Almost there…

I totally finished off all of the wiring on my new X-Air panel today. Yesterday I’d left off the connections to the EGT gauge but on reflection, I decided that this would be unwise. I’ve ordered some new senders from the UK as the ones available over here are 50% or so more expensive. I can have them delivered from the UK for less than the cost of just the senders bought locally before adding carriage. All of the other panel connections are made by flying leads and if I left the EGT sender connections off, it would be difficult to fit them when the time comes without removing the whole panel again, which I obviously don’t want to do 😐

So I decided I should make the EGT sender connections in the same way, using flying leads. I happened to have a short length of light 4-core cable that I bought in Maplins quite a while ago and as the EGT gauge needs two pairs of connections, this was an ideal start. However, the cores are extremely light, which is fine for the tiny currents generated by the EGT sender thermocouples, but I needed to find a way of making connections that would be strong and at the same time resilient enough to employ the usual crimp-on plug-in type connectors. I did it by soldering the connections straight onto the pins on the back of the gauge (easy with my nice new high power soldering iron), strengthening them with rubber shrink-sleeving and then holding that end of the cable solidly in a fixed position by connecting them to the heavier cables of the main bunch with cable ties. I then needed to boost the size of the cables at the other end so they could take the crimp-on connectors and I did this by separating the cables into two pairs, soldering on some heavier cable ends that would take the crimp-on connectors and methodically strengthening the weak cables and the soldered joints with shrink-sleeving as I went to give me the overall strength that I needed. I was very happy with the result which I think will work fine. All I’ll need to do when I have the new senders will be to cut them to length and add crimp-on sockets to make the final connections. Here are a couple of pics that show what I’m talking about.

I’ve tested the wiring on the bench and it all seems to be fine, except I’ve made one logical slip-up. The hour meter takes power from the starter switch but can only work when the mag switches are ‘on’ ie not earthed, as only then is an earth made for the hour meter. This means that with the mags ‘off’ the hour meter won’t keep running even if the starter switch is inadvertently left in its ‘on’ position. For convenience, because the cables were in close proximity, I’ve connected the hour meter and car cigar lighter sockets to a common earth. However, I hadn’t realised that this means that the power socket will only be live while the engine is running which would not be a disaster as it’s only intended to run a GPS while in flight. However, the DIN socket becomes live when the ‘aux’ switch is turned on independently of any other switch except the master, which is how I intended both power sockets to work, and I think I’ll modify the car cigar lighter socket earth tomorrow so it works in the same way. Best to do it now because if I leave it I’m sure I’ll regret it later 😉