If you are dealing with a carrier furnace code 13 then we have got you covered. In this troubleshooting guide, we’ll walk you through the possible issues that trigger status code 13 and how to fix each of these issues.
Before you call a tech: MERV 13 is the practical ceiling most home HVAC blowers can run without a problem.
- → Higher MERV = more airflow resistance — a filter your system wasn’t built for can mimic a refrigerant issue.
- → Fiberglass filters clog in ~30 days; a whole-house media filter can go up to 270.
- → The size printed on the box is nominal, not exact — measure your slot if you’re not sure.
A carrier furnace code 13 indicates that the limit switch is open. If the limit switch opens 5 times for at least 3 minutes each time during 1 thermostat cycle this will trigger the status code 13.
This status code is associated with overheating within the furnace causing the limit switch to open. With that said, there are a few things that can cause the high limit switch to open. Let’s look at these issues below.
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Possible Causes of Carrier Furnace code 13
| CAUSE | FIX |
| Blocked return vents or air grillies | Clear anything block return vents or air grillies |
| Misaligned blower wheel | Align blower wheel |
| Defective blower motor | Replace blower motor |
| Bad motor capacitor | Replace capacitor |
| Defective blower control module | Replace blower control module |
| Bad 2 stage furnace control | Replace 2 stage furnace control |
| Defective blower harness | Replace blower harness |
| Excessively clogged air filters | Replace clogged air filters |
Troubleshooting status code 13 on a carrier furnace
Status code 13 on a carrier furnace has to do with restricted air flow around the heat exchangers causing overheating.
If you need to replace the filter, our HVAC Air Filter Buying Guide covers filter types, MERV ratings, and sizing for every system.
To troubleshoot this problem, you may first want to test the limit switch for continuity. If it fails, replace the limit switch. It passes the test, take a look at the air filters and air grilles.
Check for Excessively clogged air filter
Ensure that the air filters are not excessively clogged and that air grilles are not blocked. If they are, try replacing them with clean ones.
If there are no issues with the air filters and registers then let’s go into the blower wheel and motor troubleshooting.
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Testing for a bad blower motor
Start by making sure there is no call for heat on the thermostat then head over to your furnace. Open the blower door.
Keep the door switch tipped in by using a piece of tape. This is to keep the power supply to the furnace on.
Now try setting your thermostat to heat or simply jumper the R wire to the W/W1 terminal and see if the blower kicks on.
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If the blower does kick in after calling for heat and your furnace doesn’t have a variable-speed ICM blower motor, it’s likely that the status code 13 is caused by excessive return-air restriction.
To fix this problem, check the filter and return air grilles for blockage. Add more return-air openings if necessary.
However, if your furnace blower doesn’t run with a call to heat or after jumpering the R and the W/W terminal, turn off the power to the furnace and try to manually spin the blower wheel.
Does the blower spring freely? If not the problem is probably a bad blower motor that will need a replacement to fix the problem.
But in case the blower wheel does spin freely, you may have other components of the blower assembly that are causing the problem and you need to troubleshoot them individually.
These may include a bad blower motor capacitor or blow control module
Solution
If you have a variable speed ICM blower motor, replace the entire ICM blower motor or ICM blower control module attached to the ICM blower motor.
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Testing the blower motor capacitor
A bad blower motor capacitor can also be the reason for a failed motor. A capacitor will store the needed energy to start a motor.
When you have a weak or bad motor capacitor, it wont start the motor. To check whether you have a bad capacitor or not, check for continuity between the following motor leads:
- RED to WHITE
- YELLOW to WHITE
- BROWN to BROWN
- BLUE to WHITE
- BLACK to WHITE
- BROWN to WHITE
If there is continuity to all these leads then it’s time you replace the motor capacitor.
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Final Thoughts
To wrap up, that is all you need to know about carrier furnace code 13. Please see more status codes and how to troubleshoot each of them in this manual.
If you still haven’t figured out what the problem really is or how to fix it, it’s perhaps best to call in a local HVAC tech for help.
Thanks for reading.
