Tag: HVAC Tech Tips

A/C Compressor Check

Wondering why your system has a low refrigerant charge?
It could be because of a leak that needs repair, or a high-side blockage that limits refrigerant flow to the compressor. Diagnose those problems first, and if not resolved, perform this simple 4 step A/C compressor function check, before you remove the compressor from a vehicle. 

Service Tip: Remember when you open the A/C system, you should change your filter drier to remove contaminants and minimize damaging moisture in the system.
AC Compressor - The heart of your air conditioning system.
4 step tech tip
1. Is the compressor rotation smooth? With the vehicle off, turn the compressor shaft with a 14-mm socket. If you feel grinding or hanging as you rotate the shaft, there may be broken components within the compressor. If the rotation is smooth, move on to Step 2.
 
2. Is the coil getting more than 11.5 volts? Take a reading with the engine running and the clutch engaged. If there’s insufficient voltage, get to work on that. Otherwise, move on to Step 3.
 
3. Is the coil resistance between 2.8 and 4.4 ohms for a 12 vdc system and 11.2 to 17.6 ohms for a 24 vdc system? Any resistance outside these ranges will prevent the clutch from engaging or will cause used circuits to open. If the resistance measures correctly, continue to Step 4.
 
4. Is the compressor able to produce 350 psig or more? The compressor should be able to build over 350 psig on the high side with the condenser airflow restricted, and also able to pull the suction side down to 5 psig when the TXV is closed. If needed, the technician can close the TXV by chilling the charge head using a can of dust-off held upside-down.This will temporarily freeze the TVV charge head and cause it to close. If the compressor is operating correctly, the suction pressure will drop below 5 psig.

Need more info. Go to our blog, ATCNEWS or view more tips on the links below
Arctic Traveler Canada has a complete line of replacement parts & HVAC systems for all makes, any HVAC Part or System. Call us today for more information .  

How to inspect an A/C Compressor

Take these steps to inspect an A/C compressor to ensure it really needs replacing before you pull it from a heavy-duty vehicle:

1. Is The Compressor Rotation Smooth?
With the vehicle off, turn the compressor shaft with a 14-mm socket. If you feel grinding or hanging as you rotate the shaft, it’s probably due to broken components within the compressor. If the rotation is smooth, move on to Step 2.

2. Is The Coil Getting More Than 11.5 Volts?
Take a reading with the engine running and the clutch engaged. If there’s insufficient voltage, get to work on that. Otherwise, move on to Step 3.

3. Is The Coil Resistance Between 2.8 And 4.4 Ohms?
Any resistance outside this range will prevent the clutch from engaging or will cause used circuits to open. If the answer is yes, continue to Step 4.

4. Is The Compressor Able To Produce 350 Psig Or More?
If not, leave the compressor where it is. The system may have a low refrigerant charge because of a leak that needs repair, or a high-side blockage that limits refrigerant flow to the compressor.

Tech Tips from Red Dot
” We see lots of compressors that are returned fully functional and therefore not warrantable.
Get the diagnosis right. Inspect an A/C compressor before you pull the component from the vehicle.”


For expert insight into common failures and causes, watch Examining Compressor Failures on ATCTV
While there, check out
How To and Which Components to Inspect and Basic A/C Troubleshooting to further your understanding of A/C Systems.

For more information about AC Compressors or any HVAC component, call the mobile HVAC specialist Arctic Traveler Canada at 800-295-4156.

How to troubleshoot your A/C Electrical system

Tech Tips from Red Dot

On any vehicle and virtually any A/C system, electrical problems are among the hardest to troubleshoot. If you suspect an electrical problem with the A/C system, here’s a two-stage inspection routine that virtually anyone can do with no special tools or skills:

1. Inspect Electrical Connections

As you perform a visual inspection under the hood (cab) and/or at the rooftop condenser, take a moment to check all electrical connections both visually and by feel. Make sure all leads and wires are properly supported and securely connected, and that there’s no corrosion or grime on the leads or connectors.

2. Check Electrical Current Flow and Device Functions

Perform the following steps to check the current flow and electrical device functions:

  • Turn on the ignition. 
  • Turn on the A/C system. This will power the thermostat and clutch. If it does not come on, use the A/C mode switch to check the leads to the switch. You should hear a “click” from the thermostat and hear the clutch drive plate “snap” against the clutch pulley. 
  • Check fuses. If all the connections are clean and tight and there’s still a failure, check the fuses in-cab as well as in-line.
  • Check A/C clutch engagement. Since you can’t see and may not hear the clutch engage, get out and look at the clutch. If it’s engaged, you will see that the drive plate is against the pulley and not slightly spaced from it. If you aren’t sure the clutch is engaged, look for the lead wire connector near the clutch. Break and close that connection. The clutch will disengage and engage again.
  • Test blower speed operation. Some systems have a common switch that turns on the air conditioner and powers the blower motor. Test blower speed operation by adjusting this or the separate blower control switch. Feeling the air flow from the ducts or note blower sound (speed) changes.
  • Inspect roof-mounted condensers. Don’t forget to inspect roof-mounted condensers and A/C units for dirt and debris. Be sure the condenser fan(s) are working properly and all parts and electrical connections are securely fastened. The roof-mounted condenser fans may come on when the system is turned on. Like the thermostat and most clutches, the normal on-off cycling action cannot be observed until the engine is running with the A/C system on.
Once your visual inspection is complete, talk to a qualified A/C technician about what you found. Your troubleshooting efforts will be rewarded with a speedier repair and perhaps a lower repair bill.

Quick Heater Service Tip from Reddot
  • When the status is “heater fan doesn’t work,” check the ground connection for rust, paint, grime, or some other obstruction at the terminus.
  • If the motor doesn’t have a ground wire, its mount serves as a ground connection. Make sure nothing impedes the mount’s ground path.
  • Use a multimeter to make sure you’re getting full voltage to the motor. Once you know the voltage is adequate, you can then look for worn brushes, dirty squirrel-cage fans, damaged fan blades, and other more typical motor problems.

Arctic Traveler Canada
is an MSD/Master Stocking Distributor and Authorized Technical representative for many industry-leading products. Call us today at 1-800-295-4156 to see what 55 years of excellence can do to achieve your business objectives.