Coleman Split Unit Problems

kyallendiy · 11-03-2008, 06:32 PM

I have been going through a few HVAC problems recently. 2 months ago my Circuit board in the unit underneath the house was damaged and had to be replaced. Not cheap, but it was fixed and it ran great till last week. We had the unit on heat, and it had been for at east a week, so it was not the transition. The new Circuit board blew the 5 amp low volt fuse on. I replaced it and it blew it immediately. So I replaced it again, and noticed that before the fuse would blow, the system would buzz for 2 to 3 seconds. So I call a HVAC and they tell me that the board that had ben working properly for 2 months is bad, I'm like hummm.........So I pull the board and began checking everything. The board seems fine so I continue on my quest. I begin hooking th board back up 1 wire at a time and find the culprit to why the fuse is bing blown. When I plug up the 4 pin (wire) connector to the board is when the fuse blows and only then. The only problem, I don't know what these four wire go to? I believe they go to the heater coils??? There are 2 black wires, 1 yellow wire and 1 purple wire in the connector. As said earlier, every wire on the board can be hooked up but as soon as this is connected, bzzz and the fuse blows! HELP ME PLEASE!
Below are some pictures, If anyone can help, I would appreciate, I am just looking for my problem!

biggles · 11-03-2008, 07:07 PM

there is something going on with the control wires into or on the electric heat section check the contactor coils.the limit switch within might be grounded during a call for heat.take your meter in OHMS and read that male boot(that goes into the board boot)to ground might pick up some short

kyallendiy · 11-03-2008, 07:52 PM

I will try that, any other tips or tricks???

simpleman1962 · 11-03-2008, 09:49 PM

I had a problem similar to this on a heat pump and found out that the reversing valve wire was melted and had a dead short to the compressor body. I have ran into this problem since and corrected. The easiest way that I found is to remove one wire at a time on the thermostat and replace fuse as to find out what is blowing the fuse then you will know in which circuit to look at.

**beenthere** · 11-04-2008, 07:41 AM

That connector, is the one that should be hooked up first, not last.
That is where the board gets its line voltage from to operate the blower, transformer, and strip heaters.

If you hooked any wires up before it. Then your test is invalid at identifing where the problem is.