Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Electrical Help

Hello,

My 2015 Morgan 3 Wheeler w/9800 miles has lost turns signals, hazard lights, tach light and seat heaters. I have checked all fuses and swapped relays with no change in symptoms. I've pull the rear dash cover plate and inspected all connectors with no issues found. There is no evidence of rodent activity, moisture, or shorting. The Morgan is garage kept at all times and meticulously cared for. Headlight, high beams, horn, and speedo functions work perfectly. This seems an odd pairing of failures. Any assistance would be greatly appreciated.

Thanks,

A loadpro (sold on Amazon) is a very useful tool to help you here. It connects to a regular multimeter and acts as normal set of leads as well as it can apply a load (believe 250ma) to check integrity of entire circuit when loaded. Basically, it can really help with finding where the extra resistance in the circuit is. Just measuring resistance unloaded in a circuit will very likely mislead you. There’s ways to do voltage drop testing with a multimeter alone but it is more complicated. When dealing with these kind of issues here are my steps:

1. Check battery voltage loaded to ensure 12v. Making sure battery has some juice in it.
2. Disconnect connector of component with issue. Unloaded, check there is battery voltage. If there isn’t, you’re dealing with an open somewhere. Load the circuit and ensure there is still ~12v. Less than 500mv drop is probably ok; anything more means you have high resistance somewhere. Trace down the high resistance disconnecting and loading with loadpro to narrow down where the high resistance is. Don’t forget the ground. If all of these components share a ground I’d probably start there first. Good luck.

Optional would be to use back probes to not have to disturb connector but they’re not mandatory. There’s a chance the high resistance is within the connector and back probes can catch this without disturbing things.

Higher level optional is a Power Probe. Those things are golden but can be dangerous (i.e. fry an engine computer) if the user isn’t fully aware of what they’re doing. It’s basically a multimeter and a 5/12v power supply all in one. There’s other useful functions to it as well.

Have a look at the parts manual MM which contains wiring schematics. You want the chassis loom for models on and after 2014. You will see after the main 50 amp fuse (check seating of this) there is a splice (bombtail) of eleven red cables to share battery feed. One of these, R29, feeds the ignition switch. Others supply the first four fuses (1 - 4) with keep alive feeds. These in turn supply side lights, horn, hazards and a feed to instruments.

As a start check main battery cables including chassis connection. Then bombtail for presence of +12 volts and again before and after each of the first four fuses, comparing with voltage directly at battery as they should get very similar. Unlikely to be a load issue but if for example you find output of fuse 2 is at expected 12 volts then operate horn (same circuit as hazards) to see if it works or if voltage at fuse collapses. The bombtail is located on the main loom 50mm after the split to TSM/headlamp unit and fuse cluster.

The feed out from ignition switch is a green/yellow cable to another bombtail feeding six similar colour cables, one of which feeds fuse 20 exclusively powering heated seats. Again you could check for presence of +12 volts (with ignition on) before and after fuse although it appears to be a separate stand alone issue.

Given this info you should be able to trace battery power all the way to failed circuits to find culprit(s).