Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Rev counter and now temp gauge

First drive on new tyres and the Plus 4 feels much better.

But the rev counter is still playing up - came back home at 3000rpm all the way, including at idle. Switched off and on and full deflection for rest of journey. And I have lost the temperature gauge.

Tried on the drive and rev counter still does its own thing - sometimes zero, sometimes full deflection, sometimes 6000 rpm and very occasionally showing the actual revs. With the temp gauge, on switch on it moves from the rest position perhaps 1mm and just stays there - registering below the scale.

And yes, I am waiting for the red light to go off before trying to start the engine.

Drives ok though!

Any thoughts before I take the dash apart???

Cheers
Nick

Try disconnecting the battery. Leave it 10 mins and then re-connect.
P

Hello Nick: Not sure the year of your Plus 4 but I would check for two things, poor earth connection and faulty voltage stabilizer. As voltage stabilizers are cheap it is worth just replacing it, assuming you have one fitted.

Thanks folks.

It's a 2012 build. Just moved it on and off drive. First time nothing on either gauge. Second time working rev counter and temp gauge.

I am going to add a fuse to the trickle charger so the battery comes off on Sunday. Then I'll open up the dash (again) and have a good look.
Dodgy earths may be to blame indeed. I know the temp gauge is run off that pesky control board behind the centre of the dash - I have a spare following my heater fan shenanigans so I may try swapping that out.

I am kicking myself for telling someone that I have had the car running reliably for a year now so it is sorted - clearly it didn't like that..... Today I could happily flog it to the first bidder!

Probably the immobiliser. Change the ignition key and should be remedied. Exactly same fault as on my 2012 plus 4

Thanks Dee Pee. Tried the spare key - tried it at least a dozen times and fine every time. So I'll try the spare for a while and see if that is indeed it. I have 2 spare keys so should be ok for a little while if that fixed it :-D.

Well at the MOA Cocktail Party in Sun Valley I bragged that I could get answers to any Morgan Problem! Wrong! As My informants have no or little knowledge of the Newer Morgans I don't have a clue. About 1970 is My limit.

I am with you. I had known how much electronicery there was on my Morgan, especially some of poor quality, then I would have probably bought an older car. Growing up in the 60s and 70s it was easyback then to fault find and fix a car.

My escapades with the circuit board behind the dash were exceedingly frustrating. It would be better if a proper wiring diagram was available - they MUST have such a thing at the factory, but not even my local dealer can get a copy. So we have to work with the parts book wiring loom - and that's even if the factory built the car to the spec. It's a struggle, and I have a degree in electronic and electrical engineering to fall back on!

Perhaps Dave W could rise to the challenge and write a sequel - Modern Traditional Morgan Electrics????

Nick. The circuit board behind the dash is notoriously unreliable. I had it burnt out 3 times and when it goes it burns the fuse which leave you without a speedo too. It was part of the impetus for me to change the dash because Borghi re-wires everything to eliminate the circuit board.

The problem with the circuit board is apparently that a lot of items, including the two speed heater fan, are earthed through the board and it is not robust enough to take it. The issue may have been complicated by the fact that I have aircon fitted.

I did finish up having problems with the new fuel gauge and temperature gauge both of which I have "temporarily adjusted" by adding parallel resistors in the circuit. In both cases there is too much resistance in the circuit to the sensors or between the sensors and the negative of the battery. My feeling is that this problem relates more to the new circuitry than the instruments themselves (which have been cross checked against the original) however I have not been able to get to the bottom of the problem.

To get back to your problem I am certain that there is a bad connection somewhere in your circuitry. Once the dash is off it is easy enough to check the power supply and the earth on both instruments. If they are both good the problem almost has to be in the line to the sensors. It can not be between the ECU and the engine or you would have problems with the engine running. The first thing I would do is to try unplugging and replugging, two or three times) the cable to the ECU, and perhaps also the MFU. It could simply be a poor connection between the connector and the pins on the ECU. Probably best done with the battery disconnected

Thanks Peter,

At the moment it is working with the spare key so I will keep an eye on it. I have had that board off a few times - in my case (related to the heater fan and the speedo) it was down to the flyback diodes being under specced (Dan at Krazy Horse found that for me) - those are replaced on the board that is in the car now, and I have just done the same on my spare board.

So I'll leave it for now, then dash off and test connections if it comes back. Then swap to my spare board of that doesn't fix it.

Nick