Terminal corrosion on AC compressors.

[GBDamo]

Been doing some maintenance/service work on AC compressors and one thing that concerns me is the amount of heat at all the various terminals along the start and run circuit.

In brief the the current draw should be anything from ten to twenty amps but I'm often seeing readings 50% higher that this. When viewing the circuit using an FLIR thermal imaging camera there is a lot of excess heat at the spade crimp terminals.

Removing the spades, closing them with pliers and replacing them greatly reduces the heat and resistance but I've noticed all are slightly tarnished.

I'd like to find a none abrasive cleaning solution and a grease that will improve conductivity as well as prevent further corrosion.

I have googled a few products but can't see the sense in reinventing the wheel, i.e. this must be fairly routine in industry and there must be many maintenance sparks out there who do these routinely.

If so can your share some advice or tips for improving the above situation

Thanks

Damion.

 

[bailes1992]

I've had to use a special grease before now on terminations where copper and alluminium are present to minimise corrosion between dissimilar metals. I can't think what it's called now!

Might be with packing out the terminals with such a grease to minimise corrosion.

I use fine wire wool and isopropyl alcohol to prep and clean tarnished copper and terminations.

 

[GBDamo]

Cheers bailes, all the terminals are silver plated so don't want to use abrasives but may have little choice.
Was the grease you used No-Ox-Id ? I've seen this online and was considering getting some.

 

[bailes1992]

I use the same #00 grade wire wool to polish chrome exhaust tips on my cars so I can't imagine it would damage any plating!

 

[Lucien Nunes]

'Spade crimp terminal' means different things to different people. Some mean a 'fork' that fits under a bolt, like a ring terminal but with an open end. If these are heating the crimp connection is faulty and the terminal needs replacing. The other common meaning is a 0.25" push-on receptacle, used singly and in multipole blocks and often found on microswitches, small motors etc. I assume this is what you're referring to as you mention tightening them with pliers.

I am not sure I have ever seen any of these that are silver plated - that is normally reserved for rather higher spec connectors. Most of the ones I use are tin plated, although there are other surface treatments. Like most push-on connectors the actual working contact area is tiny, typically two little dots the somewhere along the length of where the rolled-over edges press on the blades. Literally a fraction of a square millimetre is doing the work, while the rest of the surface has no effect - it's just a heatsink. Engaging and disengaging the crimp once or twice will usually brighten up the area that matters, even if you can't see it

Tightening obviously increases the effectiveness of the contact at the time but will only remain good if a) the contact is gas-tight to stop it corroding and b) the spring tension does not relax with thermal cycling.

a) Might benefit from greasing, as you say, especially if the connectors are exposed to damp and dirt. I've used No-Ox-Id A-Special, or for sensitive stuff Electrolube contact treatment grease, see: Contact Lubricants - 2GX Contact Treatment Grease - SGB | Electrolube - https://www.electrolube.com/products/contact-lubricants/sgb/contact_lubricants/

b) You can't do much about. If the terminals are weakened or their temper is lost, the only solution is to replace. Thermostatically controlled circuits, especially compressors, in which all the connections repeatedly heat up and cool down, are particularly subject to this kind of deterioration. They can be fickle. Some that I have 'tightened' i.e. closed the gap have then gone on to overheat more seriously, because I actually weakened the spring tension. The devil is in the (invisible) detail and it can be hard to predict how well a particular flavour of terminal will survive.
E2A Chromium is very hard and steel wire wool simply slides over it, silver is very soft and wire wool will gouge through it.

 

[GBDamo]

Yes all that makes sense.

Will have to invest in some grease and new terminals.

 

[timbobelfast]

If this is a corrosion issue can you try a panel heater with thermostat?

This has saved me in the past with a couple of external panels/ enclosures.

With the fork crimps what about changing to bootlace ferrules?

 

[static zap]

When you mention silver-plated ,I immediately think "Black" !
Air tarnished .
( but does depend on chemicals in the air nearby)

(Do check wiring gauge,as high start-up dissipation may be showing up at the ends )
- or offers more of a thermal sink - for warm terminals -
(temp swap one out for thicker -and compare with neighbours )

 

[Dave OCD]

You could also try ACF50 corrosion block grease or spray, excellent stuff !

 

[GBDamo]

You could also try ACF50 corrosion block grease or spray, excellent stuff !

Already use that stuff on my BMW R1200GS, damn things made out of cream cheese. It is awesome though.

 

[GBDamo]

Leant a few things here, will be replacing loose crimps in future not just squashing them to tighten.

Also think my terminals are tin plated not silver, will double check this.

Also like the idea of checking the cable CS.

Cheers guys.

 

[Dave OCD]

I use it on my bikes too, wonderful stuff.

 

[PEG]

Hi,ignoring any issues regarding corrosion,contamination,etc,most reputable manufacturers,have charts for maximum current limits,with quarter/6.3 receptacles.
I seem to remember Lucar blue 0.25 were about 20 amps,but other brands varied in categorisation.

Some had stamps to show max,some were rated by the maximum wire size accepted,but this was not always in available,standard conductor guages.

There are a great many pieces of workshop type equipment,such as vehicle lifts,compressor welding machines,etc,where similar push connectors just about cope when new,but any damp/corrosion can spell trouble.

 

[dmxtothemax]

Some of these terminals are coated to improve electrical conductivity,
if this coating is worn then conductivity will be reduced
Have you tried just replacing these terminals with good quality one's.

 

[Deleted member 26818]

I use silicon spray grease.