Tech tip courtesy of RedDOTHow to increase defroster performance and visibility for drivers ? Do a wintertime PM on your A/C system!
Ensure your A/C system runs at optimal performance all year by including a complete HVAC inspection before winter.
One of the best ways to improve uptime and reduce maintenance costs for the customer is to promote a basic visual check of major A/C components, hose connections, and fittings at regular intervals, like with every engine-oil change. This inspection routine has another benefit: it can generate business for your parts and service department.
Many A/C components are consumable items. It’s more cost-effective to replace them than to repair them. So preventive maintenance is an opportunity to sell a range of OEM-quality all-makes replacement parts for the air conditioner. Here are some examples:
The receiver-drier’s moisture indicator provides a quick visual cue about the refrigerant’s condition: a blue dot means the refrigerant is dry; pink, white, or grey indicates acid or moisture in the system. Checking the sight glass during an oil change or any scheduled maintenance procedure means the truck can receive necessary service while it’s there in the shop, before moisture and acid damage critical A/C components and lead to a failure on the road.
Dust, bugs, feathers, and other debris collect on the face of fins and tubes and act as a thermal barrier, making it hard for the condenser to shed heat. Condensers also fail because of vibration, which can cause hose connections to come loose and fatigue the condenser tubing adjacent to the fittings. Every 12 months, the condenser should be cleaned (taking special care not to bend or damage the fins) and the hose connections securely clamped.
The compressor provides the mechanical energy to circulate refrigerant and manipulate the pressure inside the system. It’s the heart of the A/C system, and the No. 1 HVAC maintenance expense item. Excessive noise and poor cooling performance are the two most obvious symptoms that a compressor is failing. Replacing the compressor involves pulling down the system, which adds refrigerant recovery and recharge to the repair cost.
Next time you see, “A/C won’t blow cold air” on a work order, note that the repair and downtime probably could have been avoided with a simple visual inspection of the truck’s air conditioning system. Any time you change the truck’s oil, check the A/C.
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. Perform a simple compressor function check before you pull the component from the vehicle.”
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 current flow and electrical device functions:
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.
A relatively new feature in the heavy duty industry, the cabin air filter is often overlooked in regular vehicle maintenance. That’s unfortunate because the cabin air filter is just as important to the passengers as the engine air filter is to the vehicle and a likely cause of “A/C Not Blowing Cold“. A cabin filter processes the air that enters the passenger compartment via the vehicle’s heating and air conditioning system, increasing passenger comfort by trapping particulates, pollen, and other irritants.
For people with allergies and other sensitivities to airborne agents, the cabin filter represents a significant advance. Replacing the cabin air filter at the recommended interval, or sooner especially in areas of high particulate, allows the A/C system to run at optimal efficiency and passengers to breathe cleaner, fresher air, which makes any journey more enjoyable – Courtesy of Denso Corporation