Switches on Dash...Please Help!

Hi guys, I really need some advice here!

I'm having an intermittent problem with my dash switches. It started with the blower not working...now it's hit or miss with everything on the dash (strictly the switches, not the speedometer, fuel, oil, etc, those all work fine).

Last week I troubleshot the blower, getting 12vdc to the switches, ohmed the yellow wire from the switch to the blower and is good. Ohmed the black wire from the blower to ground, that too is good. Swapped the wires with the bilge switch and blower didn't work still, so thought I ruled out a faulty switch. Cleaned harness connection by steering wheel.

Now, when I go out and everything is cool and has not been running, all switches work as intented. Today, I started to the boat (switches working before I started it) and as you can see from the pics below, when it's not working properly, I press CT LT switch and the bilge, blower, and CT LT all light up, but nothing turns on. Also, the other pic shows the horn being pressed and the same 3 lights lighting up, but no horn (blower, lights, or bilge either).

Went out about 4 hours later and everything was working fine again. I started thinking this was a blower wiring problem, but am thinking it is def. something else! Does anyone have schematics for this or any suggestions? Should I go buy some new switches and pop those in?

I have a 1995 Mariah Talari 180 (w/ a 3.0L LX Mercruiser). HULL ID MAB10038F595 if that helps.

I had the boat out for the first time since I purchased it and I was unable to use the blower, bilge pump, etc and I won't take it out until I get this nailed down.

Thank You!
-Tim

Re: Switches on Dash...Please Help!

Are thes circuits all attached to common buses? Is so, check from the bus backwards. Sounds like a loose connection (vibrates on and off). Best to check your path when its NOT working.

Re: Switches on Dash...Please Help!

Yes, they are all attached to the same bus, even when it's not working properly, I still get 12vdc to the switches. They are all in parallel and start at the far left with the blower and work to the last switch, the horn.

Re: Switches on Dash...Please Help!

Hi Maxum,
Without a schematic diagram, it's difficult to help you troubleshoot. The gauges aren't affected likely because they are normally part of the engine wiring system and not the boat's wiring system. At this point, I'm suspicious that there is a poor negative connection somewhere, not necessarily at the negative battery terminal but perhaps at a major point common to the pump, the blower, the horn and the CT lites. What I think you have is current flowing correctly through the switches and then through each of these loads, but then intermittently obstructed at a dirty, loose or heat damaged negative connection. The current might then flow through any alternate negative paths such as the negative connection points at the switch indicator lights. These alternate negative paths are not adequate to carry enough current to drive the pump, blower or horn, but could cause the indicator lights to turn on. - Grandad

Re: Switches on Dash...Please Help!

What is that mounted on top of the switch panel? Check for a nicked wire near where those screws go through.

Re: Switches on Dash...Please Help!

When the result are completely irrational, (As in, I press the horn switch, and three light on different switches light, but the horn does not work) the problem is a faulty Ground 99.9% of the time.

It is also likely that you have ONE problem and not four.
Fix the one and the others will resolve themselves.

Boat (and Auto) electronics are High current, Low Voltage circuits that require Low Resistances to operate.
High currents and low resistances are notoriously difficult to measure casually.
When you "Ohmed" the wire from the switch to the blower you need to realise that as little as ONE ohm in that circuit would be considered a faulty circuit.
The resistance of just the meter leads alone, is close to unacceptable.
These type of measurements need to be done in an indirect way.

Lets get the Blower working!
The blower draws about 5 amps.
One single ohm of loss will make the circuit loose 5 volts. (E=I x R)
So 12 volts will appear as 7 volts AFTER the fault. (Hold that thought!)

Power up the blower so that it SHOULD be working. Switch on!

If at any time you do not see at least 12 volts, you just found the problem!
Make the following measurements. (Just Humor Me!)

Pos Meter lead on Battery Pos Terminal Post.
Neg Meter Lead on Neg Battery Terminal Post. (Not the Battery Clamp, The actual Post!) 12v?

Pos Meter lead on Battery Pos Terminal Post.
Neg Meter Lead on Engine Block. 12v?

Pos Meter lead on 12v common feed to Switches.
Neg Meter Lead on Engine Block. 12v?

Pos Meter lead on Blower Switch output. (Yellow wire)
Neg Meter Lead on Engine Block. 12v?

Pos Meter lead on Pos Wire at Blower.
Neg Meter Lead on Engine Block. 12v?

Pos Meter lead on Pos Wire at Blower.
Neg Meter Lead on Neg Wire at Blower. 12v?

If you got this far without a failure it is a bad blower. (Not Likely!)

Re: Switches on Dash...Please Help!

UncleWillie said:

When the result are completely irrational, (As in, I press the horn switch, and three light on different switches light, but the horn does not work) the problem is a faulty Ground 99.9% of the time.

It is also likely that you have ONE problem and not four.
Fix the one and the others will resolve themselves.

Boat (and Auto) electronics are High current, Low Voltage circuits that require Low Resistances to operate.
High currents and low resistances are notoriously difficult to measure casually.
When you "Ohmed" the wire from the switch to the blower you need to realise that as little as ONE ohm in that circuit would be considered a faulty circuit.
The resistance of just the meter leads alone, is close to unacceptable.
These type of measurements need to be done in an indirect way.

Lets get the Blower working!
The blower draws about 5 amps.
One single ohm of loss will make the circuit loose 5 volts. (E=I x R)
So 12 volts will appear as 7 volts AFTER the fault. (Hold that thought!)

Power up the blower so that it SHOULD be working. Switch on!

If at any time you do not see at least 12 volts, you just found the problem!
Make the following measurements. (Just Humor Me!)

Pos Meter lead on Battery Pos Terminal Post.
Neg Meter Lead on Neg Battery Terminal Post. (Not the Battery Clamp, The actual Post!) 12v?

Pos Meter lead on Battery Pos Terminal Post.
Neg Meter Lead on Engine Block. 12v?

Pos Meter lead on 12v common feed to Switches.
Neg Meter Lead on Engine Block. 12v?

Pos Meter lead on Blower Switch output. (Yellow wire)
Neg Meter Lead on Engine Block. 12v?

Pos Meter lead on Pos Wire at Blower.
Neg Meter Lead on Engine Block. 12v?

Pos Meter lead on Pos Wire at Blower.
Neg Meter Lead on Neg Wire at Blower. 12v?

If you got this far without a failure it is a bad blower. (Not Likely!)

Click to expand...

Good post! Everyone can use this sooner or later.

Re: Switches on Dash...Please Help!

Thanks Uncle Willie! I will get back out there this afternoon after work and check this out and post a reply tonight

Re: Switches on Dash...Please Help!

Thanks Grandad, I'm going to shimmy my way to the fuse panel and neg. bus bar tonight and clean all the contacts and check for anything loose as well as go through the procedures UncleWillie listed. Thanks! I'll be posting my results tonight.

Re: Switches on Dash...Please Help!

sschefer said:

What is that mounted on top of the switch panel? Check for a nicked wire near where those screws go through.

Click to expand...

That's where they mounted the fish finder...I did check for nicked wires and there were none. Thanks!

Re: Switches on Dash...Please Help!

Maxum88 said:

Thanks Grandad, I'm going to shimmy my way to the fuse panel and neg. bus bar tonight and clean all the contacts and check for anything loose as well as go through the procedures UncleWillie listed. Thanks! I'll be posting my results tonight.

Click to expand...

I would suggest you disconnect EVERY connection ONE at a time and re-attach.

I chased electrical gremlins and normally most problems are a result of corrosion. Some wires that feel tight and look tight might have a POOR connection.

A few cans of beverages........ some 150 sandpaper...... a can of contact cleaner and have at it. I would even remove fuses and lightly sand them too.

The biggest gremlins are the ones that live inside of relays. Most people can not see the corrosion inside a relay but, it does happen.

Re: Switches on Dash...Please Help!

Thank You all, Uncle Willie, Bob_VT, Grandad, Captain Kickback, and everyone else...following Uncle Willie's steps I found the following:

Pos Meter Lead on Pos Wire at Blower
Neg Meter Lead on Engine Block
Result: 11v when blower on, 12.36 when blower switch is on, but disconnected at the blower

Pos meter lead on Pos Wire at Blower
Neg meter lead on Neg Wire at blower
Result: 9.5v

There is a bus bar mounted on the bow by the battery that is copper, but has stainless posts and wires that were crimped but not with marine terminals. I started taking off the wires when I ended up just having to cut them because the nuts were rusted on. I found the one that was for the blower and sure enough, it was acting up again after just working. I took it off and connected it to the neg battery terminal and it was working again and measuring 12.36 vdc at the blower. See pic below for what I took off, going to West Marine for a new one tomorow. I am now convinced I will go through the fuse panel at the helm and clean it up as well.

Thanks again for everyone's help!
-Tim

Re: Switches on Dash...Please Help!

Congatulations! Good Job!

If you learned nothing else, Remember This ...

UncleWillie said:

When the result are completely irrational, the problem is a faulty Ground 99.9% of the time.

It is also likely that you have ONE problem and not four.
Fix the one and the others will resolve themselves.

Click to expand...

Re: Switches on Dash...Please Help!

Maxum88 said:

...There is a bus bar mounted on the bow by the battery that is copper, but has stainless posts and wires that were crimped but not with marine terminals.

Click to expand...

A Battery and a Ground Bus in the Bow of a Bowrider!
Who Wu'da thunk???

My guess is that was NOT installed by the factory.