Momentary primer switch wiring

[khedrei]

The plastic on my momentary primer switch in my 231 is brittle and falling apart. It's not a Klixon CB type switch even though it's the same size and shape and mounting configuration so I am not able to replace the cover.

I would like to replace it with a Klixon CB switch and simply buy an engraved cover for it so everything looks nice and new but it has 4 terminals on the back of it. One terminal is simply jumped to the other and I'm not sure exactly where the other wires go. The avionics guy rewired it after my panel was done. Not sure why a two position switch has 4 terminals.  Aside from losing the momentary function of it would it hurt to replace it with a CB switch that has the same amp rating as the low or high boost?

Anyone have a wiring diagram for the primer switch?

[carusoam]

Compare to the drawing supplied by Klixon, available on the inter webs...

There are probably extra legs on that one too...

Expect a like for like swap...

Post a pic of what you have...  somebody will recognize it...

Best regards,

 -a-

[Guest]

It sounds like a double pole, single throw switch.  Isn’t it supposed to be a momentary contact switch?  If so, I don’t think replacing it with a C/B switch would be legal.

Clarence

[DanM20C]

10 hours ago, khedrei said:

I would like to replace it with a Klixon CB switch

Clarence is correct,  you cannot replace it with a Klixon CB switch.  Nor would you want to if you are a CB like myself, those switches are ridiculously expensive. 

The switch is a momentary, double pole, single throw. (DPST) The power to the switch is protected with a 10amp breaker labeled "primer".  One pole energizes the high boost and the other poll energizes the primer diverter valve sol.  So with the original primer, the switch activates the hi boost while diverting fuel to the primer circuit. If you complied with the CSB19-01 your diverter valve would have been removed and the primer switch now just acts as a momentary hi boost switch. If you complied with the SB you could replace the switch with a SPST momentary switch. 

I recommend performing the SB to remove the diverter valve.  My airplane starts easier without it and the fuel system is simplified. 

Cheers,

Dan

[khedrei]

The main reason I wanted to use the Kilixon switch is because I have 2 extra kicking around. Obviously I need it to be legal. My high boost has a cover with momentary spring on it that can be pushed to the side. If it's just a momentary issue that can be solved. But in terms of the connection, could it not be hooked up so the fuel pump and diverter sol be wired to the same contact so they activate at the same time? 

I will have a look at that SB and see what I can do.  Right now I havent even been able to find a replacement 4 pole momentary switch to fit.

As for the 10A circuit breaker, I dont see it wired to any...

[DanM20C]

1 hour ago, khedrei said:

As for the 10A circuit breaker, I dont see it wired to any...

My mistake, it has a 10amp fuse.  It should be mounted in an inline fuse holder someplace behind the panel.

1 hour ago, khedrei said:

My high boost has a cover with momentary spring on it that can be pushed to the side. If it's just a momentary issue that can be solved.

The high switch should not be a momentary switch, but it should have a red safety cover to prevent you from turning it on without thinking about it.  The engine will not run (flood) with high boost on except at high power settings.

1 hour ago, khedrei said:

But in terms of the connection, could it not be hooked up so the fuel pump and diverter sol be wired to the same contact so they activate at the same time?

No, that would cause the diverter valve to energize any time the high boost was used.  Essentially turning the high boost switch into a primer switch.

I just checked the IPC and found this number for the primer switch.  TIGK6B-1F-WH-A    A quick google search and it seems one should be easily had for not too much $.  

Cheers,

Dan

[khedrei]

Ok that all makes more sense. Thanks very much for explaining it that way. I can see why the extra pole is required. I found an inline fuse near the high boost switch. 

My high boost isnt a momentary but it has a safety cover which the installer didnt even put in properly but it does allow the switch to be depressed slightly to engage and can move sideways in order to engage fully.

How long does it take to remove the diverter for the SB? would the primer switch remain in place once its removed?

[kortopates]

20 minutes ago, khedrei said:

Ok that all makes more sense. Thanks very much for explaining it that way. I can see why the extra pole is required. I found an inline fuse near the high boost switch. 

My high boost isnt a momentary but it has a safety cover which the installer didnt even put in properly but it does allow the switch to be depressed slightly to engage and can move sideways in order to engage fully.

How long does it take to remove the diverter for the SB? would the primer switch remain in place once its removed?

Once you line up the parts - including a new hose or fuel line and likely new cylinder drain ports (if you have old style), then about an hour not including de-cowling and cowling. It doesn't change the operation of the primer switch for starting, it just puts fuel directly into the cylinders now without the diverter valve, just like Dan said above.

There was a lead time on getting the parts some time ago when this mandatory SB first came out and everyone was complying since TCM mentioned a bad diverter valve had brought down a plane. But the SB has never reached AD status; supposedly FAA is reviewing/considering it. Perhaps getting the parts now will be easier and quicker now.

[DanM20C]

2 minutes ago, khedrei said:

How long does it take to remove the diverter for the SB? would the primer switch remain in place once its removed?

The switch stays in place and is still used.  Like I mentioned above it is just a momentary high boost switch at that point.  The whole diverter valve primer system was a solution to a problem that never existed.

It just takes a few hours to perform the SB. You will need  a new fuel line, 2 plugs for the intakes, and possibly 6 cylinder drains.  You may be lucky and have the correct drains, I don't know when Continental switched but I think it was after the GB/LB's. 

I have attached the SB, it clearly shows the different drains.

Cheers,

Dan

CSB19-01A.pdf

[khedrei]

Thanks guys.

Since the high boost pump has a cover with a momentary spring on it allowing momentary function would it not make sense to remove the primer switch completely once the SB has been performed? I suppose if the official paperwork says "no" then that would make it illegal to do. That being said, what's legal isnt always safe and what's safe isnt always legal. 

[DanM20C]

I don’t see a functional problem with removing it. I have no idea of the legality of it. The primer is referred to in procedures in the POH, I could see that causing a problem?  @kortopates will know!

If it legally can be removed I may do it when I cut a new panel later this year. But I do like the convenience of it and it’s location right above the throttle. 
 

34 minutes ago, khedrei said:

Since the high boost pump has a cover with a momentary spring on it allowing momentary function

I’m not intimate with the internal mechanics of the Klixon switch but I wouldn’t not use the guard to operate it in a momentary fashion much. I know others do and maybe I’m being overly cautious. But it’s critical for contacts in a switch to make a good solid contact to prevent arcing leading to Premature wear.  I worry that wouldn’t happen and the switch would wear out faster.  
 

For priming it’s not a big inconvenience to just move the guard and fully engage the switch.  
 

cheers,

Dan