Tempstar Furnace not heating / not cooling in Greater Vancouver
There is an order to this, and it is not the order most people use. Homeowners tend to jump straight to the furnace. Technicians start further back, because roughly half of no-heat calls end at the thermostat, the breaker, the filter, or a service switch someone flipped while moving boxes.
The other thing worth knowing up front: your furnace blower is also your air conditioner’s blower. If the furnace will not run, the outdoor unit can hum along all afternoon and you will still get nothing at the registers. So “not cooling” and “not heating” frequently share one root cause.
What follows is the sequence we actually work through on a Tempstar gas furnace across Metro Vancouver and the Fraser Valley, with the reasoning behind each step, and a clear line marking where a homeowner should stop and a TSBC-certified technician should take over.
Confirm the call for heat is actually reaching the furnace
Before touching the furnace, prove the thermostat is asking for heat. Set it to Heat, then push the setpoint at least five degrees above room temperature and wait a full minute. Furnaces have built-in delays, and plenty of “it does nothing” calls are someone giving up after fifteen seconds.
Check the basics that hide in plain sight. A thermostat in Cool with the outdoor temperature at four degrees will do nothing useful. A programmable schedule someone set in September can hold a setback all evening. Batteries in a battery-powered thermostat die quietly and take the display with them. Smart thermostats can lose their connection to the equipment after a firmware update or a power blip.
The more useful test is whether the furnace responds at all. Switch the thermostat fan setting from Auto to On. If the blower starts, low-voltage control power is present and reaching the furnace, and your problem is on the heating side. If nothing happens at all, you likely have no power or no control voltage, and that reframes everything.
Also check that the thermostat is not being fooled. A lamp, a supply register blowing on it, or sun off a window can make the thermostat believe the room is already warm. In older homes with a thermostat on an exterior wall, drafts do the opposite.
Power, the door switch, and the service disconnect
Three things kill power to a furnace, and all three are free to check.
First, the breaker. Find the furnace circuit in the panel and look carefully, because a tripped breaker often sits in a middle position rather than fully off. Push it firmly to Off, then back to On. If it trips again right away, stop. A breaker that trips repeatedly is telling you about a short or a failing motor, and repeatedly resetting it is how a nuisance becomes a fire risk.
Second, the service switch. It looks exactly like a light switch, usually mounted on or beside the furnace or at the top of the basement stairs. It gets switched off by painters, movers, and anyone who assumed it was a light. We have driven to no-heat calls in Burnaby and Coquitlam that ended with flipping that switch.
Third, the blower door safety switch. Tempstar furnaces, like every modern gas furnace, will not run with the blower compartment door off. The door has to be seated properly and latched for the plunger to depress. If someone changed a filter and did not reseat the panel, the furnace is dead by design.
With power confirmed, look for the small viewing window on the front of the furnace. A steady or flashing light means the control board is alive and has something to tell you.
Read the fault code off your own unit, not off the internet
Almost every modern Tempstar furnace flashes a diagnostic pattern through a small window on the blower door. Count it carefully: how many flashes, the pause between groups, and whether the colour changes. Photograph it or take a short video, because patterns repeat and it is easy to miscount from memory.
Now the important part. Do not look up the meaning on a random forum. Fault code meanings vary by brand, by model, and by production year, and Tempstar has used more than one diagnostic scheme over the decades. The authoritative source is the label inside your furnace’s blower door, or the installation manual for your exact model number. That model number is on the rating plate inside the cabinet.
What the code gives you is a category, not a part. Broad categories you will encounter include ignition failure, flame sense failure, pressure or venting faults, limit and overheat trips, flame present when it should not be, and internal control faults. Each of those has multiple possible causes, which is exactly why a code is a starting point rather than a diagnosis.
Give the code to whoever you call. A technician who knows before arrival that the board is reporting a pressure switch category will bring a manometer and check venting and condensate first, instead of working outward from nothing. It genuinely shortens the visit.
Furnace runs then blows cold: flame proving and lockout
This is one of the most common patterns we see. The furnace fires up, you feel warm air briefly, then it goes cold and shuts down. After a few attempts the furnace stops trying entirely.
What is happening is that the flame started but the control did not stay satisfied that it was there. Modern furnaces use a flame sensing rod sitting in the burner flame, and the control expects a tiny electrical current through that flame. No current, no proof of flame, and the gas valve closes within seconds as a safety response. After a set number of failed attempts, the board locks out.
Causes cluster in a few areas. A flame sensor coated with oxide film after years of service loses its signal. A poor ground at the furnace chassis breaks the circuit the sensor relies on. Weak or lifting flames from partially blocked burner ports move the flame off the rod. Marginal gas pressure produces the same result.
The pattern is recognisable: consistent, repeatable, and it usually gets worse gradually over a season rather than failing overnight.
This is not a homeowner repair. The sensor sits inside the burner compartment on a live gas appliance, and cleaning it wrong or reinstalling it slightly out of position causes exactly the failure you were trying to fix. Cycling power to clear the lockout over and over just repeats the unsafe sequence.
Venting, condensate and pressure switch faults on the coast
Before a Tempstar furnace lights, it proves it can vent. The inducer motor starts, pulls a draft, and a pressure switch confirms that draft exists. If the switch does not close, the sequence stops. No ignition, no heat, no blower.
On the coast this fault has some very local causes. High-efficiency furnaces vent through plastic pipe out a sidewall, often low to the ground. Leaves, garden debris, drifted snow, a rain-driven pool of water in a poorly sloped run, or a bird nest can all restrict it. We have cleared vent terminations in Langley and Maple Ridge that were half-buried by landscaping added the previous summer.
Condensing furnaces also produce acidic condensate that must drain continuously. A blocked trap or a drain line that has developed a sag full of water will back pressure into the vent path and trip the switch. Damp mechanical rooms and long horizontal drain runs make this common here.
Other causes include a cracked or disconnected pressure tube, water sitting in the tube, or a failing inducer motor that spins but no longer generates enough draft.
What you can safely do: walk outside and physically look at the vent termination and intake, and clear anything blocking them by hand. Everything past that, including tubing, the trap and the switch itself, is technician work on a combustion system.
Short cycling, overheating and the limit switch
A furnace that runs for a few minutes, shuts down, then restarts a few minutes later is usually overheating, and overheating is almost always an airflow problem.
The high limit switch exists to shut off the burners if the heat exchanger gets too hot. It is doing its job. What it is telling you is that not enough air is moving across the exchanger to carry heat away. Chase the airflow, not the switch.
Go in this order. Filter first, because a loaded filter is the single most common cause and the cheapest to rule out. Then registers: closed supply vents, especially several of them, choke the system. Then returns: furniture against a return grille, or a return blocked by storage in a utility room. Then the blower itself, where a wheel caked with years of dust moves far less air than it should even at full speed. Then ductwork, particularly crushed flex duct in a crawlspace or an undersized return added during a basement renovation.
Repeated overheating cycles are hard on a heat exchanger, which is the component you least want damaged, because a compromised exchanger is a combustion safety issue rather than a comfort one.
If your furnace short cycles and you have already changed the filter and opened everything, stop guessing and get it measured. Static pressure readings tell the story in minutes.
Not cooling: why the furnace is usually the reason
In a typical Metro Vancouver home with central air or an add-on heat pump, the indoor coil sits on top of the furnace and the furnace blower moves the air. So when nothing comes out of the registers on a hot day, the furnace is a prime suspect, not an innocent bystander.
Work it the same way. Set the thermostat fan to On. If the blower runs, the furnace’s air-moving side is functional and the problem lies with the outdoor unit, the refrigerant circuit, or the cooling call. If the blower does not run, everything in the previous sections applies: breaker, service switch, blower door, control board, blower motor.
A second common pattern is a system that cools weakly then quits. That often traces to a frozen indoor coil, which itself is usually caused by restricted airflow, a clogged filter being the classic, or by a refrigerant issue. Ice on the coil blocks air completely. Turn the system off, run the fan only to thaw it, replace the filter, and if it freezes again, it needs a technician.
Coastal homes near the water get one extra factor: salt air accelerates corrosion on outdoor coils and cabinets. A coil that looks fine from three metres away can be significantly degraded up close, which shows as poor capacity long before it shows as a total failure.
What to do before the technician arrives, and what it will cost
Do these five things and you shorten the visit. Change the filter and note the date. Photograph the fault code pattern. Write down the sequence: what starts, what does not, how long before it quits. Confirm the gas is on if you have other gas appliances to test with, such as a range or fireplace. Clear a working path to the furnace, including moving storage away from the blower door.
On cost, we will not quote a number on a web page, because it would be fiction. What actually drives the price of a no-heat repair is the failed component, whether the part is current or obsolete for your model year, access difficulty, whether the fault has damaged anything downstream, and whether the unit is old enough that repair versus replacement becomes a genuine question. HeatLand provides a free written, no-obligation estimate after diagnosis, so you see the scope before anything is authorized.
If efficiency comes up while you are weighing repair against replacement, ask for the AFUE rating from the manufacturer’s spec sheet or the AHRI listing for the exact model being proposed, rather than accepting a general figure. Rebate programs through CleanBC and FortisBC change their terms periodically, so confirm current eligibility directly with the program.
And the safety line does not move. Gas smell or CO alarm means leave the home and call the gas utility and a licensed technician from outside. HeatLand: (604) 330-3812, serving Metro Vancouver and the Fraser Valley since 1999.
Quick Checklist
- Set the thermostat to Heat and raise the setpoint at least five degrees, then wait a full minute
- Switch the fan from Auto to On to confirm the blower and control power respond
- Check the furnace breaker, the wall service switch, and that the blower door is latched
- Photograph the control board’s flashing code and read it against your own unit’s label or manual
- Replace the filter and open every supply register and return grille
- Walk outside and clear leaves, snow or debris from the vent and intake terminations
- Confirm other gas appliances work, which tells you gas supply is present
- Stop and call a technician for burner, gas valve, flame sensor, pressure switch or control board work
| Symptom | Most likely area | Your next step |
|---|---|---|
| Nothing happens at all | Power, service switch or blower door | Check breaker, wall switch, and that the door is seated and latched |
| Blower runs but air is cold | Ignition or flame proving | Photograph the fault code and book a technician; do not repeatedly reset |
| Fires briefly then shuts down repeatedly | Flame sense or lockout | Note how many attempts before lockout and call for service |
| Runs then shuts off, restarts minutes later | Airflow and high limit | Replace the filter, open all registers and returns, then have static pressure measured |
| Inducer runs but never ignites | Venting, condensate or pressure switch | Inspect and clear the outdoor vent termination, then call for service |
| No cooling, no air at registers | Furnace blower side | Set fan to On; if the blower does not run, treat it as a furnace fault |
Frequently Asked Questions
My Tempstar furnace tries to start three times then quits. What is that?
That is a lockout. The control attempted ignition, failed to confirm a stable flame each time, and shut down to stay safe. Common areas are flame sensing, ignition, gas supply and venting. Photograph the flashing code and book service. Repeatedly cutting power to force more attempts just repeats a failed ignition sequence, which is exactly what the lockout is designed to prevent.
Can I clean the flame sensor myself?
We do not recommend it. The sensor sits inside the burner compartment of a live gas appliance, and its position relative to the flame matters. Cleaning it with the wrong material or reinstalling it slightly off causes the same failure again. Gas work in British Columbia requires TSBC certification. Have it cleaned or replaced during a service visit, where the flame signal can actually be measured afterward.
Why is my furnace short cycling only on the coldest days?
Cold days mean longer, harder runs, which is when a marginal airflow restriction finally pushes the heat exchanger past the high limit. On mild days the furnace never runs long enough to overheat. So a fault that appears only in a cold snap usually still means airflow: a filter, closed registers, a dirty blower wheel, or ductwork that cannot deliver what the furnace produces.
My furnace works but the AC does nothing. Is that a furnace problem?
It can be. In most homes here the indoor coil sits on the furnace and the furnace blower moves the cooled air. Set the thermostat fan to On. If the blower runs, look at the outdoor unit and the cooling call. If it does not, the fault is on the furnace side, and heating will likely fail next time you need it.
How do I know if I should repair or replace?
Consider the age of the unit, whether parts are still available for that model year, whether the heat exchanger has been stressed by repeated overheating, and how the repair compares to the value of the remaining service life. Ask for the manufacturer’s spec sheet or AHRI listing for any proposed replacement rather than general efficiency claims, and confirm current rebate terms directly with CleanBC or FortisBC.
Reviewed by the HeatLand Heating & Cooling team — licensed, insured, TSBC-certified HVAC contractor serving Metro Vancouver & the Fraser Valley since 1999. Error codes, specifications, pricing and rebate programs vary by model and change over time; confirm details against your unit’s own manual, a written quote, and the manufacturer or CleanBC/FortisBC. If you smell gas or your CO alarm sounds, leave the home and call the gas utility and a licensed technician from outside.