I have been having some issues with a 4yr old Carrier 58MVC lately. I was the 4th or 5th tech sent out to a call where the customers 58MVC keeps giving call for service errors. I show up and find many instances of 33- Limit Fault, and 42- Inducer Motor Fault. So I did the usual, take the air flow off of comfort and move it to efficiency, and then enable the low heat rise (it has a bypass humidifier). I adjusted all 3 of the manifold pressures a little lower. Reset all the inducer connections and everything is fine for 2 weeks. Now I get the call back again, and what do you know I'm getting the same errors again, only this time throw in some error 12- Blower on after power up, and medium pressure switch. Now I've personally watched this furnace run for over 3 hours and separate occasions and never once have I witnessed a single error.
I had my temp probe inserted to the limit area, never got above 150*F, limit is 180*F. I had my manometer on the pressure switches, never even got close to the break point. Never witnessed the inducer do anything abnormal.
I called carrier customer support and he was a little puzzled, but he mentioned that error #12 meant there was some sort of power interruption to the furnace. He wants me to install an inline surge protector on the power supply to the furnace. I'm not convinced that will solve anything, and I'm pointing towards a faulty control board, I believe its just giving off phantom error codes randomly.
I locked the furnace in high fire using the Infinity Control and so far haven't had any issues with any error codes.
Anyone else had any issues like this on a Carrier 58MVC?
Code 12 is a normal 90 second blower on after power up.
Code 33 is a limit circuit fault.
Code 42 is a inducer fault.
If the install is 4 years old and the venting isn't undersized then both problems seem unrelated. I agree the control board might be faulty. Has it been replaced in the past? Is the PL4 model plug installed on the control board? It could be the faulty control board fails to energize the inducer fan which could cause the Code 42. It could also fail to energize the main blower fan and cause the Code 33. Control board relay failure.
You can download the 58MVC Series 100 Troubleshooting Guide - Here (http://www.hvactechgroup.com/files/Carrier%2058MVC%20troubleshooting.pdf)
I would also verify the line voltage polarity is okay, and make sure you don't get a reading from the ground wire.
I'm going to first do as Carrier suggests with the surge protector (because why would their control board be faulty - sarcasm) and then I'm going to change the board the 2nd any more errors pop up.
I will report back with the findings.
I had a few similar problems such as this. 4 year old furnace means that the parts are still under warranty and control board is the likely culprit. Check if there is any significant differences between the voltages returning from the sensors back to the board.
Since they suggested something as silly as a surge protector, you could check for things like a floating neutral to confirm there isn't an issue with the main power supply. Turn on their toaster and confirm both legs are holding an equal voltage with give or take 1 or 2 volts. If one goes up while other stays down, they have a neutral issue that could cause intermittent issues with sensitive electronics. Assuming all other connections are good. Check for any bad voltage drops when higher demanding appliances turn on. I've been in a couple houses where the lights dim more than they should when a load is suddenly added. As suggested already, check for any power to ground, there should be none; That's where the power runs to when there's a floating neutral. Not sure how 4 year old carriers do with reverse polarity, I know the ones I've always installed in the last 2 and a half years will throw an immediate code for polarity if it's wrong.
I had a similar fault code 33 on the very same furnace with 80K and what fixed the problem was checking the manifold pressure of both low and high fire as the original installers never bothered to do so .Customer liked to shut all his bsmt supply vents and advised him against it which he took and Problem fixed since
Yeah I did that. Always do. Turned out to be a faulty control board giving phantom error codes.