# How is the Clutch Interlock switch supposed to work?



## dbsoundman (Feb 3, 2013)

For some reason, on my 88 pickup I can start the truck without the clutch in all the time. I see the Clutch Interlock switch, but it seems to be a momentary switch -- as soon as I let go, it returns to its original position. How is it supposed to work in normal circumstances?

Also I should note I don't have a traditional starting scheme in this truck -- someone bypassed the START position on the ignition switch and replaced it with a button, so you just turn the key to ON, then press the button to start. Apparently that ignition switch is super expensive and the previous owners just didn't want to pay for a new one, so they wired in the switch instead...


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## TheRepairMan (Jun 30, 2009)

Sounds like you already know why you can start it with the clutch in any position ...someone bypassed the clutch safety switch and relay when they put the push button switch in.

I'm guessing they were having problems getting the truck to crank... which could have been the ignition switch, or may have been the clutch switch or the interlock relay itself. That interlock relay failed on mine just a few weeks after I bought my truck from its previous owner. Took me a little bit to figure the problem out, but I found out it was a pretty common problem. I think the relay was like $15 aftermarket at the time, but it is a one of a kind unlike common relays for on parts store shelves.

-R


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## dbsoundman (Feb 3, 2013)

Good to know! Is there any reason I would want to fix it, ie is it bad to start without the clutch all the time?


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## TheRepairMan (Jun 30, 2009)

The obvious problem happens when someone tries to start the vehicle with the clutch out and it's in gear ...so, it's a safety issue. Now, most of us would never try to crank one up without pushing the clutch in, but there's always that chance. That's all the interlock system was there for... to prevent accidental starting in gear. I vaguely remember some trucks years ago that even had a rocker switch on the dash to over-ride the clutch safety switch for emergencies. But, yeah, if you wanted to you could put it back to stock working order.

-R


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## D21me69 (7 mo ago)

Ok I realize this thread is 9 years old, however I have a relating issue and also by the way the interlock switch had a few uses that actually were very good to have. first let's say your engine blew completely while driving and now your jacked up truck with 33s is stuck in the road, all you had to do was turn key to on click the interlock once and while in first gear turn the key to engage starter, the truck will easily move maybe 30 feet or more before battery is drained. If you have ever wandered why many Nissan starters are 5 times larger and usually more expensive than other vehicles this is why, even small d21 trucks have way bigger starters than say your 3500 dodge V8 vans. 
Anyway my issue is this, I believe I may have had 2 Ecu's burn out possibly from previous owners shabby wiring. And at the same time as one of the ECU started acting very and bad dumping way too much fuel into the engine my interlock switch suddenly stopped working, maybe a coincidence but how likely is it that this is related? 
If anyone still monitors this thread, anyway thanks please help 🙂


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## TRM356 (7 mo ago)

D21me69 said:


> Ok I realize this thread is 9 years old, however I have a relating issue and also by the way the interlock switch had a few uses that actually were very good to have. first let's say your engine blew completely while driving and now your jacked up truck with 33s is stuck in the road, all you had to do was turn key to on click the interlock once and while in first gear turn the key to engage starter, the truck will easily move maybe 30 feet or more before battery is drained. If you have ever wandered why many Nissan starters are 5 times larger and usually more expensive than other vehicles this is why, even small d21 trucks have way bigger starters than say your 3500 dodge V8 vans.
> Anyway my issue is this, I believe I may have had 2 Ecu's burn out possibly from previous owners shabby wiring. And at the same time as one of the ECU started acting very and bad dumping way too much fuel into the engine my interlock switch suddenly stopped working, maybe a coincidence but how likely is it that this is related?
> If anyone still monitors this thread, anyway thanks please help 🙂


I'm not sure what the question is. It sounds like you have many, but if you are asking if the Clutch Interlock Switch could cause the ECU to fail... I don't see how it could. I think it just interrupts power to the Starter Relay for safety reasons.


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