We are doing some remodeling and while moving the thermostat from one wall to another. The wires were shorted against the main copper ground wire in the home. This blew the fuse on the control board. I replaced the fuse but now the blower just runs with or with out the thermostat connected.
This is an older furnace which we had hopes of replacing a couple years down the road. But really would like to squeeze a bit more time out of.
It was working fine before this. I checked everything I could (various reset switches) in the time I had. But did not break out the multi meter. We had a tech come out who confirmed that it was the control board and possibly the transformer.But wanted $300 for parts plus $1000 in labor.
I had to remove the board to change the fuse. Its seven screws and two connections. So I cant see the justification of $1000 in labor to replace that. This was all quoted to my GF as I was at work. When I spoke to the tech he seemed like he just didn't want to fuss with an old furnace in a crawlspace. He said the part was hard to find and that was part of the $1000.

Sucks because I paid him $100 bucks to confirm what I already thought. But I knew that going into it.
I value my time along with others. But for $1000 I am willing to give it a go. My issue is finding a part number for the control Board.

Can anyone point me to a schematic or a part number.

moderator note: Carrier 58 RAV055-111ec

 

Your best bet would be to crawl back in there and get the number off the board. And while you are in there double check the furnace model number on the inside label.

 

That furnace model number should be more like 58RAV070-11112.

The board part number should be listed on the board. It should start with HK42...

It will probably be this one if it isn't the early 1992 or 1993 model..

 

Yeah. Im pretty positive of the model number. But I will head back down and double check it. Along with looking for the number on the board.

 

From the serial number. The furnace is from 1993

 

Do you have a meter ?
Confirm you have 24vac to the board before condemning it.
The transformer may also have gotten blasted.....along with the fuse.

I'll change the title when you confirm the model number.

 

I do not have my meter with me now but can check it in the morning. I am uploading pics of the board and the make/model

 

So the part number is
CES0110057-00

my first look opnline shows it for $474.00 and out of stock

they have a part# CES0110057-02 thats in stock for $165.00

they look pretty similar.
any knowledge on that

I also see from my pics the model# is 58RAV055 ec

 

Might want to check at Amazon, they have a replacement for under a c-buck.

But I second checking the 24 volts....

 

I had worked on a 1985 or older Carrier furnace (model 395AAW048070), the stand up type, to replace the old burned up controller board with a newer micro-processor controller board ($70, model Carrier HH84AA003 HH84AA005 HH84AA009 HH84AA014 HH84AA015).

The fuse blown then fan running non-stop are two safety features of the new board to protect anything possible down the line. The fuse for that new board kept blowing, it suggested a short circuit problem down the line. It was the main gas valve that shorted out. I had the technician do the work because I was afraid of gas leak.

Replacing the board is easy when there's easy access to it. Just label all wires or unplug wires, one at a time to plug in the new, etc.
To check transformer, don't measure voltage in crawl space with power on. Unplug power, use the ohmmeter to check for short/open on primary/secondary sides.

 

So I went ahead and ordered/replaced the board and the transformer. I was able to get a board overnighted with a transformer for $150. As its supposed to get pretty cold this weekend I was worried I wouldn't be able to get the parts.

Downside is that its still doing the same thing. The blower kicks on as soon as the door switch is engaged.
Upside is there is a led code light on the new board.
its giving me a signal for the "limit or flame roll out switch is open".

I checked all the switches I could see but did not find a tripped one. I do have my meter with me and will go check them to see if they need to be replaced.

Any other ideas?
I appreciate all the input and help walking through this.

 

The edge pin connector on that model would draw return air from the unconditioned space and corrode inside.

Looking at the reverse side of the old board might help you see the green terminals better.

Rather than replace the harness you may be able to clean it.

 

Im at work right now so I cant take any shots of the furnace. But when you say edge pin connector are you referencing the plugs that plug onto the side of the board

 

Yes... you have the correct area highlighted.

An open limit switch when the furnace is cold would be a flame rollout switch. There may be one or two and they are near the burner opening. They will have a small pushbutton on them.

 

The plug looks ok inside. i may grab a bit of emery cloth to see if i can clean the connectors a bit. but they don't look to bad.

Both the roll out switches have continuity.

there are two switches on the new board that look to control the blower depending on the switch configuration. I will get a photo as I check continuity on the rest of the limit switches

 

ok So here is a pic of the inside of the board pin plug

Wiring diagram

switches on new board for blower off delay

and this seems to be the only thing inline with the roll out switches.
wondering what it is


Not sure how to proceed here.
doing a bit of research on my end but would love any input.
Thanks again for all the help.

Also
On the limit switches am I looking to have continuity or not.
It would seem that I want it right? Thats the way they are all testing.
The only one I cant quite reach is the one on the system fan/blower.
I can reach the button/pin and it seems to be in the correct position.

 

Yes, you want to read continuity across those limit switches.

Looks like two manual reset and one auto reset switch in that circuit in the diagram.

 

So I seem to have continuity through all the switches. I do not have continuity at PR5 (pressure switch) on the diagram. Should I have continuity through this switch.

 

PR5 is shown as normally open, so you would not have continuity until it's actuated.

 

Pretty much at a loss at this point. Pulled the blower just to check all the switches in back visually even though were getting continuity. Have a tech out now and he's shaking his head also. Might be time for a new furnace. Trying to connect the dots but were still missing something

 

You did double check that you have 24 vac from the transformer like Pete suggested, correct?

 

Yeah we checked that. Ended up taking everthing apart pulling the system motor out. Unplugged the smaller blower motor to check for power. Then plugged it back in and everything fired up.

Tech says he has know idea what he did besides pull it apart a couple times and put it all back together.

Charged me $75 for the service call.

Feels good to have heat.
Thanks everyone for all the help!