TP-851B Fenwal 35-66 Diagnostic Circuit Board

The TP-851B is a Fenwal 35-66 diagnostic circuit board with LED, the ignition/diagnostic control module for Re-Verber-Ray gas-fired tube heaters. It manages and monitors the heater's ignition sequence, using an onboard LED to signal fault/status conditions for troubleshooting. It is the control module called out in the parts breakdowns for the heaters it fits, seated in the control compartment and wired to the inducer, gas valve, and sensing components per the unit's wiring diagram.

Fits the CX3, DST, and DX3L family, with additional listings on HL3, CL3, LD3, LS3, DSRF, DSRL, and DSRS; see Fitment below for the full model list. It replaces the same board position referenced in each series' parts chart as "CIRCUIT BOARD ... TP-851B" or "35-66 Diagnostic Circuit Board." The manufacturer's parts store also lists this board under Fenwal Part # 35-665913-119 (Alt Part # 35-665913-119, also referenced as G90904), a same-brand OEM designation shown directly on the Re-Verber-Ray parts page rather than a separately sourced cross-reference.

It ships as the bare board; wire harness, mounting hardware, and inducer are not included unless listed separately on the model's own parts breakdown.

Confirm the exact board revision against the unit's parts breakdown before ordering: related boards (TP-851, TP-851C) look similar but are not interchangeable, since TP-851B is not interchangeable with the plain TP-851 (a different Micro-60-24 board used on RVA-2/HL-2/LD) or with TP-851C. As with all heater control-board work, shut off gas and disconnect power before servicing, verify wiring against the unit's installation sheet, and have a qualified technician confirm proper ignition operation after replacement. No standalone install sheet or datasheet was found for this part; consult the unit's own series installation manual for wiring detail.

Specifications

Cross-Reference & Fitment