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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.
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.