Some gauges are bigger than others. And on my Morgan dashboard these are the 100mm instruments behind the steering wheel. The old tachometer was a cheap replacement and stopped working at least a couple years ago. So a replacement was necessary anyway. There are two reasons why I also decided to go with a new digitial Smith speedometer. Main driver was the fact that I installed a Brantz BR4 sensor for my Brantz International 2 Pro. Although classic car rallyes seem far away with Covid – the intention is to do a couple with the Morgan.
After I got the sensor I realized that the speedo cable does not fit properly and extended the cut-out in the gearbox tunnel. Even though the cable is covered unter the gearbox leather -there is a noticable bump under the cover. And after I had it all installed with the correct speedo cable – I noticed that the speedo needle still quite often “jumps”. I checked both cable ends and the gearbox side is new and perfect. The problem wasthe angle behind the dashboard – The speedo worked well when I had it just laying on passenger floor. Instead of getting an even longer speedo I choose to go digital. While they could not promise that the setup works – the Brantz support team were so kind to let me know that the BR4 is NPN sensor. The white sensor cable attached to pin6 (white/black cable) on the Smith input should work. And what can I say: it works like a charm.
The Brantz unit will be mounted when needed with a bracket inside the new glove box. To make it easy to remove, I added a plug on the side of the glovebox (along with a dual USB charger). Smith speedo and the Brantz rallymeter share the same sensor signal. The only thing I had to change is that the sensor (red cable) permanently gets 12V. The default plug cabling is that the sensor only gets power if the Brantz unit is switched on. In theory not difficult to change – but I already connected the Brantz cables to the loom back in January and wrapped them well. If I want to do it correctly – I need to take the dashboard (that just went it) out again….
This will making fixing a few other things easier as well. I wired up a standard Lucas toggle switch along with two P600A diodes as hazard switch. When I reconnected the battery the newly added indicator fuse blew. As the diodes were the last thing I added – I expected them to be the problem. It took me 2 hours (and 3 more fuses) to trace down the problem. Well, actually I should say that the problem is gone – and I am still not 100% sure if the root cause was really a broken indicator bulb holder. At that stage I still hoped to fix everything with the dashboard in-place and just removed the new tacho. This allows easy access to the 5 bulbs between the gauges. I had two spare bulb holders – and the short-circuits issue is gone. However, the old Lucas toggle switches don’t work reliably and two of them need to be replaced. The Off/OnA/On toogle switch for the heater needs to be turned around.
The smaller 52mm Smith instruments all got new chrome bezels, seals and a bit of cleaning. Even though I tried to be as careful as possible the Voltmeter and fuel gauge needles now stick a little and need further attention. The last problem of the day is the new Lucas indicator stalk. The right indicator doesn’t work. Fortunately, I had the old one still around for testing – and the multimeter quickly revealed that there is no signal between the green/white and lightgreen/orange input cable when it is engaged.
So the task list for tomorrow evening is clear – hopefully I will be able to finish it.
Fixing C6622 
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