Getting Your Hands on Inter City Products Furnace Manuals
Most people searching for these manuals are standing in a basement looking at a dead unit. You probably already know you need the manual, but finding a clean, complete copy isn't as straightforward as it should be. Inter City Products was a mid-tier furnace manufacturer that operated mainly from the 1970s through the early 1990s before being absorbed or discontinued. That means the company is gone, the original filing system is gone, and anything that wasn't archived by HVAC distributors has degraded or been tossed. The official manuals for these units cover three main categories: installation, service, and parts. If you're a homeowner who just found a scratchy photocopy from 1987, that's about all most people end up with. If you're a technician, you need the full service version with wiring diagrams and troubleshooting charts. I spent a week tracking down a service manual for a 1983 Inter City Products IG-60 furnace last winter. Here's how it went. The company isn't listed in any current manufacturer directory. Their former regional distributor, mid-century heating supply, had a warehouse sale in 2004 where some manuals were sold by the pound. My first move was checking the National Weatherization Information Center archives and the EPA's ASHRAE historical document collection. Neither had anything on Inter City specifically. The next stop was eBay and specialty HVAC forums. You'll find scattered PDFs uploaded by individual technicians, but they're usually incomplete. I found the blower motor replacement section on one thread and the gas valve troubleshooting on another. I spent three hours cross-referencing the two scans to piece together the electrical schematic.
The only reliable source for complete original manuals is the HVAC Parts and Manual Archive at hvacmanualarchive.com. They maintain scanned copies from former distributor inventories. For Inter City Products specifically, they have installation guides for the IG and IGK series, the service manual with the wiring diagrams, and a parts breakdown for the heat exchanger assembly. The download is free but requires creating an account. Uploading your own copy helps them expand the collection, which is how they've recovered most of these documents over the years. Another option is contacting the old dealer network directly. Some independent HVAC shops that used to service Inter City units kept physical copies in their files. I called three shops in Ohio and one in Michigan that had serviced Inter City installations. One of them, a small operation in Youngstown, still had a shelf of original manuals from when they were the authorized dealer. They let me scan the service manual on-site for a five-dollar fee. That copy was complete and legible. The eBay scans are often blurry or missing pages because whoever uploaded them photocopied a deteriorated original. Here's the thing nobody tells you about these manuals: the wiring diagrams in the service manual are for the base configuration. If the furnace was upgraded with a variable-speed inducer motor or a secondary heat exchanger, the wiring changed and the manual doesn't always reflect that. I learned this the hard way on a unit in a 1978 build where the previous owner had installed an after-market draft inducer kit. The schematic showed a single-stage gas valve and a straight 24-volt low-voltage circuit. The actual wiring had a three-wire inducer connection that wasn't documented anywhere in the manual. I traced it back to the factory by finding a retrofit bulletin that Inter City had sent out in 1985, which had the modified diagram. These bulletins aren't included in any of the standard manuals. If you find a bulletin number reference in the manual's appendix, search for it using the furnace model number plus "service bulletin" on HVAC-t spare parts forums. There's a dedicated subforum on theremaintalk.com where technicians post these.
A more practical tip: the serial number plate on Inter City furnaces encodes the manufacturing date in the first four digits. It's not intuitive. The format is YYWW, meaning year and work week. A serial starting with 8312 was built in the twelfth week of 1983. Knowing this matters because Inter City changed their gas valve specifications mid-production. A 1983 model with a 1984 valve has a different manifold pressure setting than the same model with a 1983 valve. The manual lists a single pressure specification. I found this discrepancy on a unit where the combustion analysis kept reading high CO at the rated manifold pressure. Adjusting it per the manual specs made things worse. I checked the valve date code stamped on the solenoid body, confirmed it was a later replacement, and found the adjusted specification in a technical update. This took about ten minutes once I knew where to look. If you're working on an Inter City Products furnace and can't find a manual, there's a workaround using the parts list from a comparable Carrier or Bryant model from the same era. Inter City was a private-label brand that used many off-the-shelf components. The control board layout, gas valve connections, and thermostat wiring are often identical to contemporaneous Carrier units. The interlocking details differ in the heat exchanger section, so don't assume interchangeability there. But for electrical troubleshooting, a Carrier 58C manual from 1985 is functionally equivalent for about seventy percent of the low-voltage issues. The main limitation of relying on archived manuals is completeness. No single source has every model variation. The IG-60, IG-80, and IGK-60 manuals are well represented. The smaller models like the IS-40 and the commercial IK series are spotty. If you need those and can't find a scan, the best path is the parts diagram. Even if the service manual is missing, the parts breakdown usually shows component placement and numbering, which lets you identify and order replacements. Contacting an HVAC parts counter with the full model and serial number will get you the correct parts even without the manual.
Get the Full Details
For most people, the HVAC Parts and Manual Archive covers what you need. Create the account, download the service manual for your specific model series, and print the wiring diagram on cardstock so it survives a basement job site. Keep a pen light and a multimeter handy. The diagrams are small and low contrast on the scanned copies. Squinting at them in a dark mechanical room gets old fast.
