Main Power Relay Troubleshooting
1. Verify PCB box has a good GROUND connection. Check resistance between the
body of the box to a good ground.
2. Verify correct battery polarity. Verify transmission in Neutral, brake set.
3. Verify 24 VDC at Term C (81)
a. No: check battery connections and wiring to PCB to get power to C (81)
b. Yes: proceed
4. Turn on BATTERY SWITCH – gages should activate
a. Yes: proceed to STARTER relay section below
b. No: Proceed…
5. Verify 24 VDC at Term A (459)
a. NO: Check Battery switch and wiring to get power to A (459)
b. YES: Check Term D – should be 24 VDC
i. YES: check wiring from Term D to loads (gages, alarms, etc)
ii. NO: PCB is bad; replace it or remove cover to
troubleshoot further.
6. With PCB cover removed and PCB plugged in, ground the chassis (backing plate)
that the relays are mounted on.
7. Verify power at Term C (81). Turn “ON” Battery Switch. Verify power at Term
A (459).
8. Check for power at Power Relay coil terminal (blue wire?):
a. NO: PCB circuitboard is bad – replace PCB. (verify by using jumper to
apply 24 VDC to coil terminal – relay should pull in, although it could be
bad too).
b. YES: if still no power at Term D (5) the relay is bad. Replace relay or
entire PCB.
Starter Relay Troubleshooting
1. Turn Battery Switch ON, verify gages are on.
2. Turn Ignition Switch to START.
a. Starter works : Done
b. No starter: proceed
3. Check Term E (499) for power while activating IGN/START switch::
a. NO: Check for power at wire 498 at the Neutral Safety Switch (NSS):
i. YES: check for power at wire 499 at NSS
1. NO: Check/Replace NSS (jumper it to confirm)
2. YES: check wire 499 from NSS to PCB
ii. NO: check Ignition Switch and wiring
b. YES: Check for power at Term B (74):
i. YES: check for continuity to starter solenoid; the starter solenoid
or starter may be bad
ii. NO: PCB is bad – replace PCB or proceed:
4. With PCB cover removed and PCB plugged in, ground the chassis (backing plate)
that the relays are mounted on.
5. Verify power at Terms A (459), C (81), and D (5).
6. Turn Ignition Switch to START. Verify power at Term E (499) Check for power
at coil terminal of starter relay (blue wire).
a. Yes: Check for power at Term B (74)
i. YES: Check wiring to starter, starter solenoid or starter may be
bad.
ii. NO: Starter relay in PCB is bad. Replace relay or entire
PCB.
b. No: PCB circuitboard is bad. Replace PCB. (Verify by applying 24 VDC
to relay output terminal/Term B (74) – starter should crank).
