# 1578846 Rheostat | Genuine Volvo Penta Part

## 🔧 Product Description

This genuine Volvo Penta rheostat is a precision electrical sensing and indication component used in the instrument-panel illumination control. It is manufactured to the original Volvo Penta dimensions and interface requirements so the sender or switch retains the specified electrical range, mounting depth and signal relationship. Maintains the revised OEM service configuration. In service, it varies resistance in the panel-light circuit to adjust instrument illumination brightness. Fitment is controlled by the exact engine or product configuration and serialised parts list; confirm OEM number 1578846 against the installed assembly before ordering.

## 🚤 Compatibility

-   **Engine Family:** MD, TMD, AQD, THAMD, TAMD

Full model list at the end of this description.

## ⚙️ Key Features

-   Genuine Volvo Penta OEM part number 1578846
-   System group: Other Electrical Equipment
-   Net weight: 0.077 kg
-   Supersedes earlier part number 842918
-   Fits MD, TMD, TAMD, THAMD, AQD and MD100/MD120 series marine diesel engines

## 🔌 Function

The rheostat provides adjustable electrical resistance in a low-current circuit, typically allowing the brightness of instrument panel lighting to be varied. By altering resistance as the control is turned, it regulates the current reaching the connected circuit.

## ⚠️ Common Signs of Failure

-   Flickering or erratic panel illumination when the control is adjusted
-   No change in brightness across the full range of travel
-   Dead spots or intermittent contact as the control is rotated
-   Discolouration, overheating or a burnt smell at the resistance element
-   Corroded or loose terminals causing high resistance and voltage drop

## 🛠️ Service Notes

-   A rheostat is not polarity-sensitive and can be wired either way round, but check its current/wattage rating matches the connected instrument-lighting circuit before fitting a generic replacement - an undersized rheostat can overheat.

## 🔄 Supersession & Cross Reference

### OEM Supersession Chain

-   1578846 → Supersedes 842918 → Supersedes 842917

### OEM / Related Numbers

-   842918 earlier number superseded by this part
-   842919 earlier number superseded by this part
-   842917 earlier number superseded by this part

### Aftermarket / Verified Equivalents

-   SRP: R-78846

## 📦 Condition

-   Genuine Volvo Penta part
-   Brand new
-   Supplied in original or equivalent packaging

## 🔎 Full Model Compatibility

Typically suits:

-   Volvo Penta TAMD162C-C, TAMD162A, TAMD162C, TAMD162C-B
-   Volvo Penta AQD70BL, AQD70CL, AQD70C
-   Volvo Penta MD100A, MD100B, MD100B-CC
-   Volvo Penta TAMD122A, TAMD122A/C, TAMD122D
-   Volvo Penta TAMD120A, TAMD120B
-   Volvo Penta TAMD165A, TAMD165C
-   Volvo Penta TMD100A, TMD100C
-   Volvo Penta TMD120A, TMD120B
-   Volvo Penta MD120A
-   Volvo Penta MD70C
-   Volvo Penta TAMD102A
-   Volvo Penta TAMD103A
-   Volvo Penta TAMD121D
-   Volvo Penta TAMD163A-A
-   Volvo Penta TAMD70C
-   Volvo Penta TAMD74A
-   Volvo Penta THAMD70C
-   Volvo Penta TMD102A
-   Volvo Penta TMD121C
-   Volvo Penta TMD122A
-   Volvo Penta TMD70C

## Details

- **Price:** 177.25 AUD
- **Vendor:** Volvo Penta
- **Type:** Instruments & Gauges
- **Tags:** Volvo Penta Parts | Genuine Marine Engine & Service Components

## Variants

| Variant | Price | Available |
|---------|-------|-----------|
| Default Title | 177.25 AUD | In stock |

## Images

- 1578846 Rheostat | Genuine Volvo Penta Part

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> Source: [Sawley's Auto and Marine](https://www.sawleysautoandmarine.com.au/products/1578846-rheostat-genuine-volvo-penta)
> Updated: 2026-10-09