Carrier SMX ll

[garyde]

I have had problems with one of my SMX ll controls. The temp control does not go up, only down in setting temp. Needs to be replaced.
But in the meantime, I un plugged the contol unit, put it in the freezer for about an hour, and plugged it back in. works well enough to set temp back up to 72.
Transistors and solid state boards like things cold, they operate better.

[merle&louise]

I have had problems with one of my SMX ll controls. The temp control does not go up, only down in setting temp. Needs to be replaced.
But in the meantime, I un plugged the contol unit, put it in the freezer for about an hour, and plugged it back in. works well enough to set temp back up to 72.
Transistors and solid state boards like things cold, they operate better.

Your temp control is kind of like the administration in Washington - spending only goes up not down - it too needs to be replaced!

[merle&louise]

Gary,

I know that you are an electrician so I have a question.

Are you familiar with a product called Dow Corning 4 or DC 4. It is a silicone based grease that is used to displace moisture in electrical connections. I use it on metal haylide light bulb metal bases in my C store canopy.

Do you think it would be safe to use on Printed Circuit Board connections?

[mike kerley]

Tuga,

I've used similar compounds on PC boards without problems. Looking at Dow's sheet "A dimethyl silicone compound, 4 Electrical Insulating Compound lubricates and forms a moisture-proof, electrically-insulating seal for spark plug connections, electrical connections, and electrical assemblies and terminals. Also, it can seal and lubricates cable connectors, battery terminals, rubber door seals, and rubber and plastic O-rings, and can be used as an assembly lubricant in metal-on-plastic and metal-on-rubber combinations", it looks fine and I'd not be concerned.

If your PC contacts are Gold plated, some compounds tend to tarnish them, but connectivity seems to stay high and not creat problem.

Remember that coating the entire board will allow it to more easily gather dirt and particals from the air and could cause a heating issue.

[merle&louise]

Thanks Mike, I think that I will just put a little bit on each female connection then snap them back in.

The reason for my question was once I covered my battery posts with vaseline and that prevented a complete connection.

Thanks again.

[garyde]

I use a 3M product for electrical contacts and such. I don't know about th Dow product. On solid state boards, its usually a specific componant which goes bad, not the entire board. sometimes a solder point will go bad but usually its a transistor or such which has failed.
I have a freind who will fix theses type of things but sometimes you can't get the board apart without breaking something else.

[merle&louise]

I removed my PCB (printed circuit board) today and replaced it with a new one. I was having trouble with the evaporator fan. So I thought this would be a good time to use the DC 4 on the connectors and contacts.

So far no problems, time will tell if it causes any problems.

I spoke to Russ White today and he recommended changing the connectors on the PCB and replacing them with a better grade of connectors. The connectors that are used on these boards are less than stellar. That will be my next project - as soon as I can locate some of the quality connectors.

I think that AC problems are the most feared break-down of all on a coach. That is why I wish I had OTR air!

There's nothing like a backup system - especially when it has 109,000 btu's of cooling power!