July 19, 2026 Jerry Pavlic

Tennant CS16 Service Field Guide: Advanced Diagnostics & Component Testing

1. QUICK SPECIFICATIONS & BENCHMARKS MATRIX

Electrical System Benchmarks

Operating System Voltage (Battery Model): $24\text{V DC} \pm 1\text{V}$
Solenoid Valve Terminal Voltage: 21.4V - 25V DC (when handle lever is pulled)
Power Board MOS-FET Thermal Cutoff Limit: $150^\circ\text{C}$
Board Mounting Screw Torque: $3\text{ Nm}\ (26.55\text{ lbf-in})$ (Must apply thermal conductive paste to back plate)
Brush Motor Mounting Bolt Torque: $9\text{ Nm}\ (79.66\text{ lbf-in})$
Brush Head Pivot Bolt Torque: $23\text{ Nm}$

Motor Current Draw & Wear Limits Table

Component	Test Condition	Min Current	Max Current	Wear Threshold / Replacement Limit
24V DC Brush Motor	No Load (Brush Raised)	$2.0\text{ A}$	$3.5\text{ A}$	Carbon brush length $< 8.0\text{ mm}\ (0.31\text{ in})$
24V DC Brush Motor	Light Load (Empty Tank)	$7.0\text{ A}$	$9.0\text{ A}$	Replace all 4 carbon brushes simultaneously
24V DC Brush Motor	Full Load (Full Tank, Standard Brush)	$9.0\text{ A}$	$11.0\text{ A}$	Cutoff threshold: > 15 A for 20 sec
24V DC Suction Motor	No Load (Tank Removed)	$13.0\text{ A}$	$17.0\text{ A}$	Carbon brush length $< 6.0 - 8.0\text{ mm}$
24V DC Suction Motor	Overload Limit	—	$> 30\text{ A}$	Cutoff threshold: > 30 A for 20 sec

2. DISPLAY DASHBOARD ALARM CODES & METER FLOWCHART

NOTE: Internal motor thermal trip, blown individual motor fuses, or severed motor power cables do not display dashboard error codes.

                     DASHBOARD LED ERROR IDENTIFICATION
                                     │
    ┌───────────────────┬────────────┴───────┬───────────────────┐
    ▼                   ▼                    ▼                   ▼
2 FLASHES           2 FLASHES            4 FLASHES          FAST FLASHING
(Brush LED)         (Suction LED)        (Brush LED)        (Both LEDs)
    │                   │                    │                   │
Short Circuit /     Short Circuit /      Brush Motor         Power Board MOS-FET
Peak Current        Peak Current         Internal Thermal    Overheating
    │                   │                Protector Tripped   (>150°C)
    │                   │                    │                   │
    ├─► Check motor     ├─► Check motor      ├─► Check for       ├─► Allow 15 min
    │   wiring short.       wiring short.        motor binding.      cool-down.
    │                   │                    │                   │
    └─► Verify rotor    └─► Check fan        └─► Test continuity └─► Check current
         spins free.         rotates free.       on 4-pin purple-    draw on both
                                                 black wires.        motors.

Detailed Error Troubleshooting Steps

2 Quick Flashes — Brush Motor Short Circuit Protection

Disconnect battery power.
Rotate brush manually to ensure motor is not mechanically locked/jammed.
Disconnect power harness from brush motor terminals. Check for continuity/short to frame.
Test motor directly with isolated 24V source. If motor draws excessive peak current, inspect rotor/commutator or replace motor assembly.

2 Slow Flashes — Motor Overload

Brush Motor Limit: Exceeding 15 A for > 20 seconds
Suction Motor Limit: Exceeding 30 A for > 20 seconds
Fix Action: Check brush pad aggressiveness/friction on floor surface , inspect carbon brushes , and check for string/debris bound in the drive reduction gearbox.

4 Flashes — Brush Motor Thermal Protector Tripped

Motor thermal cutout is a Normally Closed (NC) switch operating between $80^\circ\text{C} - 110^\circ\text{C}$ .
Bench Check: Detach the 4-pin connector on the main harness and check continuity across the two purple-black wires.
If open-circuit while motor is cool, replace the internal thermal protector.

3. COMPONENT DIAGNOSTIC DECISION TREES

Tree A: Machine Completely Inoperative (No Display LEDs)

Check Battery Voltage: Ensure voltage across main terminals is > 21.5V DC
Check Fuse F1: Inspect 30A Main Fuse on battery model (8A Fuse F1 on corded model).
Verify Charger Lockout Relay: Disconnect battery charger bullet connectors E1 and bridge harness connectors E2 to bypass charger interlock relay. If control panel powers on, replace charger module.
Check Ribbon Cable: Test 10-pole flat ribbon cable for continuity pin-to-pin between function board and power board.

Tree B: Solution / Water Flow Failure

                          NO WATER AT BRUSH HEAD
                                     │
      ┌──────────────────────────────┴──────────────────────────────┐
      ▼                                                             ▼
[ SOLENOID CLICK AUDIBLE ]                             [ NO SOLENOID CLICK ]
      │                                                             │
      ├─► Clean inline solution filter (if equipped).               ├─► Verify 21.4V-25V DC across valve
      │                                                                 fast-on terminals when lever pulled.
      ├─► Flush solution dispensing cock under tank.                │
      │                                                             ├─► IF VOLTAGE PRESENT: Solenoid coil
      └─► Disassemble solenoid valve & clear diaphragm                  faulty or valve membrane seized.
          outlet hole E.                                                Replace solenoid coil/assembly.
                                                                    │
                                                                    └─► IF NO VOLTAGE: Test output from
                                                                        power board contact J3 / check 10-pole
                                                                        ribbon cable continuity.

4. POWER BOARD & CHARGER SERVICE PROTOCOL

Replacing the Power Control Card

Thermal Dissipation Safety: Clean mounting plate thoroughly. You must apply a fresh layer of thermally conductive silicone paste to the back of the new power card prior to mounting.
Torque Spec: Tighten all 4 board mounting bolts E to 3 NM. Do not over-torque.

Battery Charger DIP Switch Configuration (SW2)

When swapping battery chemistry, configure switch SW2 on the internal charger board:

      EXIDE GEL (Default)           DISCOVER AGM                 LEAD-ACID (WET)
        [ SW2 Board ]               [ SW2 Board ]                [ SW2 Board ]
        ┌───────────┐               ┌───────────┐                ┌───────────┐
     1  │  ■  OFF   │            1  │  ■   ON   │             1  │  ■  OFF   │
     2  │  ■  OFF   │            2  │  ■   ON   │             2  │  ■  OFF   │
        └───────────┘               └───────────┘                └───────────┘

Confirmation Verification: Upon plugging AC power into wall, observe status LED:
- 2 Green Flashes: Configured for Gel / AGM profile.
- 2 Red Flashes: Configured for Wet / Lead-Acid profile.

Looking for Replacement Parts or Technical Support?

Whether you need replacement squeegee blades, brush motors, filters, or battery care supplies, keeping OEM-spec parts on hand ensures minimal downtime. Contact our service team or explore our catalog for exact-fit replacement parts for Tennant, Nobles, and other leading floor scrubber brands. Shop Tennant CS16 Parts

Previous article Replacing Just One Scrubber Battery? Why You’re Cooking Your New Investment (Literally)

Next article Tennant CS16 Shift Supervisor Guide: Preventative Care & First-Line Troubleshooting