www.wholelattelove.com: our caffeinated commitment to you

Loose electrical connectors = overheating connections

Postby SNielsen on Mon Dec 10, 2007 4:58 pm

Not sure if anyone has written about this topic before on these forums, but I wanted to share something I found in my recent inspections and maintenance on my newly-acquired used Giotto. I discovered that several of the plastic protectors covering electrical connectors inside the machine were quite badly discoloured. Most were normal - ie. pale amber colour or off-white (those away from the boiler heat). But at least four were a dark brown colour, esp, at the bottom where the actual female spade connector fits on the male terminal. You can see this in the following picture:

Image

Turns out that this discolouration was actually an indicator of the real problem, which in my case was overheating connections caused by loose connectors. To check this, I wiggled all the spade connectors in the machine, and sure enough, those with the dark brown discolouration were loose, and those with normal colour were nice and tight. For those not familiar with electrical matters (I'm no expert, but I know the basics), when current flows through a poor connection, it meets resistance, and the resistance creates heat. Hence the overheating at the connector.

For most of the loose connections that I found, it was simply a matter of the compression arms or wings (for lack of a better term) on the female spade connector having become loosened over time. But in one instance (see photo below) there was also corrosion on the male terminal.

Image

(Sorry for the poor picture quality - couldn't get my camera to focus on the foreground, but you get the idea)

The fix for this is fortunately easy. In my case, I was able to slide the plastic protectors off the spade lugs and gently squeeze the arms tighter with a pair of pliers. This tightened their grip on the male terminal - ie. it improved the connection by increasing the compression on the terminal. Several of the plastic sleeves were very brittle from the heat, and just crumbled when I pressed on them (I will replace these soon). An alternative would be to simply snip off the wire at the spade lug, strip bare some fresh wire and crimp new connectors on, but you would need good crimping pliers. You would probably only want to do this if the lug is badly corroded. If there is no corrosion, squeezing the connector is easier.

For the corroded male terminal in the photo above, I cleaned the connector by gently rubbing with fine steel wool and emery paper. It polished up nicely and all the crud was gone, leaving a nice shiny terminal.

After tightening all the loose spade lugs, they fit on their terminals as tightly as the rest of the connectors. I now have confidence that the connections are secure and that I won't have reliability problems from this source. I'll check on them periodically whenever I open up the machine for maintenance.

For anyone with a machine a few years old, it would probably be a good idea to check for this next time you open up the machine. Hope this helps.

Regards,

Svend
SNielsen
 
Posts: 26
Joined: Dec 04, 2007
Location: Ontario, Canada

Postby cafeIKE on Mon Dec 10, 2007 6:17 pm

The source of the problem is more than likely the vacuum breaker that spit water onto the main thermal breaker as the system heated. The wire may have wicked up some moisture, creating a hidden future failure point.

SNielsen wrote:An alternative would be to simply snip off the wire at the spade lug, strip bare some fresh wire and crimp new connectors on, but you would need good crimping pliers.

Replacing the bad wires is the best option. Unless the wire have lots of excess service loop, they may be too short after trimming back to good wire.

SNielsen wrote:You would probably only want to do this if the lug is badly corroded. If there is no corrosion, squeezing the connector is easier.

The metal in the connector is probably fatigued from repeated heating and cooling cycles and retains insufficient tension to maintain a solid connection. The composition maybe degraded from electrolysis. Junk 'em!
User avatar
cafeIKE
 
Posts: 3084
Joined: Jun 27, 2006
Location: Woodland Hills, CA

Postby SNielsen on Mon Dec 10, 2007 7:58 pm

The source of the problem is more than likely the vacuum breaker that spit water onto the main thermal breaker as the system heated.


This wasn't the only loose connector. There was one on the boiler element, and one on the Pstat as well. which is quite far from the vacuum breaker. The corroded male terminal in the picture was, however, the only such terminal that I found -- all others were sound.

The metal in the connector is probably fatigued from repeated heating and cooling cycles and retains insufficient tension to maintain a solid connection. The composition maybe degraded from electrolysis.


I agree about the metal fatigue from heating/cooling. There is no other mechanism in such a machine to cause connectors loosening. Are you saying that tightening the spade with pliers isn't enough to ensure a good connection? As for electrolysis, just by looking at the spade lugs they seemed fine. How can I tell if they've degraded?

Svend
SNielsen
 
Posts: 26
Joined: Dec 04, 2007
Location: Ontario, Canada

Postby cafeIKE on Mon Dec 10, 2007 9:31 pm

SNielsen wrote:I agree about the metal fatigue from heating/cooling. There is no other mechanism in such a machine to cause connectors loosening. Are you saying that tightening the spade with pliers isn't enough to ensure a good connection? As for electrolysis, just by looking at the spade lugs they seemed fine. How can I tell if they've degraded?

Other than putting a lot of current through them and seeing how they hold up, you can't.

Do you want a machine that you _KNOW_ has good wiring and connectors or continually worry about some ha'penny connector frying itself, the wire coming loose, arc welding itself to the boiler and your defective house breaker lighting up the wiring in your walls?

Do it right the first time :!:
It could be better than 'factory' :wink:

p.s. better replace the over temp breaker as well. Then make a shield for the vacuum breaker so any spurious droplets rain harmlessly down into the bottom of the machine. A short length of PVC could do nicely.

p.p.s. ALL internal wiring should have a drip loop so any water that does collect on a wire runs to the bottom of the loop and drips off harmlessly and cannot run down the wire to the connectors.
User avatar
cafeIKE
 
Posts: 3084
Joined: Jun 27, 2006
Location: Woodland Hills, CA

Postby SNielsen on Mon Dec 10, 2007 11:02 pm

Excellent advice! Thank you. I stand corrected on several points. I've got an order in for some parts for the machine, and I've already added some new connectors w. plastic protectors to the shipment, so that will take care of the funky ones currently in the machine. Great idea on the plastic guard for the vacuum breaker.

Cheers,

Svend
SNielsen
 
Posts: 26
Joined: Dec 04, 2007
Location: Ontario, Canada

Postby lennoncs on Tue Dec 11, 2007 1:37 am

relaxation/annealing is a common problem with terminals that are not designed for operation at extended temperatures.

all the terminals should be either high nickel or ring terminals that are bolted and silver soldered if not a high temp material.

Also;
a proper crimp goes a long way to keeping junctions cool and happy...don't over-crush 'em.

I would really urge people to take the time to use proper terminals for these machines....It makes me sick to hear about smoking machines.


Sean
Sean Lennon
Davisburg Mi.

LMWDP #086
lennoncs
 
Posts: 219
Joined: Jun 29, 2005
Location: Davisburg, Michigan

Postby cafeIKE on Tue Dec 11, 2007 2:08 am

lennoncs wrote:a proper crimp goes a long way to keeping junctions cool and happy...don't over-crush 'em.

Amen. Entire volumes have been written on making proper crimps. For high current applications, it's mandatory to have terminals correctly sized for the wire, the correct crimp die AND a tool that applies the correct compression for the terminal / wire combination.

Additionally, purchasing FastOn types from the same manufacturer can avoid tolerance problems and help ensure the best connection possible.
User avatar
cafeIKE
 
Posts: 3084
Joined: Jun 27, 2006
Location: Woodland Hills, CA

Postby DavidMLewis on Tue Dec 11, 2007 3:33 pm

People will think I'm a shill for these folks, which isn't true, but Stabilant has proven remarkably effective in this sort of service. I have a Ducati Monster whose headlight connector is legendary for melting due to the connector getting slightly corroded and the resulting resistance heating it. On many units, a bit of Stabilent eliminated the problem. The cheapest source I've found in the US is Posthorn Audio in New York City. Sounds like snake oil but really isn't, and while it's expensive, so little is used that a bottle lasts for years.

Best,
David
DavidMLewis
 
Posts: 515
Joined: May 08, 2005
Location: Portland, Oregon