Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) 2001 +8 Temperature gauge

Alan, your 2001 +8 according to wiring diagrams doesn't have an old style instrument voltage regulator. The instrument signal grounds are directly shared with each other so unlikely to be an issue if other gauges displaying normally. There is a green/blue coolant temperature signal wire from instrument in dash loom that connects with same colour wire in main chassis loom and on to engine loom and likely to ECU. The coolant temperature sensor signal also feeds to ECU on green/blue wire but no further info due to missing intermediate wiring diagram.

As Tim suggests your issue is likely with the dash instrument itself although you could check wiring connections as above. A cheap infra red/laser temperature sensor could be used close to temp sensor to allay fears of engine overheating.