EM40 Fiat Interface Unit
Overview
The EM40 is an interface between the Fiat base vehicle and the habitation electrics, and is used in conjunction with an EC500 or EC700 power supply system.
The unit provides fused outputs for a the 12V fridge, vehicle battery supply and tow bar. It also has a marker lights output and passes all signals from the Fiat base signal so they can be used by other systems ( door lock/unlock, ignition on, engine running).
It was used in all Auto-Trail Fiat motorhomes up to 2021. In 2022 the EM40 is fitted in models with a small fridge/freezer; In models fitted with a large fridge/freezer the EM41 interface fuse box is fitted.
It is used in all Auto-Sleepers Fiat based motorhomes. In Mercedes based motorhomes the EM45 is used, see here for more details: EM45 Mercedes Interface Unit
Fuse Allocation
FUSE RATING USAGE
Fuse 1 20A Vehicle Battery See Note1 below.
Fuse 2 20A Towing Permanent
Fuse 3 5A Markers
Fuse 4 Spare
Fuse 5 20A Fridge D+
Fuse 6 20A Towing D+
Fuse 7 20A Fridge Permanent
Fuse 8 Spare
Note 1. In Auto-Sleepers vehicles factory witted with a lithium battery Fuse 1 is rated at 25A
Use only good quality fuses and DO NOT replace any fuse with one of a higher value than stated in the list above.
Connectivity
| CONNECTOR / PIN | FUNCTION | COLOUR / CABLE COLOUR | ||
| VB OUT | Vehicle battery out | WHITE MOULDING | ||
| 1 | Battery + | Brown/Green | ||
| 2 | Battery + | Brown/Green | ||
| 3 | Battery Ground | White/Orange | ||
| 4 | Battery Ground | White/Orange | ||
| VB IN | Vehicle battery in | BLACK MOULDING | ||
| 1 | Battery + | Red | ||
| 2 | Battery + | Red | ||
| 3 | Battery Ground | Black | ||
| 4 | Battery Ground | Black | ||
| FRIDGE OUT | Fridge power supply | GREEN MOULDING | ||
| 1 | Fridge Permanent | Not Currently Used | ||
| 2 | Fridge Permanent | Not Currently Used | ||
| 3 | Fridge D+ | Red/Yellow | ||
| 4 | Fridge D+ | Red/Yellow | ||
| FRIDGE OUT | Fridge power supply | BLACK MOULDING | ||
| 1 | Low D+ | Orange/Yellow | ||
| 2 | not used | |||
| 3 | Fridge Ground | White/Black | ||
| 4 | Fridge Ground | White/Black | ||
| TOWING/VLM5/VLM7 | Tow & rear lights supplies | WHITE MOULDING | ||
| 1 | Tow Ground | Not Currently Used | ||
| 2 | Tow + | Yellow | ||
| 3 | Tow D+ | Red | ||
| FIAT IN | Signal inputs | RED MOULDING | ||
| 1 | not used | |||
| 2 | Marker light signal | Purple | ||
| 3 | Unlock | Black/Red | ||
| 4 | Lock | Red | ||
| 5 | Ignition (+12V) | Blue | ||
| 6 | Engine run (-ve) | Brown/White | ||
| TO PSU | user circuits | WHITE MOULDING | ||
| 1 | Low D+ | Orange/Yellow | ||
| 2 | Marker Light Power | Yellow/Black | ||
| 3 | Unlock | White | ||
| 4 | Lock | Green | ||
| 5 | Ignition (+12V) | Blue | ||
| 6 | Engine Run (-ve) | Brown/White | ||