts. Similar construction to the gauge voltage limiter.
Some pics here
1970 Fury Time Delay Relay
Some pics here
1970 Fury Time Delay Relay
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So to test the relay out of the car if testing with an ohm meter I should have 0 ohms between the light terminal and power? Then if I apply 12 volts to the battery terminal and ground the ground terminal for say 15 seconds then remove the ground, I should then have 12 volts to the light terminal for something like 30 to 60 seconds?
Is this correct?
Thanks
Is this correct?
Thanks
Yep, sounds correct.
So I tested it and had power to the light circuit all the time. I took the tin cover off and could see the points were touching and seamed to be stuck together. I used a small pick and separated them and cleaned the connections with some 320. Plugged it back in and had no power to the light, when I grounded the ground wire it took about 3 seconds and I had power to the light, after removing the ground the power to the light turned off after about 40 seconds. So I guess I fixed it.
72RR GTX, your pics really helped me figure this out. Thanks!
72RR GTX, your pics really helped me figure this out. Thanks!
Glad you got it working. Can’t take credit of the pics however, looks like member @Welder guy here on FCBO posted those several years back.
3175375
Old Man with a Hat
Good thread! I believe that the 69 timer relay is the same.
On a side note, that same electro-mechanical approach to time related switching was pretty common back in that time for various functions, that was the technology of the time. Some examples, as mentioned, cluster voltage limiters, flashers, and the later electrically assisted choke timer/controls. They all suffered from the same types of early failures, burned contacts, stuck contacts, burned/open heating element wires. These days it’s too easy to put together, or buy, cheap semi-conductor-based timing circuits that can be made emulate the original function of these stock type timers but are far more accurate and reliable.
Touched a bit on timer circuits in this video about a modified choke control. Same type of timer board shown could easily be modified to replace the stock key switch lighting time delay relay with no heat output at all and a wide range of timing.
Touched a bit on timer circuits in this video about a modified choke control. Same type of timer board shown could easily be modified to replace the stock key switch lighting time delay relay with no heat output at all and a wide range of timing.
3175375
Old Man with a Hat
Electric clocks too. Often the points in the electric clocks weld together or the electromagnet coil wire can break.
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