Commercial Upright GN Fridge Troubleshooting: Diagnose Before You Call An Engineer
- 70% DIY-fixable: Blocked condenser, full drip tray, dirty evaporator, misaligned door – staff can fix these in 15 mins.
- Average engineer call-out: £180–£280 + parts. Prevention saves £2,000–£5,000 per fridge per year.
- Fridge lifespan: 10–15 years (Foster, Williams); 8–12 years (Gram, True). Maintenance adds 3–4 years.
- F-Gas compliance: Any work involving refrigerant or sealed system requires certified engineer (EU 517/2014).
- Defrost cycle: Runs typically 2–4 times per 24h; blocks flow for 15–20 mins. Not a fault.
- Climate class: Upright GN must match location. Spec: T (16–22°C). Wrong class = 50% more runtime, 30% shorter lifespan.
- PAT testing: Annual UK requirement (EAW 1989). Cost ~£20 per unit. Tags must be visible; insurance void if missing.
- Common cause rank: 1. Blocked condenser (40% faults). 2. Door seal failure (25%). 3. Refrigerant low (15%). 4. Thermostat drift (10%). 5. Electrical (10%).
- 1. Fridge Not Cooling / Temperature Drifting Up
- 2. Frost or Ice Build-up Inside Cabinet
- 3. Compressor Running 100% / Not Cycling
- 4. Strange Noises (Grinding, Rattle, Hum)
- 5. Water on Floor / Drip Tray Overflowing
- 6. Door Won’t Seal / Hinge Sagging
- 7. Display Error Code (Foster, Williams, Gram, True, Polar, Inomak)
- 8. Strange Smell from Fridge (Biofilm, Mildew)
- Safety & F-Gas Compliance Checklist
- Multi-Brand Error Code Reference
- Repair vs Replace Decision Matrix
- Frequently Asked Questions
1. Fridge Not Cooling / Temperature Drifting Up
What it looks like: Fridge is warmer than it should be (set to 2–4°C but reading 8°C+). Temperature climbs slowly over hours. Compressor might be running constantly. Food at risk.
Feel the back and underside of the fridge. Is the condenser coil covered in dust, cobwebs, or grease? Blocked airflow kills cooling. Clean with a soft brush or compressed air. Clean every 2 months in busy kitchens. Expected fix time: 10 minutes. Success rate: 65%.
Close the door on a piece of paper. Can you pull it out easily? Bad seal = cold air escapes. Feel for warm air leaking around the door. Check that nothing is blocking the door from closing fully (ice, food packaging). If the seal is cracked or peeling, replacement cost is £40–£80 and takes 20 minutes. Success rate: 25%.
If frost builds on the evaporator fins (you may see ice on the back wall inside), the defrost drain may be blocked. Pour warm water down the drain hole (usually at the bottom-back corner of the cabinet, inside). Listen for it to flow freely. If it’s gurgling or backing up, it’s likely blocked. A blocked drain causes 20% of cooling issues.
Upright GN fridges rated for climate class T operate at 16–22°C ambient. If your kitchen is 28°C (near a pass, summer heat, bad ventilation), the fridge has to work 50% harder and will struggle to hold 2°C. Check your fridge’s data label for climate class. If it doesn’t match, call an engineer; you may need a different model or better kitchen ventilation. Success rate if wrong: 100% (requires hardware change).
STOP HERE. Refrigerant loss is F-Gas regulated. You must call a certified engineer. Do not attempt to refill. Cost: £250–£400 + diagnosis. Time: 1–2 hours. If the fridge is over 10 years old and has lost gas, replacement may be cheaper than repair (new unit ~£1,800–£3,200).
2. Frost or Ice Build-up Inside Cabinet
What it looks like: Thick frost on the evaporator coil (back or side wall inside cabinet), or ice forming on shelves. Air vents partially blocked by ice. Temperature may drop too low or fluctuate.
Upright GN fridges defrost 2–4 times per day, typically at night or after heavy use. During defrost, the evaporator heats briefly to melt frost. This is automatic and takes 15–20 minutes. If you see frost only during night hours or after closing time, it’s not a fault. If frost is constant and blocking air vents, move to step 2.
Ice build-up inside usually means the defrost water is not draining away. Find the drain line at the base of the fridge (back corner, often plastic tube). Is it clear or blocked? Pour warm water down it. Listen for free flow. If no water comes out, the drain is blocked by ice, algae, or food debris. Use a thin wire or pipe cleaner to clear it. Success rate: 55%.
Every time the door opens, warm, humid air enters. The evaporator then cools that air, and the moisture condenses and freezes. If staff are opening the door very frequently or not closing it fully, frost accumulates faster. Teach staff to minimize door openings and check the seal (see Symptom 1, Step 2).
If the defrost cycle is not triggering, frost will build continuously. This requires a multimeter and circuit knowledge. Not recommended for untrained staff. Call an engineer. Cost: £150–£250 for diagnosis + repair.
If frost is blocking airflow and you need the fridge running NOW: switch the fridge off, let it sit at room temp for 2–4 hours, drain the meltwater into a bucket at the base. Wipe the coil dry. Switch back on. This is emergency-only. The fault will return unless you fix the underlying drain blockage (see Step 2).
3. Compressor Running 100% / Not Cycling Off
What it looks like: Compressor (the motor/pump unit, typically at the back bottom) is running constantly without stopping. It cycles on and off normally for 5–15 minute intervals. If it never stops, something is wrong.
If the compressor is running constantly AND the fridge is holding 2–4°C correctly, you have a hunting issue (compressor cycles very quickly). Check the condenser is clean (see Symptom 1, Step 1). If condenser is clean and the temp is right, contact the maker – this may be thermostat drift or a control board issue. If the compressor is running constantly and the fridge is WARM, move to Step 2.
If the compressor runs continuously but the fridge is not reaching or holding the target temperature, the sealed system has lost gas (leak or original charge loss). This requires a certified engineer under F-Gas regulations (EU 517/2014). Do not attempt to top up refrigerant yourself. Cost: £250–£400. If the fridge is near end of life, replacement may be better value.
If your kitchen is hotter than the fridge’s rated climate class (e.g., Class T rated fridge in a 30°C kitchen), the compressor will run constantly trying to cool down. This is not a fault, it’s a specification mismatch. Improve kitchen ventilation or move the fridge, or spec a Class N or K fridge for hotter kitchens next time.
Is the fridge next to a pass, oven, or hot plate? Direct radiant heat makes the compressor work overtime. Reposition if possible, or install a thermal shield. Move food prep heat sources at least 1 metre away.
4. Strange Noises (Grinding, Rattle, Hum, Buzzing)
What it looks like: Compressor makes a grinding, screaming, or squealing sound. Or a rattle from inside the cabinet. Or a high-pitched buzzing or hum that wasn’t there before.
Compressor (back of fridge, bottom): grinding, squealing, high-pitched whine. Fan (evaporator or condenser): rattle, buzz, hum. Listen carefully. If you can’t tell, record a video and send it to your supplier or engineer. Success rate of identifying via sound: 70%.
Grinding or squealing from the compressor usually means the bearing is worn. This is a slow leak that will worsen. The compressor will eventually seize. Cost to replace the compressor: £350–£650 + labour (2–3 hours). If the fridge is over 10 years old, this is a sign to plan replacement.
The compressor sits on rubber/spring mounts that absorb vibration. If these fail, the compressor will rattle against the frame. Check if the fridge is level (use a spirit level). If it’s tilted, it stresses the mounts. Adjust the fridge feet to level it. Cost: free. Success rate: 20%.
Condenser fan: sounds like a card in bicycle spokes. Evaporator fan: hum with a rattle. Check if ice is blocking the fan (if fridge has been too cold or frost has formed). Listen for the fan hitting something. If the fan blade is cracked or loose, it needs replacement. Cost: £80–£150 + labour.
If you hear a high-frequency hissing or whistle from the refrigerant lines (copper tubing), this can indicate high-pressure gas escaping or a restriction in the line. This requires a certified engineer. Cost: £200–£300 + repair.
5. Water on Floor / Drip Tray Overflowing
What it looks like: Puddles forming under the fridge or drip tray at the base is full to overflowing. Water trickling down the side of the cabinet or pooling at the front feet.
Open or pull out the drip tray at the base (usually slides out). Is it full of water? This is normal if the fridge has been running heavily, especially in hot weather or if many door openings occur. Empty the tray. It should have a small drain hole at the back or side. Pour water down that hole to test drainage. Does it flow freely? If water sits in the tray, the drain is blocked. Success rate: 30% (often just needs emptying).
This is the same issue as in Symptom 1 (cooling loss). The water that should drain from the evaporator (where defrost happens) is backing up. It may overflow inside the cabinet, or seep out the base of the fridge, or into the drip tray faster than the tray can handle. Clear the drain using warm water, a wire, or a small suction pump. Success rate: 50%.
Some commercial fridges have a small pump at the base that pushes condensate water out to a waste line instead of a tray. If this pump fails, water backs up and leaks. Listen for the pump running (small electric hum, usually when the defrost cycle runs). If silent and there’s water pooling, the pump may be dead. Cost to replace pump: £80–£120 + labour.
If the door seal is weak, humid kitchen air enters continuously. The evaporator condenses this humidity, producing more water than normal. Test the seal (paper pull test, see Symptom 1, Step 2). A new seal: £40–£80.
Use a spirit level to check if the fridge is tilted. It should drain towards the back. If tilted towards the front or sides, water will pool at the front feet. Adjust the fridge feet (usually screw-adjustable at the base) to ensure a slight slope towards the back. Success rate: 10% (rare to be the only cause).
6. Door Won’t Seal / Hinge Sagging
What it looks like: Door is visibly misaligned. It doesn’t close flush. You can see light around the door frame. Air leaks from the bottom or top corner. Hinge feels loose or squeaks.
Feel the rubber seal all the way around the door. Is it cracked, peeling, hard, or compressed? Gaskets last 5–8 years on average. Cost to replace: £40–£80. Installation: 20 minutes. Do this first because a bad seal causes 25% of all fridge faults (cooling loss, compressor overrun, water inside). Success rate: 95% (if the gasket is the issue).
Look at the hinge screws (usually on the side of the door where it attaches to the fridge). Are they tight? Try tightening them with a wrench or screwdriver. Over-tightening can strip threads, so be gentle. If a screw is broken or missing, you may need a replacement hinge. Cost: £20–£40 per hinge.
Some commercial fridges have adjustable hinge pins or tension screws that let you raise the door. Check the top hinge for a small screw or clip. If you can adjust it, do so in small increments (quarter turns) until the door aligns. If there’s no adjustment, the hinge may be permanently bent. Replacement cost: £50–£100 + labour.
Uneven flooring can cause door misalignment. Use a spirit level on the top of the fridge. If tilted, adjust the feet. Often the levelling feet are at the front and adjustable with a wrench. This can solve a door seal issue without replacing anything. Success rate: 15%.
If the hinge is truly bent, the door may need to be removed, the hinge straightened (usually not possible – requires replacement), and the door rehung. This is a 1–2 hour job. Call an engineer. Cost: £150–£250.
7. Display Error Code (Foster EcoPro G2, Williams Jade, Gram K, True T-49, Polar U-series, Inomak)
What it looks like: A code appears on the digital display (e.g., “E1”, “F1”, “C3”, “Err5”). The fridge may stop cooling, alarm, or operate in a reduced-capacity mode.
Error codes are brand-specific. Below is a multi-brand reference:
| Brand | Code | Meaning | DIY Fix? | Est. Cost |
|---|---|---|---|---|
| Foster EcoPro G2 | E1 | Evaporator sensor fault (temperature probe) | No | £140–180 |
| E2 | Condenser sensor fault | No | £140–180 | |
| E3 | Control board failure | No | £300–450 | |
| E4 | Defrost thermostat open circuit | No | £120–160 | |
| Williams Jade | F1 | High-pressure switch triggered (refrigerant overcharge or blockage) | No | £180–280 |
| F2 | Condenser fan motor failed | No | £100–150 | |
| F3 | Temperature sensor short | No | £130–170 | |
| F4 | Low-pressure switch triggered (refrigerant leak) | No | £200–350 | |
| Gram K | C1 | Compressor protection thermal overload | Yes* | £0–20 |
| C2 | Condenser blockage or ambient too high | Yes | £0–40 | |
| C3 | Evaporator sensor open circuit | No | £120–150 | |
| C4 | Compressor relay stuck | No | £110–140 | |
| True T-49 | Err1 | Freezer sensor malfunction (may show in upright mode if integrated) | No | £160–200 |
| Err2 | Refrigerator sensor malfunction | No | £160–200 | |
| Err3 | Control board communication failure | No | £280–400 | |
| Polar U-series | AL1 | High temperature alarm (fridge warming) | Yes* | £0–180 |
| AL2 | Door open alarm | Yes | £0–80 | |
| AL3 | Sensor fault | No | £130–170 | |
| Inomak | E001 | Probe sensor disconnected or shorted | No | £110–150 |
| E002 | Compressor overtemperature protection triggered | Yes* | £0–50 | |
| E003 | Evaporator sensor fault | No | £120–150 |
* = Try this before calling an engineer:
- Gram C1 (compressor overload): The fridge may have shut down due to overheating (blocked condenser, high ambient temp, or low refrigerant). Clean the condenser (see Symptom 1, Step 1). Wait 30 minutes. Power cycle the fridge. If the code clears, you’ve fixed it.
- Gram C2 (condenser blockage): Clean the condenser immediately. Check the ambient temperature. If above 25°C and the fridge is in a Class T spec (16–22°C), the kitchen is too warm.
- Polar AL1 (high temperature alarm): The fridge has warmed above the alarm threshold (usually 6–8°C). Check condenser blockage, door seal, and evaporator drain (see Symptom 1). This is often fixable.
- Polar AL2 (door open alarm): The door has been open too long or the door sensor is misaligned. Close the door fully. Ensure nothing is blocking it. If the alarm persists, the door sensor may need adjustment or replacement (£50–£100).
- Inomak E002 (compressor overtemp): Same as Gram C1. Clean condenser and wait 30 minutes.
If the code doesn’t clear after these steps, call an engineer with the code number, your fridge model, and serial number (on a label at the back).
8. Strange Smell from Fridge (Biofilm, Mildew, Rotten Food)
What it looks like: An unpleasant odour coming from the fridge – musty, sour, or ammonia-like. Often concentrated near the evaporator or drain area.
Open every shelf and corner. Remove any items past their use-by date. Check the drip tray – old, stagnant water breeds bacteria fast. Empty and clean the tray with hot soapy water. Smell should improve immediately if food was the culprit. Success rate: 40%.
The drain line at the base of the fridge collects moisture, algae, and food particles. This creates a biofilm that smells like mildew or stagnant water. Use a small suction pump or turkey baster to flush warm, soapy water down the drain hole. Repeat several times. Follow with plain water. This is the same drain as in Symptom 1 and Symptom 5. Success rate: 70%.
On some upright GN fridges, you can access the evaporator (a set of metal fins inside the fridge, usually on the back or side wall). If you see visible mould or algae growth on the coil, turn off the fridge, let it thaw, and wipe the coil with a cloth dampened in dilute bleach (1 part bleach to 10 parts water). Wear gloves. Rinse thoroughly with clean water. Do not allow bleach to drip into the drain. Success rate: 60%.
Occasionally, a insect, rodent, or debris gets into the condenser fan area at the back of the fridge. This decays and smells foul. Check the area behind and underneath the fridge. Remove any obvious debris. If you suspect a dead animal, call an engineer; they have better access.
Flush the evaporator drain with warm water once a month. This keeps biofilm from building up. Cost: 10 minutes and a jug of hot water. This is the single best way to avoid smell complaints in upright GN fridges.
Safety and F-Gas Compliance Checklist
- F-Gas Certification (EU 517/2014): If you or your team open the sealed system, you must hold Category I (for systems containing more than 40 tonnes CO2 equivalent) or Category II certification from a Notified Body (e.g., REAL Qualifications, CoolCare). Always use a certified engineer if in doubt. More info: UK legislation: EU 517/2014 retained.
- PAT Testing (EAW 1989): Commercial catering equipment must be PAT tested annually. The fridge should display a tag showing the last test date and engineer signature. If no tag or tag is over 12 months old, arrange testing immediately. Cost: ~£20 per unit. Failure to maintain records can invalidate insurance and breach HSE requirements. More info: Equipment at Work Regulations 1989.
- Temperature Monitoring (EC 852/2004): Your fridge must maintain food at 0–4°C. You must have a way to verify this daily. Keep a temperature log (simple pen-and-paper record of fridge reading each morning). If the fridge fails and food warms to 15°C+, you have a food safety incident and must notify enforcement. More info: EC 852/2004 retained.
- Electrical Safety: Do not attempt electrical repairs (e.g., replacing the compressor capacitor or contactor relay) unless you are a qualified electrician. Capacitors store high voltage and can cause serious injury or death if mishandled. Call an engineer. More info: BS EN IEC 60335-2-89 Commercial Refrigeration.
- Thermal Testing (EN ISO 22041): If the fridge fails to hold temperature consistently (drifts by more than 2°C), have an engineer test the insulation and sealing integrity. A fridge with poor insulation will fail increasingly often and should be replaced rather than repeatedly repaired.
- WEEE Compliance (Waste Electrical & Electronic Equipment): When your fridge reaches end of life, it must be disposed of according to WEEE Directive 2013/56/EU (UK retained law). Do not put it in general waste. Contact a licensed WEEE recycler. More info: WEEE Regulations 2013.
- Staff Training: Document that staff have been trained on: (a) door sealing and closing, (b) drip tray emptying, (c) condenser cleaning, (d) daily temperature checks, (e) reporting faults promptly. Keep training records for HSE compliance.
- Spill Kit: Keep a refrigerant spill kit near the fridge in case of leaks (absorbent granules, gloves, waste bags, spill notice). If the compressor leaks, do not attempt to contain it; evacuate, ventilate, and call the engineer immediately.
Multi-Brand Error Code Reference (Summary Table)
For quick lookup when a code appears. See the detailed table in Symptom 7 above for remedies.
| Brand | Code | Likely Cause | DIY Possible? |
|---|---|---|---|
| Foster EcoPro | E1–E4 | Sensor faults, control board issues | No |
| Williams Jade | F1–F4 | Pressure switch, fan, sensor, refrigerant | No |
| Gram K | C1–C4 | Compressor, condenser, sensor, relay | C1, C2: Yes; C3, C4: No |
| True T-49 | Err1–Err3 | Sensor malfunction, control board | No |
| Polar U-series | AL1–AL3 | Temperature, door, sensor | AL1, AL2: Maybe; AL3: No |
| Inomak | E001–E003 | Probe, compressor temp, evaporator | E002: Maybe; E001, E003: No |
Repair vs Replace Decision Matrix
Should you fix the fridge or buy a new one? Use this table to decide.
| Fridge Age | Repair Cost | Recommended Action | Notes |
|---|---|---|---|
| 0–3 years | Up to £300 | Repair | Still under extended warranty in most cases. Repair is economical. |
| 0–3 years | £300–£600 | Repair | Still should be reliable. Repair is justified. |
| 0–3 years | £600+ | Replace if compressor or control board | Major components nearing cost of a new fridge. Consider upgrade. |
| 3–8 years | Up to £250 | Repair | Good ROI. Fridge will likely serve 4–6 more years. |
| 3–8 years | £250–£500 | Repair | Monitor closely. If it fails again within 12 months, replace. |
| 3–8 years | £500+ | Replace | Compressor, sealed system, or control board replacement. Buy new. |
| 8–12 years | Up to £200 | Repair | If it’s a minor seal or fan, repair. Check fridge’s reliability history. |
| 8–12 years | £200–£400 | Replace | Fridge is nearing end of design life (12 years typical). Budget for new unit. |
| 8–12 years | £400+ | Replace | Definitely buy new. Cost to repair is approaching cost of new. |
| 12+ years | Any amount | Replace | Fridge has passed typical lifespan. Replacement cost will be recovered in reliability and energy savings within 3–4 years. |
Related Guides
Most upright GN fridge faults (70%) can be fixed by kitchen staff in under 30 minutes: clean the condenser, empty the drip tray, clear the evaporator drain, or replace a door gasket. Temperature loss, frost buildup, water leaks, and noises often trace to a blocked drain or dirty condenser. If an error code appears, check multi-brand reference above—Gram C1/C2 and Polar AL1/AL2 may be fixable; most other codes need an engineer. Refrigerant loss, compressor failure, and electrical faults require certification (F-Gas, electrician). Annual PAT testing is mandatory (£20, UK law). A 10-year-old fridge with major faults (compressor, sealed system) should be replaced, not repaired—new upright GN fridges cost £1,800–£3,500 and save ~£1,000/year in energy. Keep detailed temperature logs and temperature monitoring to comply with EC 852/2004 food safety regulation.
