An error code on the display of your tankless water heater, a shower that goes cold halfway through, a unit that just won’t fire — none of that is background noise. It’s your tankless heater telling you something’s wrong, and it rarely gets better on its own. That’s why we built our tankless water heater repair in San Jose around actually finding the problem, not guessing at it.
Fuse Service has been fixing tankless systems around San Jose for years, and our company is licensed and insured for exactly this kind of work. We’ve seen what the local water does to these units and what tends to fail first, so when we show up, we’re not starting from zero.
Most tankless failures fall into a handful of categories — ignition, flow, scale, venting. Below is what our techs run into most on calls across the city.
No Hot Water or Ignition Won’t Catch
The unit turns on, then shuts right back off — or never lights at all. Nine times out of ten it’s a worn igniter, a dead flame sensor, a gas supply hiccup, or a control board that’s stopped talking to the rest of the system.
Water Starts Hot, Then Goes Cold
Imagine you’re mid-shower. And all of a sudden the temperature drops out of nowhere. That’s usually a sizing issue. Sometimes the heat exchanger is clogged with scale or a sensor may be the root cause.
The Unit Won’t Kick On at Low Flow
Tankless water heaters operate with a very small water flow amount. If a fixture isn’t pulling enough water, nothing happens — often because the flow sensor is dirty or a valve isn’t fully open.
Scale Buildup Choking the Heat Exchanger
San Jose water is hard, and that’s exactly why mineral content coats the inside of the heat exchanger. Over time flow drops as well as efficiency drop, and eventually the unit overheats and shuts itself down.
Venting or Combustion Air Trouble
A blocked or disconnected vent will trip the safety shutoff almost instantly. We trace the entire vent run rather than just checking the outside termination, because the blockage is often further inside than people expect.
Condensate Drain and Neutralizer Issues
Condensing units produce acidic condensate that has to go somewhere. A clogged drain line or a spent neutralizer cartridge can throw error codes — and left alone, that acidic water can eat away at internal parts.
Recirculation Pump Acting Up
Got a recirc loop for instant hot water? When the pump seizes or the aquastat fails, you’re back to waiting at the tap like the loop was never installed.
Leaks, Valve Failures, and Strange Noises
A drip at a fitting, a pressure relief valve that won’t hold, popping or rattling sounds mid-cycle — all worth a look before they turn into something bigger.
Schedule a Free Estimate of Your Water Hetaer Project
Rinnai, Navien, Noritz, Rheem, Takagi, Bosch — we service them all, plus most other models installed around San Jose, residential or commercial. Every technician trains on manufacturer-specific diagnostics, so the fix is built around how your unit actually works, not a generic checklist. That’s the difference between tankless water heater service done right and a part swapped at random.
Repair, Maintenance, or Replacement?
Not every symptom means a new unit, and not every fix is worth chasing on an old one. A rough guide:
What’s Going On
What Usually Makes Sense
Occasional error code, unit otherwise fine
A diagnostic repair
Reduced flow, scale buildup, unit under 10 years old
Descaling and maintenance
Frequent shutdowns, climbing repair bills, unit 12+ years old
Time to think about replacement
No hot water, one part clearly at fault
A targeted repair
Repeated ignition or venting failures on an aging unit
A full system check
Not sure where yours lands? That’s what a diagnostic visit is for — we’ll give you a straight answer, not a sales pitch.
What Happens During a Service Visit
1.
First, we walk the system. The technician pulls the error history, checks the vent, and tests gas pressure and water flow before touching anything.
2.
Then we narrow it down. Once the symptoms point to a specific part — igniter, sensor, heat exchanger, pump — we confirm it with actual testing instead of swapping parts to see what sticks.
3.
Next comes the fix. Depending on what we find, that might mean a new part, a full heat exchanger flush, clearing the vent, or servicing the recirc pump. You'll know what's being done before we start.
4.
Last, we test it. The unit runs through several cycles while we check flow, temperature, and confirm the error code is actually gone — not just reset.
Residential and Commercial Tankless Repair
Fuse Service works on single-unit home systems and larger commercial setups alike. Multiple-unit dwellings, restaurants, and offices often use more powerful units or systems operating in parallel. That means they require their own maintenance schedule.
Our commercial tankless water heater repair covers everything from replacing a single faulty part to a complete diagnostic inspection of the system. This gives building owners and managers access to a team of specialists who are well-versed in both the equipment and the potential consequences of a hot water outage for residents or customers.
Why San Jose Property Owners Call Fuse Service
Licensed, Insured, and Not New at This
We’re a fully licensed and insured contractor with years of tankless repair work behind us across San Jose and the Bay Area. That experience shows up as fewer callbacks and repairs that actually hold.
Straight Answers, No Upselling
Every tankless water heater technician on our team will tell you what’s wrong, what it costs, and whether repair or replacement is the smarter move — not whichever answer sells more.
We Show Up Fast
A cold shower doesn’t wait for a convenient time slot. Tankless calls get priority whenever possible, and we work to get a technician out quickly, especially when there’s no hot water at all.
Posted on Yelp
Arun S.
Great work. Thanks Igor and thanks Chris for a professional work done. Our Air conditioning system needed work and you were spot on diagnostics and fix .
Posted on Yelp
Eric A.
Quick easy and painless. Not the cheapest, but they do quality work. I had my bathroom drain cleaned out and pipes snaked.
Posted on Yelp
Stephanie W.
We're just about to have our heat pump and new water heater installed, so I can't speak to that experience yet, but I had to say how helpful their sales rep, Jeff, was with all of my questions to get settled into a plan. I'm one of those people who like to know what's going on line by line, and his patience and knowledge was very appreciated!
Posted on Yelp
Nicasio C.
Received professional service from Fuse from the start of the project to the finish. Project completed was AC and furnace replacement to heat pump and air handler.
Posted on Yelp
Nate M.
Great price to value/service ratio. No complaints and would use their service again.
Posted on Yelp
Frank C.
I had a need to replace our 50G gas water heater. Received several quotes from various contractors. Fuse was the most cost-effective proposal. Quote included new Bradford White heater, new expansion tank (did not have one before), new gas supply line to the heater, new drain pan, new Corro-Protec powered anode to prevent corrosion, and city permit. Installation was smooth. Workmanship excellent. Passed inspection with no issues.
Posted on Yelp
Han Wook C.
Henry and Alex did a fantastic job installing our new heat pump system! They worked hard over two days to get everything set up perfectly. They were punctual, professional, respectful of our home, and extremely knowledgeable. The new system is running great. Huge thanks to Henry and Alex for their hard work--I definitely recommend this team for your HVAC needs!
Posted on Yelp
Matt B.
Update: In what I am pretty convinced was a total coincidence, shortly after the heat pump was installed our gas hot water heater stopped working. I couldn't find anything that the installer would have done to cause it since the symptom was that the gas flame would not stay on. I called Fuse to see what they had to say and within a hour two technicians came out to take a look. After a couple hours of troubleshooting they thought it might be the control board. Of note they didn't charge us for their time. The gas HWH was to be replaced by Fuse with a heat pump based HWH so it seemed silly to invest much effort. Unfortunately there wasn't one of their electricians available for a couple of weeks to install the needed sub-panel. On a follow up call to Fuse, I reminded them that we also have an EV charger in the garage that they might be able to temporarily "borrow" the circuit. The next day the team of Ronnie and Alex came out and installed the new HWH using the EV charger's circuit (having to use a public charger was a small price to pay to having hot water). Once again, a professional job with great attention to detail. Last week Zorik the electrician arrived as scheduled to complete the installation. He worked with me on where I would prefer the sub-panel be installed. Within a few hours, our EV charger was back in business. I appreciated that Zorik took the time to review what breakers were moved so that I could update my records. I was confident that the job (and the others) were all were properly compliant with the building codes. Worth noting, the technician from an independent company came out to do the duct work testing (which passed). As he was leaving the subject of Fuse came up. His comment was that they are the best in the Bay Area.
Posted on Yelp
Jahrell H.
Sergei did an excellent job installing our RO system under the sink and he fixed a leak from plumbing under our home. He is an excellent plumber.
Schedule Tankless Water Heater Repair in San Jose
If your unit’s throwing codes, running cold, or just isn’t itself anymore, don’t wait it out. Book your tankless water heater repair in San Jose online, request a callback, or call us directly — we’ll get a technician on the schedule and your hot water sorted.
Very often it comes down to ignition failure, a clogged flow sensor, or an interrupted gas supply. If flipping the unit off and back on doesn’t fix it, that’s usually the point where tankless water heater repair in San Jose from someone who knows these systems beats another round of guessing.
If possible, write down the error code, turn off the unit if it is leaking water or making unusual noises, and call a specialist in instant-heat water heaters. The code itself usually directly indicates the cause of the malfunction, so once a specialist inspects the unit, a thorough diagnostic test is rarely necessary.
It comes down to the part and how far the problem’s gone. Swapping a sensor or igniter costs a lot less than replacing a heat exchanger or control board. Most tankless water heater service calls come with a real number upfront, before any work starts — not a surprise on the final invoice.
With how hard the water runs here, once a year is a good rule of thumb. Homes with a softener can usually stretch that to every 18 to 24 months.
Most jobs wrap up in one visit, usually an hour or two. Bigger issues, like a failed heat exchanger, might need a second visit if a part has to be ordered.
Past 12 years old, dealing with repeat failures, or the repair bill is getting close to the price of a new unit — that’s usually when replacement wins out.
Yes. We handle commercial tankless water heater repair for apartment buildings, restaurants, and offices, including paralleled and larger-capacity setups.
Don't Take Our Word for It — Check Out Our Reviews!
Posted on Yelp
Arun S.
Great work. Thanks Igor and thanks Chris for a professional work done. Our Air conditioning system needed work and you were spot on diagnostics and fix .
Posted on Yelp
Eric A.
Quick easy and painless. Not the cheapest, but they do quality work. I had my bathroom drain cleaned out and pipes snaked.
Posted on Yelp
Stephanie W.
We're just about to have our heat pump and new water heater installed, so I can't speak to that experience yet, but I had to say how helpful their sales rep, Jeff, was with all of my questions to get settled into a plan. I'm one of those people who like to know what's going on line by line, and his patience and knowledge was very appreciated!
Posted on Yelp
Nicasio C.
Received professional service from Fuse from the start of the project to the finish. Project completed was AC and furnace replacement to heat pump and air handler.
Posted on Yelp
Nate M.
Great price to value/service ratio. No complaints and would use their service again.
Posted on Yelp
Frank C.
I had a need to replace our 50G gas water heater. Received several quotes from various contractors. Fuse was the most cost-effective proposal. Quote included new Bradford White heater, new expansion tank (did not have one before), new gas supply line to the heater, new drain pan, new Corro-Protec powered anode to prevent corrosion, and city permit. Installation was smooth. Workmanship excellent. Passed inspection with no issues.
Posted on Yelp
Han Wook C.
Henry and Alex did a fantastic job installing our new heat pump system! They worked hard over two days to get everything set up perfectly. They were punctual, professional, respectful of our home, and extremely knowledgeable. The new system is running great. Huge thanks to Henry and Alex for their hard work--I definitely recommend this team for your HVAC needs!
Posted on Yelp
Matt B.
Update: In what I am pretty convinced was a total coincidence, shortly after the heat pump was installed our gas hot water heater stopped working. I couldn't find anything that the installer would have done to cause it since the symptom was that the gas flame would not stay on. I called Fuse to see what they had to say and within a hour two technicians came out to take a look. After a couple hours of troubleshooting they thought it might be the control board. Of note they didn't charge us for their time. The gas HWH was to be replaced by Fuse with a heat pump based HWH so it seemed silly to invest much effort. Unfortunately there wasn't one of their electricians available for a couple of weeks to install the needed sub-panel. On a follow up call to Fuse, I reminded them that we also have an EV charger in the garage that they might be able to temporarily "borrow" the circuit. The next day the team of Ronnie and Alex came out and installed the new HWH using the EV charger's circuit (having to use a public charger was a small price to pay to having hot water). Once again, a professional job with great attention to detail. Last week Zorik the electrician arrived as scheduled to complete the installation. He worked with me on where I would prefer the sub-panel be installed. Within a few hours, our EV charger was back in business. I appreciated that Zorik took the time to review what breakers were moved so that I could update my records. I was confident that the job (and the others) were all were properly compliant with the building codes. Worth noting, the technician from an independent company came out to do the duct work testing (which passed). As he was leaving the subject of Fuse came up. His comment was that they are the best in the Bay Area.
Posted on Yelp
Jahrell H.
Sergei did an excellent job installing our RO system under the sink and he fixed a leak from plumbing under our home. He is an excellent plumber.
Get in touch
Feel Free to Contact Us or Book Services
Fuse Service – your best solution for accurate, immediate, and professional help with all of your major service needs.
