Tech Tips From RedDot
Heavy-duty A/C components rarely fail. In fact, the system fails the components because of contaminated refrigerant oil and general lack of preventive maintenance.
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:
1. RECEIVER DRIERS
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.
3. COMPRESSOR/CLUTCH ASSEMBLY
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.
Recommended Pre-Season Maintenance For HYDRONIC Heaters
Before the cold weather arrives, it is recommended that your HYDRONIC 4 / 5 or 10 heaters receive a preseason check. Please use the recommended tools and follow the procedures as outlined in the heater manual while removing and reinstalling the different heater components. Pre‐season maintenance will make sure that your heater(s) are clean, free running and ready for a trouble free season.
The heaters should be inspected and repaired by an Espar trained mechanic, as follows:
1. Check all electrical connections from the heater to the batteries. Check for wear and abrasion along the length of the harnesses. Repair or replace the harness whenever the harness insulation is broken or damaged. Check the battery connections. Clean any corrosion at the terminals. Replace the battery terminals if the corrosion is severe. Check the fuse for corrosion and the correct rating.
2. Check all clamps and hoses. Replace as required.
3. Check the condition of the exhaust system. Check for holes and breaks in the exhaust piping. Replace the exhaust as necessary.
4. Check the fuel pump filter ‐ clean or replace as necessary. For heaters with external fuel pumps, ensure mounting angle of the fuel pump is in between 15‐35o. An incorrectly mounted fuel pump may lead to excessive carbon issues. Check the fuel lines for possible leaks, loose clamps, etc. Once the entire fuel system has been checked and any issues corrected, it is advisable to do a fuel quantity check.
5. Check and clear clogged weep holes on the side of the heater body. Look for any indication of coolant leakages. If leakage is suspected then remove cover with water pump assembly and inspect and replace “O” rings on water pump housing. Closely inspect the heater waterjacket for leakages and replace “O” ring between waterjacket and heat exchanger. If the waterjacket is cracked, replace it.
6. Remove and replace the glow pin screen. Make sure that the new screen is installed correctly as outlined in the repair manual for the heater.
7. Remove and check the glow pin. If it shows signs of dissimilar color or if the glow pin is in any way distorted, replace it.
8. The coolant pump should be removed and the impeller checked for damage. Any dirt or metal particles on the impeller magnet should be removed and the cavity in the pump should also be cleaned. Please Note: coolant pumps are not covered by warranty if the vehicle’s coolant system is excessively contaminated. Refer to Technical Circular 250.
9. Remove the flame tube and check the condition of the flame tube end. The flame tube should be light brown in color with no excessive carbon on the end of the flame tube. Check for carbon build up on the burner “nose” at the cold end of the flame tube. Any carbon covering the air slots should be removed. Check the inside of the heat exchanger and scrape any loose carbon out from between the fins in the heat exchanger. Re‐install the flame tube replacing all gaskets.
10. Re‐assemble the heater and test operation. The heater should be bench tested for 15‐20 minutes before returning the heater to the vehicle.
11. Regardless of the season, run the heater every month for a minimum period of 15 minutes. This will help the heater to burn away any combustion residue in the burner chamber and prevent corrosion in the waterjacket and decay of “O”rings.