Moss Motors, Ltd

Sometimes all my gauges work great, and other times they don't. It seems the gas, rpm, and temp all seem to be connected to the same wire for this to happen. Anyone else come across this?

Thanks,

Chuck 

Yup, I'm sure that anyone owning a Brit car has experienced something like this at one time or another.  It reminds me of one of my favorite jokes...

"Why do the English drink warm beer?  Because they all own Lucas refrigerators"

.

Joke aside, all of the instruments will share a common ground and a common positive, so yes one connection can cause this.  A wiring diagram is very helpful here.

What your experiencing is an intermittent open circuit, technically not a "short".  The most likely culprit is a loose connection in the harness and to make matters worse, its probably behind the dash and the act of moving wires around to get at stuff stands a good chance of hiding the source from you.

The lucas wiring harness uses male bullets soldered or crimped onto the ends of the wires.  They are in turn joined to other wires via double ended female connectors.  These connectors are made from a plated sheet of hard rolled brass and are quite brittle and they will split with age.  They will look fine until you unplug them since the hard plastic insulator holds them in place.

You can try wiggling stuff under the dash to narrow it down, but you may need a helper to spot the gauges while you do it. If you do "get in the ball park", start unplugging and carefully inspecting the females for splits and replace them when you find them.

I have felt your pain and I hope you can track it down without a whole lot off hassle.

Best of luck

 

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-Michael

Here's a link that will help you troubleshoot.  http://www.advanceautowire.com/mgb.pdf

Electrical problems are my favorite!

Check for bad grounds....happens alot. 

 

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On their death bed, nobody ever said, "Gee I wish I'd spent more time at work!"

'68 Sprite 1275
'76 Midget 1500

Thank you, and I think I'll serve only warm beer at my house until I get the wiring fixed. That way maybe my drinking buddies will be more inclinded to help find the problem..... I've not checked under the dash a lot since buying the car, but will check there today.

 Any chance you would know what the green wire that runs the temp fans would connect to? It's on the inner passenger fender near the fuse panel. I don't think it goes to the fuses, and don't see a connector anywhere that looks like where it was connected. Seems to me it would go to a hot wire that is hot even when the car isn't running, so the fans will stay on to cool things doen a bit after the engine is off.

Thanks,

Chuck

mgcsaylor@verizon.net  Can help.  You are correct about it being hot wired and controled with a thermostat.  So regardless it needs to be wired hot all the tine.  One side of the fuse box should be that way.

What year is that car?

I'll look at the schematics and have an answer for you.

---

On their death bed, nobody ever said, "Gee I wish I'd spent more time at work!"

'68 Sprite 1275
'76 Midget 1500

Thanks! It's a 78B

Chuck

The schematic for your car is on page 25 (of 33), of that link I sent you.( http://www.advanceautowire.com/mgb.pdf ) The cooling fans are just left of center of that page -  - take a look.

According to the schematic, there is supposed to be a brown/white wire from fuse block terminal #5, through an in-line fuse, that runs to the thermostat.

The other side of the thermostat has a Green/Black wire that goes to a distribution connector to service the fans.

I hope this helps. It's tough at best to chase wiring harnesses from hundreds of miles away!

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On their death bed, nobody ever said, "Gee I wish I'd spent more time at work!"

'68 Sprite 1275
'76 Midget 1500

Hey Thanks! The diagram really puts things into perspective and I've found a few other things I need to change. The previous owner disconnected the ballast, so since i've got it may as well run new wiring and hook it up.

 I really appreciate you taking the time!!

Chuck