Cummins Block Heaters: ISX, ISB, 8.3, N14 & 855 Big Cam
Cummins engines outlive the trucks around them, which is why the heater question is always asked engine-first: not "what fits a 2005 Freightliner" but "what fits an ISX." The tables below cover the highway engines (ISX, ISM, N14, 855), the mid-range workhorses (ISB/QSB 5.9 and 6.7, C-series 8.3, ISL), and the industrial K-series, with the coolant heater part numbers, wattage, and install port for each family.
Most Cummins heaters are threaded immersion elements that replace a pipe plug in or near the oil cooler — a wrench job, not a freeze-plug fight. The classic 855 and N14 use a bolt-on plate heater that replaces the water jacket access plate instead. Both styles put the element directly in the coolant, which is what you want at -30°C.
Heater part numbers by application
Part numbers from the Zerostart / Phillips & Temro heavy-duty application guide, with Kat's equivalents where both catalogs list the engine. Numbers are occasionally superseded — confirm against a current catalog or dealer before ordering.
ISX & QSX (July 2007 and newer)
| Part no. | Watts | Volts | Size | Type | Repl. cord |
|---|---|---|---|---|---|
| 3500107 | 1,500 W | 120 V | 26 mm | Immersion | 3600008 |
Installs on the right side of the engine, in the 26 mm port.
Signature 600, ISX, QSX (15L / 915 CID, pre-July 2007)
| Part no. | Watts | Volts | Size | Type | Repl. cord |
|---|---|---|---|---|---|
| 3500038 | 1,500 W | 120 V | Plate | Immersion | 3600008 |
| 3500108 | 1,500 W | 240 V | Plate | Immersion | 8608377 |
Bolt-on plate heater replacing the water jacket access plate.
ISB 6.7L & QSB (2007+), ISB/QSB 3.9L & 5.9L
Same heater the Ram 2500/3500 pickups use — this is the "6.7 Cummins block heater."
| Part no. | Watts | Volts | Size | Type | Repl. cord |
|---|---|---|---|---|---|
| 3500022 | 750 W | 120 V | 3/4" NPT | Immersion | 3600008 |
| 3500110 | 750 W | 240 V | 3/4" NPT | Immersion | 8608377 |
Threads into the 3/4" NPT port to the rear of the oil cooler.
B Series 1987–2002: 4B/4BT 3.9L, 6B/6BT 5.9L
| Part no. | Watts | Volts | Size | Type | Repl. cord |
|---|---|---|---|---|---|
| 3500030 | 750 W | 120 V | 58 mm | Freeze plug | 3600008 |
| 8601666 | 750 W | 240 V | 58 mm | Freeze plug | 8608377 |
Replaces the freeze plug on the right side of the engine. O-ring and clamp service kit: 3500002.
C Series 8.3L: 6C8.3, 6CT8.3, 6CTA8.3
| Part no. | Watts | Volts | Size | Type | Repl. cord |
|---|---|---|---|---|---|
| 8601860 | 1,000 W | 120 V | 58 mm | Freeze plug | 3600008 |
| 8601852 | 1,000 W | 240 V | 58 mm | Freeze plug | 8608377 |
Replaces the freeze plug on the right rear side of the engine. O-ring and clamp service kit: 3500002.
ISC & QSC 8.3L, ISL 8.9L
| Part no. | Watts | Volts | Size | Type | Repl. cord |
|---|---|---|---|---|---|
| 3500032 | 1,000 W | 120 V | 3/4" NPT | Immersion | 3600008 |
Threads into the upper 3/4" NPT port at the front of the oil cooler.
L10, M11, ISM, QSM11
| Part no. | Watts | Volts | Size | Type | Repl. cord |
|---|---|---|---|---|---|
| 8600015 | 1,500 W | 120 V | 38 mm thd | Immersion | 3600008 |
| 8600031 | 1,500 W | 240 V | 38 mm thd | Immersion | 8608377 |
Installs in the heater casting on the right rear side of the engine.
M11 (2000 and newer)
| Part no. | Watts | Volts | Size | Type | Repl. cord |
|---|---|---|---|---|---|
| 3500042 | 1,500 W | 120 V | Plate | Immersion | 3600008 |
| 3500109 | 1,500 W | 240 V | Plate | Immersion | 8608377 |
Installs on the right rear side of the engine.
N Series 855 CID / 14L: NT315, N14-330/460, Big Cam IV, 88NT, 444
| Part no. | Watts | Volts | Size | Type | Repl. cord |
|---|---|---|---|---|---|
| 8601003 | 1,000 W | 120 V | Plate | Immersion | 3600008 |
| 8601046 | 1,500 W | 120 V | Plate | Immersion | 3600008 |
| 8601062 | 1,500 W | 240 V | Plate | Immersion | 8608377 |
Plate immersion heater replacing the water jacket access plate on the side of the engine. Alternate for engines with a rear-plate hose connection: 8601526 (1,500 W/120 V).
Kat's equivalents: 30111 (120 V) / 31111 (240 V) for N/NH engines; 30101 / 31101 for Big Cam and N14.
855 CID alternates (cab-over installs, O-ring blocks)
| Part no. | Watts | Volts | Size | Type | Repl. cord |
|---|---|---|---|---|---|
| 3500036 | 1,500 W | 120 V | 1-1/2" NPT | Immersion | 3600008 |
| 3500023 | 1,500 W | 120 V | 1-5/8" STOR | Immersion | 3600008 |
3500036 threads into the rear face above the flywheel (easier on cab-overs). 3500023 fits 1996+ O-ring style blocks.
K Series: KT19, KT450, KT1150, KTA525; QSK
| Part no. | Watts | Volts | Size | Type | Repl. cord |
|---|---|---|---|---|---|
| 3500017 | 1,500 W | 120 V | 1-3/4"-18 thd | Immersion | 3600008 |
Replaces the large hex plug at the upper front or centre thread position on the oil cooler cover. Point element to 6 or 12 o'clock.
Compare heater and cord buying options
Check the application table for your exact engine. Cords, heater elements and surface pads are separate products.
Part reference
Zerostart 3500107
Catalog starting point: confirm exact engine code, year and installation with the manufacturer.
No exact purchase listing verified yet. These links search Amazon; confirm the part before buying.
Affiliate links. As an Amazon Associate, we earn from qualifying purchases.
Part reference
Zerostart 3600008
Industrial replacement cord, 15 A, 16/3 HPN, silicone connector K in PTI catalog. Cord only; not a heating element.
Cord / harness only — no heating element.
No exact purchase listing verified yet. These links search Amazon; confirm the part before buying.
Affiliate links. As an Amazon Associate, we earn from qualifying purchases.
Part reference
Zerostart 3500038
Catalog starting point: confirm exact engine code, year and installation with the manufacturer.
No exact purchase listing verified yet. These links search Amazon; confirm the part before buying.
Affiliate links. As an Amazon Associate, we earn from qualifying purchases.
Part reference
Zerostart 3500108
Catalog starting point: confirm exact engine code, year and installation with the manufacturer.
No exact purchase listing verified yet. These links search Amazon; confirm the part before buying.
Affiliate links. As an Amazon Associate, we earn from qualifying purchases.
Part reference
Zerostart 8608377
Legacy fitment associations are not independently verified vehicle-specific purchase recommendations.
Cord / harness only — no heating element.
No exact purchase listing verified yet. These links search Amazon; confirm the part before buying.
Affiliate links. As an Amazon Associate, we earn from qualifying purchases.
Amazon buying options
Zerostart 3500022
Catalog starting point: confirm exact engine code, year and installation with the manufacturer.
Choose your Amazon store
Affiliate links. As an Amazon Associate, we earn from qualifying purchases.
Part reference
Zerostart 3500110
Catalog starting point: confirm exact engine code, year and installation with the manufacturer.
No exact purchase listing verified yet. These links search Amazon; confirm the part before buying.
Affiliate links. As an Amazon Associate, we earn from qualifying purchases.
Part reference
Zerostart 3500030
Catalog starting point: confirm exact engine code, year and installation with the manufacturer.
No exact purchase listing verified yet. These links search Amazon; confirm the part before buying.
Affiliate links. As an Amazon Associate, we earn from qualifying purchases.
Part reference
Zerostart 8601666
Catalog starting point: confirm exact engine code, year and installation with the manufacturer.
No exact purchase listing verified yet. These links search Amazon; confirm the part before buying.
Affiliate links. As an Amazon Associate, we earn from qualifying purchases.
Part reference
Zerostart 8601860
Catalog starting point: confirm exact engine code, year and installation with the manufacturer.
No exact purchase listing verified yet. These links search Amazon; confirm the part before buying.
Affiliate links. As an Amazon Associate, we earn from qualifying purchases.
Part reference
Zerostart 8601852
Catalog starting point: confirm exact engine code, year and installation with the manufacturer.
No exact purchase listing verified yet. These links search Amazon; confirm the part before buying.
Affiliate links. As an Amazon Associate, we earn from qualifying purchases.
Part reference
Zerostart 3500032
Catalog starting point: confirm exact engine code, year and installation with the manufacturer.
No exact purchase listing verified yet. These links search Amazon; confirm the part before buying.
Affiliate links. As an Amazon Associate, we earn from qualifying purchases.
Part reference
Zerostart 8600015
Catalog starting point: confirm exact engine code, year and installation with the manufacturer.
No exact purchase listing verified yet. These links search Amazon; confirm the part before buying.
Affiliate links. As an Amazon Associate, we earn from qualifying purchases.
Part reference
Zerostart 8600031
Catalog starting point: confirm exact engine code, year and installation with the manufacturer.
No exact purchase listing verified yet. These links search Amazon; confirm the part before buying.
Affiliate links. As an Amazon Associate, we earn from qualifying purchases.
Part reference
Zerostart 3500042
Catalog starting point: confirm exact engine code, year and installation with the manufacturer.
No exact purchase listing verified yet. These links search Amazon; confirm the part before buying.
Affiliate links. As an Amazon Associate, we earn from qualifying purchases.
Part reference
Zerostart 3500109
Catalog starting point: confirm exact engine code, year and installation with the manufacturer.
No exact purchase listing verified yet. These links search Amazon; confirm the part before buying.
Affiliate links. As an Amazon Associate, we earn from qualifying purchases.
Part reference
Zerostart 8601003
Catalog starting point: confirm exact engine code, year and installation with the manufacturer.
No exact purchase listing verified yet. These links search Amazon; confirm the part before buying.
Affiliate links. As an Amazon Associate, we earn from qualifying purchases.
Part reference
Zerostart 8601046
Catalog starting point: confirm exact engine code, year and installation with the manufacturer.
No exact purchase listing verified yet. These links search Amazon; confirm the part before buying.
Affiliate links. As an Amazon Associate, we earn from qualifying purchases.
Part reference
Zerostart 8601062
Catalog starting point: confirm exact engine code, year and installation with the manufacturer.
No exact purchase listing verified yet. These links search Amazon; confirm the part before buying.
Affiliate links. As an Amazon Associate, we earn from qualifying purchases.
Part reference
Zerostart 3500036
Catalog starting point: confirm exact engine code, year and installation with the manufacturer.
No exact purchase listing verified yet. These links search Amazon; confirm the part before buying.
Affiliate links. As an Amazon Associate, we earn from qualifying purchases.
Part reference
Zerostart 3500023
Catalog starting point: confirm exact engine code, year and installation with the manufacturer.
No exact purchase listing verified yet. These links search Amazon; confirm the part before buying.
Affiliate links. As an Amazon Associate, we earn from qualifying purchases.
Part reference
Zerostart 3500017
Catalog starting point: confirm exact engine code, year and installation with the manufacturer.
No exact purchase listing verified yet. These links search Amazon; confirm the part before buying.
Affiliate links. As an Amazon Associate, we earn from qualifying purchases.
Installing a Cummins coolant heater yourself
The NPT-thread heaters (ISB, ISC/ISL, 855 alternates) are the easiest DIY install in the diesel world: drain a few litres of coolant below the port, remove the pipe plug, apply thread sealant rated for coolant, torque the heater in, refill and burp the system. Budget an hour the first time. The freeze-plug style (B-series, C 8.3) is more involved — the old plug has to be punched and levered out, the bore cleaned, and the heater seated square with its O-ring — but it's still a driveway job with hand tools.
Plate heaters on the 855/N14 replace the water jacket access plate: unbolt the old plate, clean the gasket surface, install the heater plate with a new gasket, and torque evenly. Never run any immersion heater dry — plug it in only when the cooling system is full, or the element burns out in minutes.
One warning that applies to every engine on this page: match the voltage to your outlet. The 240 V versions are for yard shore-power pedestals and hard-wired shop circuits. Plugging a 120 V heater into 240 V destroys it instantly; a 240 V heater on 120 V just quietly makes a quarter of its rated heat.
Grid heaters are not block heaters
Every ISB and most modern Cummins engines have a factory intake grid heater — the reason for the "wait to start" light. It heats the intake air during cranking; it does nothing for the block, the oil, or the coolant while the truck sits overnight. A block heater and the grid heater solve different halves of the cold-start problem, and in a Prairie winter a working ISX or ISB wants both.
FAQ
Where is the block heater on a Cummins ISX?
On July 2007 and newer ISX/QSX engines the heater port is on the right side of the engine — the Zerostart heater is 3500107 (1,500 W, 26 mm immersion). Earlier 15-litre ISX/Signature 600 engines use a bolt-on plate heater (3500038 in 120 V) that replaces the water jacket access plate.
What block heater fits a 5.9 or 6.7 Cummins?
1989–2002 5.9L (12-valve and early 24-valve B-series) take the 58 mm freeze-plug heater 3500030 (750 W). 2003+ 5.9L and all 6.7L ISB engines take the 3/4" NPT immersion heater 3500022 (750 W), which threads in behind the oil cooler — the same heater Ram installs at the factory.
How many watts should a semi-truck block heater be?
Heavy-duty highway diesels run 1,000–1,500 W coolant heaters — the tables above list the exact rating per engine family. That's enough to hold a 15-litre block 20–30°C above ambient overnight. Fleets in the coldest regions often add an oil-pan pad and a battery blanket on the same circuit.
Compare buying options
Amazon buying options
Kat's 13150 circulating tank heater, 1,500 W
Plumbs into a heater hose and thermosiphons hot coolant through the whole engine — the serious option for big diesels, tractors, and equipment with no frost-plug access.
Confirm the exact specification and application in the listing before ordering.
Choose your Amazon store
Affiliate links. As an Amazon Associate, we earn from qualifying purchases.
Amazon buying options
NOCO Boost GB150 lithium jump starter, 3000 A
The pro-grade boost pack — rated for gas engines to 9 L and diesels to 7 L. What actually turns over a cold Cummins or DT466 when the batteries give up.
Confirm the exact specification and application in the listing before ordering.
Choose your Amazon store
Affiliate links. As an Amazon Associate, we earn from qualifying purchases.
Amazon buying options
Howes Diesel Treat anti-gel, 64 oz
The trucker-standard winter conditioner — prevents gelling, adds lubricity, no alcohol. The 64 oz jug treats hundreds of litres; dose every fill from November on.
Confirm the exact specification and application in the listing before ordering.
Choose your Amazon store
Affiliate links. As an Amazon Associate, we earn from qualifying purchases.
Diesel pickups we catalogue fitment for
Part numbers, wattage and cord routing for the light-duty diesels that share a yard with this equipment.
Should you plug in tonight?
Enter your city — we check tonight's forecast and give you a straight answer based on the temperature thresholds that matter.
Keep reading