tracking down a bad circuit

View attachment 93784My engine room blower on port isn't coming on with ignition, starboard is working fine


I wired it directly and it works


looking at the wiring diagram it goes thru what I think is relay.



How can I find that relay among a zillion others

I would follow the positive wire back from the blower.

First, verify there is no voltage at the blower motor. If you measure 12 volts maybe the blower motor failed?

If you have no voltage you can use a signal tracer. Clip on the tone generator at the Blower motor. Use the wand to trace the wire back to the relay. If you know where the relays are located use the wand to find the correct relay.

You can get a signal tracer for around $20

I use a tone/probe type tracker for that. None of mine are top dollar. They are whatever cheap one I got nearby whenever I needed one and didn't have one handy.

Here are some sources:
-- https://www.homedepot.com/p/Sperry-Lan-WireTracker-Tone-and-Probe-Wire-Tracer-ET64220/202520187
-- https://www.amazon.com/Extech-TG20-Wire-Tracer-Generator/dp/B00APD16D2

Basically, turn the breaker off to be safe, attach the red wire to the blower wire at the blower, then check each of the relays with the probe to see which one "rings". You can also follow the wire, and refind it after obstructions with the probe.


Depending upon the situation, hooking up the black wire will be helpful or not. The easiest way to tell without over thinking it is to see if it traces well a few inches down without it. And, if not, add it and see if it is better.

Got a cheapy tone tracer too. Freakishly simple and effective. Sometimes though, you just gotta pull down a wire race, put your mittens on a wire and see where it goes.

ok, I'll give that a try today

+1 on the tone tracer. I had to use that to track down where they'd put a fuse for the anchor windlass. It was only by accident that I finally found it. We just couldn't determine where it went after it went behind the generator. I happened to have my (very sweaty) hand on the exterior of the metal box that had some other switches on it. I happened to press the probe button in my other hand... and heard the deedle-deedle-deedle of the probe! Turned out they'd buried a fuse BEHIND the panel.

I've used the probe for countless other circuit traces in the past (houses, AC, speaker, networks, etc) but this was, hands-down, the most satisfying result.

Looking at that circuit it appears they're tripping the relay with the same positive that powers the fuel gauges? Is the associated fuel gauge display for that side's blower also powering up?

And let's not forget to ask the obvious question, has there been any other work done anywhere else on the boat (that may or may not have involved wiring)?

I to would use the tone tracer works good have had to use it on my boat. I bought one to keep on the boat.

Greetings,
Mr. l. Check your ground connection and all connections, for that matter but check the ground first.

Is that a relay, there is no ground on it and it is different than the other relays shown, can it be some sort of resetable breaker?

RT Firefly said:

Greetings,
Mr. l. Check your ground connection and all connections, for that matter but check the ground first.

Click to expand...

You stated that you wired it directly. Just wire the positive side directly. If it doesn’t work you have a ground issue as RT stated. If it does work focus on the positive side / relay.

Found the relay the beeper made it easier two of the same type were side by side, I pulled the other relay and star blower failed, so I know for sure I have it located


It's 4 pin relay, the writing on cover of the relay is not legible?



two heavier wires and 1 lighter gauge, I assume that one is from ignition.


I'll stop by Napa in the morning to if they have one

Pull the gas engines and install diesel engine or engines. Then you don't need a blower! Sometimes simpler than tracking a bad wire..

Good luck, you will love the diesels

pete

First of all it is diesel, never heard of no blower

Diesel fuel doesnt have explosive fumes and diesel, so there is one fewer reason to have active blowers for ventilation before it can be achieved passively underway, if not even while underway.

That's not to say that there arent reasons to have a blower or blowers with diesels, just that preventing Kaboom! isn't one f them.

Usually with a diesel a blower is used either to supply combustion air or to remove heat from the engine room during and after a run.

Are your blowers "innies" or "outies." Reason I ask is as a new boat owner I ran the single EXHAUST blower ("outie") in the old trawler whenever the engines were running, and I was constantly burning out those 12-Volt POS Jabsco units. I learned to not run it except when the engines were shut down because it was trying to exhaust the air the engines were trying to inhale. Duh.

Most folks avoid an "innie" blower as any exhaust leak would be fed into the living spaces.

When stationary the blower might move engine space warm air into the cabins as a fall evening heating solution .

FF said:

Most folks avoid an "innie" blower as any exhaust leak would be fed into the living spaces.

When stationary the blower might move engine space warm air into the cabins as a fall evening heating solution .

Click to expand...

Last thing I would want would be to move any hydrocarbon laden air from the ER to the cabin.

Inward blowers should never be needed in the design of a pleasure craft engine space, but I am hard pressed to think of a ship I was ever on without them.

Ships I have been on tended to have airtight exits from machinery spaces...then again all but a few were "combatants" at some level of build.



I thought that the constantly manned spaces within machinery spaces were positive pressure to stay clear of smoke/fumes and that principle was for safety beyond war fighting capability.

psneeld said:

Ships I have been on tended to have airtight exits from machinery spaces...then again all but a few were "combatants" at some level of build.



I thought that the constantly manned spaces within machinery spaces were positive pressure to stay clear of smoke/fumes and that principle was for safety beyond war fighting capability.

Click to expand...

Not much to argue with there, and because the engineering spaces in ships tend to be (but are not always so in practice in the civilian world) sealed off from living spaces, you can blow a ton of air in there and not fumigate the living spaces.

BTW, for the old Navy salts here, from 1996 to 2012 when I was regularly riding gas turbine powered warships as a Navy contractor, I began to see unmanned main propulsion spaces except during general quarters. Aft steering is never manned except at GQ, much different than in my day when it was always manned (see McCain collision).

Swap your starboard relay to the port side and test on ignition. If it functions it is simply your relay and if not, tone out your hot at relay and work your way towards the blower if you have 12v up to that point. suerte

I would have but couldn't find the relay, so toning it out led me to the relay, changed it all is good

Excellent! Yeah, I glossed over your initial post... On the upside, now that you have identified those relays you can figure out and label the others from your schematic for the future. Glad you got er worked out.