Clutch Switch Bypass For Big Blue

[Gary Lewis]

https://forum.garysgaragemahal.com/file/n150093/Clutch_Safety_Bypass.jpg

Not that I'm trying to avoid being right , and I'm a little rusty reading automotive schematics. But if you put a diode in the wire between the "top" side of the clutch switch and the "COM" terminal on the junction block I'm thinking that would still allow the signal from the ignition switch to go through (when the timer relay is closed) but would not allow the LED to ground through the clutch switch and starter relay. So would that avoid the annoying LED shining when you hit the clutch? Or am I rustier than I thought?

Bob - You are right about the diode allowing the module's relay to bring in the starter relay but keep the LED from coming on when the clutch is depressed. But it would allow the LED to come on when the module's relay was pulled in. Well done!

That might just be enough positive for me to keep the module and add the capacitor. I can get 3300 mfd capacitors easily, and that might be just enough to keep power on the relay through the Run/Start gap.

Thanks! That opens up new possibilities.

[Nothing Special]

Bob - You are right about the diode allowing the module's relay to bring in the starter relay but keep the LED from coming on when the clutch is depressed. But it would allow the LED to come on when the module's relay was pulled in. Well done!

That might just be enough positive for me to keep the module and add the capacitor. I can get 3300 mfd capacitors easily, and that might be just enough to keep power on the relay through the Run/Start gap.

Thanks! That opens up new possibilities.

As I've said, more and more I find myself gravitating to the simplest solutions. But I still really like the elegant ones. I'm not trying to talk you out of a simple switch and indicator light, but I know you want a nice, elegant solution, so I don't want you to give up on it unless you WANT to give up on it.

And speaking of simple vs. elegant, rather than capacitors is there a "cleaner" source of power you could use? Something that doesn't drop out when switching to Start? I'm thinking your three general options are Ignition power, Aux power or unswitched power.

I'm thinking Aux power is only hot when the key is in the Run position (or the Aux position on the other side of Off and Lock). So I don't think that's an option. But if it is hot during Start maybe that's what you're using?

I'm guessing you are using Ignition power, because I'm thinking that's the only switched power source that hot in both Run and Start. But if you are using Aux (see above), maybe Ignition doesn't drop out as you go from Run to Start? Just a thought, but it might be worth looking into.

And you should be able to get completely away from any problems of the power dropping out if you use unswitched power. That would mean that the timer module is always getting power, and therefore always draining the battery. But if it's solid state, does it draw so little power that it's not a problem? I'm not saying this will work, and you certainly don't want to trade needing to add capacitors for a dead battery! But soething else to think about over your third cup of coffee!

[Gary Lewis]

As I've said, more and more I find myself gravitating to the simplest solutions. But I still really like the elegant ones. I'm not trying to talk you out of a simple switch and indicator light, but I know you want a nice, elegant solution, so I don't want you to give up on it unless you WANT to give up on it.

And speaking of simple vs. elegant, rather than capacitors is there a "cleaner" source of power you could use? Something that doesn't drop out when switching to Start? I'm thinking your three general options are Ignition power, Aux power or unswitched power.

I'm thinking Aux power is only hot when the key is in the Run position (or the Aux position on the other side of Off and Lock). So I don't think that's an option. But if it is hot during Start maybe that's what you're using?

I'm guessing you are using Ignition power, because I'm thinking that's the only switched power source that hot in both Run and Start. But if you are using Aux (see above), maybe Ignition doesn't drop out as you go from Run to Start? Just a thought, but it might be worth looking into.

And you should be able to get completely away from any problems of the power dropping out if you use unswitched power. That would mean that the timer module is always getting power, and therefore always draining the battery. But if it's solid state, does it draw so little power that it's not a problem? I'm not saying this will work, and you certainly don't want to trade needing to add capacitors for a dead battery! But soething else to think about over your third cup of coffee!

I'll think about that over my 2nd cup. First cup is almost gone and I'm headed to the kitchen for more.

 

[Gary Lewis]

As I've said, more and more I find myself gravitating to the simplest solutions. But I still really like the elegant ones. I'm not trying to talk you out of a simple switch and indicator light, but I know you want a nice, elegant solution, so I don't want you to give up on it unless you WANT to give up on it.

And speaking of simple vs. elegant, rather than capacitors is there a "cleaner" source of power you could use? Something that doesn't drop out when switching to Start? I'm thinking your three general options are Ignition power, Aux power or unswitched power.

I'm thinking Aux power is only hot when the key is in the Run position (or the Aux position on the other side of Off and Lock). So I don't think that's an option. But if it is hot during Start maybe that's what you're using?

I'm guessing you are using Ignition power, because I'm thinking that's the only switched power source that hot in both Run and Start. But if you are using Aux (see above), maybe Ignition doesn't drop out as you go from Run to Start? Just a thought, but it might be worth looking into.

And you should be able to get completely away from any problems of the power dropping out if you use unswitched power. That would mean that the timer module is always getting power, and therefore always draining the battery. But if it's solid state, does it draw so little power that it's not a problem? I'm not saying this will work, and you certainly don't want to trade needing to add capacitors for a dead battery! But soething else to think about over your third cup of coffee!

Yes, I'm using "Ignition" power, in theory because it would be hot in both Run & Start. But it isn't during the transition.

And I'd thought about powering the module at all times, but there's already enough electronics in the truck that I keep it on a charger when in the shop. (I think it is the camera system, mainly, which has a cutoff voltage 'cause it knows it'll pull the system down over time.) So I'm reluctant to add to it. And it is no fun wiring up under the dash in order to change power sources.

The way I have power to the module wired with 1/4" male/female connectors, it would be easy to insert a diode/cap combo in the middle w/o even getting into the box, which requires pulling the horse collar trim piece below the column, which requires loosening the instrument bezel, which requires removing the headlight and wiper knobs. But to put the diode in, which I really like by the way, I do have to pull all of that.

So the easiest approach is to make up the diode/cap circuit and add it 'tween the two 1/4" connectors, then pull the stuff off to add the diode - if the diode/cap combo fixes it.

I see some 3300 mfd caps on Amazon so think I'll order a set of them in and make up the circuit with jumpers. If that works well enough I'll make it quasi permanent and then put the diode in the clutch switch circuit. Might as well since I'm close to having the elegant solution working well.

[viven44]

I'll think about that over my 2nd cup. First cup is almost gone and I'm headed to the kitchen for more.

I just looked at your schematic and understand it now. I have had the worst luck with "Bosch relays that aren't from Bosch". Have you done a sanity check to ensure the resistance between 30 and 87 is indeed <1 ohm when the timer is activated? Maybe check it 10 times to be sure the resistance value has no variation....

 

[Gary Lewis]

I just looked at your schematic and understand it now. I have had the worst luck with "Bosch relays that aren't from Bosch". Have you done a sanity check to ensure the resistance between 30 and 87 is indeed <1 ohm when the timer is activated? Maybe check it 10 times to be sure the resistance value has no variation....

I'm pretty sure it is the drop in power that does it, not the relay itself. I say that because you can see the LED come on when you push the "arm" button when in Run, and then go out as you go to Start.

And because w/o a 1000 mfd capacitor it works ~1/3 of the time. With a 1000 mfd cap it works ~2/3 of the time. With two 1000 mfd caps in parallel it works almost all of the time.

I've ordered 3300 mfd caps and will test with one of them when they come in. But I could make it work even longer if I were to run the LED off the power ahead of the diode so the cap only has to supply the module. That would only take running one more power wire into the box, so if I break into the box to add the diode so the LED doesn't come on with the clutch switch being closed I'll add that as well.

[viven44]

I'm pretty sure it is the drop in power that does it, not the relay itself. I say that because you can see the LED come on when you push the "arm" button when in Run, and then go out as you go to Start.

And because w/o a 1000 mfd capacitor it works ~1/3 of the time. With a 1000 mfd cap it works ~2/3 of the time. With two 1000 mfd caps in parallel it works almost all of the time.

I've ordered 3300 mfd caps and will test with one of them when they come in. But I could make it work even longer if I were to run the LED off the power ahead of the diode so the cap only has to supply the module. That would only take running one more power wire into the box, so if I break into the box to add the diode so the LED doesn't come on with the clutch switch being closed I'll add that as well.

The LED will come on even if there was 100+ ohm in series (as you have established with the starter coil resistance)

I would still measure the relay resistance between 30 and 87. Just returned a brand new switch out of box last week as it was measuring 10 ohms contact resistance. The 46 year old factory one was measuring 1.6 ohms but still letting things function on my rear window on the bronco and with alternator 14V it overcomes any vtg drop. This is the upper limit safety switch.

I haven’t thought much and I don’t know how you are using the cap but just a gut feel you are using a cap you are overcoming a potential resistance drop. My humble hypothesis.

Edit: Just had time to read you are using the cap as a buffer to Power VCC on the module... not the power feed to the starter relay itself. In this case, it would indeed make sense that the timer is cutting out between Run/Start.

If that is the case, while holding key in start (crank) when you push the "arm" button it should crank the starter, right ?

[Gary Lewis]

The LED will come on even if there was 100+ ohm in series (as you have established with the starter coil resistance)

I would still measure the relay resistance between 30 and 87. Just returned a brand new switch out of box last week as it was measuring 10 ohms contact resistance. The 46 year old factory one was measuring 1.6 ohms but still letting things function on my rear window on the bronco and with alternator 14V it overcomes any vtg drop. This is the upper limit safety switch.

I haven’t thought much and I don’t know how you are using the cap but just a gut feel you are using a cap you are overcoming a potential resistance drop. My humble hypothesis.

Edit: Just had time to read you are using the cap as a buffer to Power VCC on the module... not the power feed to the starter relay itself. In this case, it would indeed make sense that the timer is cutting out between Run/Start.

If that is the case, while holding key in start (crank) when you push the "arm" button it should crank the starter, right ?

Yes, I'm powering Vcc for the relay module, and using a diode to isolate it from the rest of the truck's electronics. But if I put the LED ahead of the diode it'll cut the load in half.

[viven44]

Yes, I'm powering Vcc for the relay module, and using a diode to isolate it from the rest of the truck's electronics. But if I put the LED ahead of the diode it'll cut the load in half.

I assume the module is not losing VCC power while in Start, just cutting out between Start and Run.. That would certainly make no sense as the timer wouldn't function.

If the module has power while in start, while holding key in start (crank) when you push the "arm" button it should crank the starter, correct ? That will prove the Bosch relay is good.

Still don't get why the LED would cut in and out sometimes... that's why I've been so hung up on the Bosch relay

Overall I get that the 2 options are 1) cap or 2) find another source to power the module... cap does make more sense. Thanks for bearing with my questions. Interesting problems. Love them.

[Gary Lewis]

I assume the module is not losing VCC power while in Start, just cutting out between Start and Run.. That would certainly make no sense as the timer wouldn't function.

If the module has power while in start, while holding key in start (crank) when you push the "arm" button it should crank the starter, correct ? That will prove the Bosch relay is good.

Still don't get why the LED would cut in and out sometimes... that's why I've been so hung up on the Bosch relay

Overall I get that the 2 options are 1) cap or 2) find another source to power the module... cap does make more sense. Thanks for bearing with my questions. Interesting problems. Love them.

I'll check that the engine will crank if I arm the system in Start. It should. But I'm out and about and may not get to check it today.