R

Reflex

Well Known Member
Is it permissible to use heat shrink under the cowl?

Specifically, I'd like to connect my oil temp sensor on the back of the accessory case to the lead coming from the GEA-24. These small wires would be perfect the the D-sub pins and heat shrink method. Neat, removable, and simple.

I know we use heat shrink for abrasion resistance and protection in a few places under the cowl, but my concern is temperature where the heat shrink is holding a connection together.

Thanks,

Fred
 
Reflex said:
Is it permissible to use heat shrink under the cowl?

Specifically, I'd like to connect my oil temp sensor on the back of the accessory case to the lead coming from the GEA-24. These small wires would be perfect the the D-sub pins and heat shrink method. Neat, removable, and simple.

I know we use heat shrink for abrasion resistance and protection in a few places under the cowl, but my concern is temperature where the heat shrink is holding a connection together.

Thanks,

Fred
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What type of connection is on the oil temp sensor? The sensor on my engine takes a ring terminal and that is all I would use to avoid making a separate connector junction.
 
There's a mil-spec for heat shrink. Assuming it meets that mil-spec it takes around 250f to shrink it and it has to hold up to around 275f (this is from memory, so I might be off a bit).

I doubt that the top of engine is getting that hot, except maybe if it heat soaks after shutdown, but thats just a guess on my part. You could give it a try with a couple of layers of heat shrink and see how it holds up, but it's not like you need to disconnect that sensor a bunch. I think a better solution would probably be to just leave a service loop there and use simple butt splices or raychem E splices,
 
It's just two wires with no ends. Picture below:

Oil Sensor.jpg
 
Gents,

Thanks for your replies.

Terry, hope things are going well, you've got some nice weather for working in the hangar today.

Yes, there's a mil spec. In fact, I see McMaster-Carr offers some heat shrink that has an upper working limit of 500 degrees. Tefzel covering has a working limit of 302 degrees F. However, we use solder splices on it so I figure exceeding the working temp on occasion isn't going to hurt it. However, the high temp shrink from McMaster shrinks at 620 degrees F....that may be a bit of concern with Tefzel.

I purchased several of the Raychem splices you showed me. I like them but was hoping for something more removable/serviceable. I agree that this should rarely if ever need to be serviced. I like the Raychem splices, just thought it would make things really easy if I could do it with shrink tubing. I tried using/testing the plastic "shrinks" that came with the Raychem splices with D-Sub connectors, but they're just about 3/16 to short to cover properly.

Don't really want to leave a service loop as it's getting crowded in there!

Thanks,

Fred
 
Gotcha. If you want, you could just use a couple of layers of regular heat shrink and see how it holds up. I seriously doubt if it's going to get hot enough to bother it. There's almost no current running through there so if it comes apart the worst that can happen is that your oil temp indication will suddenly go screwy. If that happens you'll know where to look.

You could also just use insulated spade connectors or even a 2 pin molex connector. Lots of ways to do it.

edit- Not just in this instance, but wherever space is limited, there's nothing to say that a service loop has to be right at the end of the wire. You can fold it back on itself a couple of times somewhere closer to the firewall. It's potentially a bit more work on down the road, but if you need it later you just have to remove the wire ties or adel clamps or whatever from the termination to wherever you've left yourself some extra wire and pull out the slack.
 
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Desert Rat said:
Gotcha. If you want, you could just use a couple of layers of regular heat shrink and see how it holds up. I seriously doubt if it's going to get hot enough to bother it. There's almost no current running through there so if it comes apart the worst that can happen is that your oil temp indication will suddenly go screwy. If that happens you'll know where to look.

You could also just use insulated spade connectors or even a 2 pin molex connector. Lots of ways to do it.

edit- Not just in this instance, but wherever space is limited, there's nothing to say that a service loop has to be right at the end of the wire. You can fold it back on itself a couple of times somewhere closer to the firewall. It's potentially a bit more work on down the road, but if you need it later you just have to remove the wire ties or adel clamps or whatever from the termination to wherever you've left yourself some extra wire and pull out the slack.
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Agreed. Thanks Terry!
 
OK. Get me smarter because I'm not seeing the need for the connectors mentioned.

This device and associated connection does not need regular servicing/disconnection; like engine removal only. It is a TC -> passive sensor -> millivolt output. You want to minimize added resistance in the leads andd associated connections to minimize error.

What's wrong with HS tube over butt splices and a 1"D service loop?
 
HD Aviation Supply shrink tube working great in the top plenum right above cylinder 3 for the past 300 hrs. Protecting the oil temp sensor spade connectors. No indication of over heating.
 
Desert Rat said:
There's a mil-spec for heat shrink. Assuming it meets that mil-spec it takes around 250f to shrink it and it has to hold up to around 275f (this is from memory, so I might be off a bit).

I doubt that the top of engine is getting that hot, except maybe if it heat soaks after shutdown, but thats just a guess on my part.
Click to expand...

I’ve tested with a thermocouple, 104deg. day, shut down on the ramp, facing away from any breeze. It doesn’t get that hot.

I did this after a few people “chimed in” after seeing a post, unrelated, to tell everyone how bad it was to have a Floscan mounted on top of the engine in the plenum. They hadn’t tested, just assumed….. I beleive they probably still think that way today, and still haven’t tested it…. “It won’t last long”….. 900 plus hours later……. doing just fine.
Heat shrink is just fine FWF.
 
There are all kinds of different temperature ratings for heat shrink tubing. Take a look at this DigiKey page. The operating temperature range and shrink temperature are way over to the right, so scroll over to see them.
 
RV6_flyer said:
I would NOT splice. I would put a connector on to make replacement easy when it breaks.
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I don't recall ever replacing a bad oil temp sensor.
Correctly installed butt splices are bullet proof unlike connectors, also super easy to cut/splice in new ones if you leave a little service loop in your wiring like you should.
 
Reflex said:
Is it permissible to use heat shrink under the cowl?

Specifically, I'd like to connect my oil temp sensor on the back of the accessory case to the lead coming from the GEA-24. These small wires would be perfect the the D-sub pins and heat shrink method. Neat, removable, and simple.

I know we use heat shrink for abrasion resistance and protection in a few places under the cowl, but my concern is temperature where the heat shrink is holding a connection together.

Thanks,

Fred
Click to expand...
Cub Crafters use heat shrink to join the intake manifolds to the sump. Use digikey to research some high quality heat shrink, they have a good selection and generally list the specs. I like the raychem products, Aerodon
 
Aerodon said:
Cub Crafters use heat shrink to join the intake manifolds to the sump. Use digikey to research some high quality heat shrink, they have a good selection and generally list the specs. I like the raychem products, Aerodon
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If anybody is worried about heat shrink giving problems, get the 3-1 shrink with adhesive lining and it will never come off, even when you want it to.
It is pretty tough stuff.
But my luck varies Fixit
 
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