Remove and replace the low-side air conditioning hose on a 1966 Chevrolet Corvette with 327ci V8 engine, including refrigerant recovery and system recharge.

Warnings

Tools required

Parts

• AC low-side hose assembly × 1 — Use OEM specification or AC Delco replacement
• O-ring set for AC fittings × 1 — R-12 compatible o-rings
• R-12 refrigerant × 1 — Per system capacity specification

Preparation

1. Park vehicle on level surface and engage parking brake
2. Allow engine to cool completely if recently operated
3. Verify EPA certification and recovery equipment functionality before beginning
4. Locate low-side service port on AC system (typically on accumulator or suction line near compressor)
5. Inspect entire low-side hose routing from evaporator to compressor for access clearance
6. Have replacement hose, o-rings, and proper refrigerant oil ready before discharging system

Procedure

1. 1

   Connect recovery equipment
   Connect R-12 manifold gauge set to service ports. Blue hose connects to low-side port on the suction line near the compressor inlet. Red hose connects to high-side port on discharge line near compressor. Yellow hose connects to recovery machine. Verify all connections are secure before opening service valves.
2. 2

   Recover refrigerant from system
   Start recovery machine and open both high and low-side manifold valves. Allow machine to run until both gauges read zero or vacuum. This typically takes 15-20 minutes for complete recovery. Close manifold valves and shut off recovery machine. Allow system to sit for 5 minutes and monitor gauges - if pressure rises, residual refrigerant remains and recovery must continue.
3. 3

   Disconnect low-side hose at evaporator
   Locate the low-side suction line connection at the firewall pass-through on the passenger side, where the line exits the evaporator case toward the engine compartment. Using appropriate flare nut wrench, loosen and remove the fitting nut connecting hose to evaporator. Expect small amount of residual oil to drip. Immediately cap evaporator fitting with clean plug to prevent moisture and debris entry. Remove and discard old o-ring from evaporator fitting.
4. 4

   Disconnect low-side hose at compressor
   Trace low-side hose to compressor suction port on driver side of engine. The Harrison A6 compressor has its suction (low-side) port on the rear/side of the compressor body; verify port identification against the factory layout before disconnecting. Using flare nut wrench, loosen and remove fitting nut at compressor inlet. Cap compressor suction port immediately with clean plug. Remove and discard old o-ring.
5. 5

   Remove hose mounting clips
   Follow the low-side hose routing and remove the hose mounting clips (verify exact quantity and locations against factory layout) securing the hose along its run. These are typically spring clips or P-clips secured with screws. Keep hardware for reinstallation.
6. 6

   Remove old low-side hose
   Carefully extract old low-side hose from engine compartment, noting exact routing path, clearances from exhaust manifolds, and relationship to other components. Take photos if needed for reference during installation. Inspect old hose for failure mode - cracks, abrasion, or fitting leaks - to address root cause.
7. 7

   Prepare new hose assembly
   Unpack new low-side hose and verify correct length and fitting types match original. Lubricate new o-rings with small amount of R-12 compatible refrigerant oil (mineral oil, not PAG). Install new o-rings onto evaporator and compressor fittings. Do not over-lubricate - light film only.
8. 8

   Route and install new hose
   Route new low-side hose along original path, maintaining proper clearance from exhaust manifolds (minimum 2 inches) and avoiding sharp bends that could kink hose. Ensure hose does not contact battery, alternator, or moving components like belts and fan.
9. 9

   Connect hose at evaporator
   Remove cap from evaporator outlet fitting. Thread new hose fitting onto evaporator by hand until snug, ensuring o-ring is properly seated. Using flare nut wrench, tighten fitting until firm resistance is felt - typically 1/4 to 1/2 turn past hand-tight. Do not overtighten as this can damage o-ring and create leak.
10. 10

    Connect hose at compressor
    Remove cap from compressor suction port. Thread new hose fitting onto compressor by hand until snug, verifying o-ring seating. Using flare nut wrench, tighten fitting until firm - typically 1/4 to 1/2 turn past hand-tight. Avoid overtightening.
11. 11

    Secure hose with mounting clips
    Install 2 mounting clips at original locations to secure hose to inner fender and frame rail. Ensure hose is not stretched tight or hanging loose - allow slight slack for vibration isolation. Verify hose does not contact any hot or moving components.
12. 12

    Evacuate system
    Connect manifold gauge set to service ports. Connect vacuum pump to yellow hose on manifold set. Open both high and low-side valves and start vacuum pump. Evacuate system for minimum 45 minutes, achieving at least 29 inches Hg vacuum. Close manifold valves, shut off pump, and monitor gauges for 15 minutes - vacuum should hold steady indicating no leaks.
13. 13

    Recharge system with R-12
    With system under vacuum, connect R-12 refrigerant container to manifold yellow hose. Open low-side valve only and charge system to the factory-specified R-12 capacity (verify exact weight in the 1966 Corvette/Harrison service manual before charging). Monitor the gauges - with the engine off and system equalized, static pressure will reflect ambient temperature (typically 70-80 psi at 70-80°F for R-12); operating low-side readings are taken with the engine running. Weigh refrigerant container or use charging scale to ensure accurate charge weight.
14. 14

    Test system operation
    Start engine and set AC controls to maximum cooling with blower on high. Allow compressor to cycle. Monitor manifold gauges: low-side should be 20-30 psi and high-side should be 150-200 psi at idle with 80°F ambient temperature. Inspect all fittings for refrigerant leaks using electronic leak detector or soap solution. Center vent temperature should reach 40-50°F.

Reassembly

1. Verify all hose fittings are secure and leak-free before closing hood
2. Confirm hose routing maintains clearance from hot exhaust components
3. Document refrigerant charge amount and date for future service reference

Verification

• Run AC system for 10 minutes and verify cold air output at vents (40-50°F center vent)
• Check low-side gauge reads 20-30 psi and high-side reads 150-200 psi at idle with system stabilized
• Inspect all connection points for oil residue or frost indicating leaks
• Verify compressor cycles on and off properly with AC demand
• Confirm no abnormal noises from compressor or hose routing interference

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