I recently purchased a fresh water 2003 38 Open with low hours. Starboard tach starting to fail and then the port tach failed including the hour meters. Boat has Glendenning system too. Electrical contractor felt synchronizer gauge was causing a short and both tachs worked for awhile after unplugging. Now both tachs are failing again. Any ideas? or recommendatiosn?
What type of failing? Are they bouncing around? If so, that is probably a ground issue as many have the same problem, intermittent ground. Let us know so we can help a little more.
I have a 35' Open, I am having the same problem with the tach's that you have explained. Yesterday we made a 100 mile run on the Great Lakes and they would work intimately, but most of the time not, and nearly never steady, "always both at the same time" I have suspected that it is a ground, but with my lack of knowledge in this area I don't know where to look for the grounding point.
All the yellow wires behind the helm are DC ground points. All yellow in the bilge are DC ground points. I would start at the batteries and make sure they are connected without issue, same for starter, alternators, regulator, ground on engines and battery charger. Then move to the Cummins alarm board behind the helm. Found alot of issue with those connections as they were corroded and not making great contact with intermittent alarm errors. Then move to the back of the tachs and the rest of the wiring grounds for the gauges.
When you are cleaning up your electrical connections put some "Corrosion Block" on the lugs, connectors and terminal boards. It comes as a grease or a liquid. Both work well and prevent future problems. Available at West Marine. Capt. George
Diesel tachs use a magnetic pickup, usually off the flywheel. If the sender is adjustable make sure the gap is correct. It is VERY critical. Capt. George
Thank you very much for all of your responses, Our 2000 35' Open with Cummins 370s is being pulled today for winter heated storage. I will add your recommendations to my winter of list items that need attention.
This is a great forum with participating individuals that have and share a ton of knowledge. Thank you,
John
I agree that both gauges failing at the same time is likely a grounding/wiring issue. I would do as suggested and go through all of the grounds. Capt. Georges suggestion of Corrosion Block is an excellent one! I dose all unpainted metal parts and electrical connections with the clear spray Corrosion Block. If you have the mechanical Glendinning engine synchronization system, I would definitely check the connections there.
Thanks Chris, I do have Glendinning synchronizers. Our previous boat was a 42' Grand Banks Classic and we had a plastic gear break on the tach drive mechanism on the port engine while the synchronizer was engaged, when the tach went to 0 the throttle went full open, this does not do that. It runs fine with the synchronizer on. So I probably would not thought of the synchronizers as being a possibly source of the problem.
I recently purchased a fresh water 2003 38 Open with low hours. Starboard tach starting to fail and then the port tach failed including the hour meters. Boat has Glendenning system too. Electrical contractor felt synchronizer gauge was causing a short and both tachs worked for awhile after unplugging. Now both tachs are failing again. Any ideas? or recommendations
Thanks everyone for your input. After 4 attempts from the same electrical contractor and your advice we solved the issue. It must have been one of the yellow ground connections behind the helm unit. The small synchronizer gauge is still unplugged so I might have had two issues causing complete failure of both tachs. I am reluctant to even replace this gauge as the Glenndenning system works great. I will keep anti-corrosive (T-9) on the grounds from this point forward.
![[-]](https://www.tiaraownersclub.com/forum/images/netpen-pro/collapse.png)
