[SEMIJim]

Well, we took possession of our '94 Mariah 182 Barchetta today .

Taking her around from launch to slip, noticed we're getting no engine temperature reading. She was re-powered with a re-built Mercruiser 4.3L V6 due to the original having a cracked block. I suspect that the seller neglected to reconnect the temperature sender. So: Where is this located on the engine and, if this is standard for Mariah, what colour wire am I looking to connect to it?

Secondly: If I find the wire and sender are already connected, how can I trouble-shoot this? I.e.: Measure the resistance of the sender with a multimeter? What range of resistance should I see? If I put a voltmeter between the wire that's supposed to connect to the sender, and ground, should I see 12VDC? Something else?

Thanks,
Jim

[WetWilly]

Hi Jim,

Originally Posted by SEMIJim

If I put a voltmeter between the wire that's supposed to connect to the sender, and ground, should I see 12VDC?

Yes, or close to 12VDC. The sender varies the resistance to ground so there should be full voltage to the sender. If you're not getting any or a low voltage to the sender, check the terminal labeled "SEND" on the back of the gauge for voltage. If none, check for voltage on the terminal labeled "+12V" if there is voltage here, your gauge is bad, if there is no voltage here, you probably have a blown fuse somewhere.

The Merc 4.3 Manual (section 4) shows how to check the gauge (Pg 4D-2) and sender (Pg 4D-6).

The sender should be located on the starboard side of the thermostat housing or on the intake manifold just below the housing and the wire coloring should be "Tan".

Good luck,
WetWilly

[SEMIJim]

Thanks, WW! Everything I needed to know

The gauge worked before the re-powering, so I'm pretty sure I'll find it's simply
disconnected.

Jim

[SEMIJim]

Problem solved!

There are two senders on the thermostat housing: One on the starboard side and another on the port side. (More on this later.) They'd gotten the connections backwards on re-assembly, obviously.

There are four (4) connections on the back of the water temperature display. It's the left-most of the lower three, as you're looking from the back of it, IIRC, that'll have the tan wire on it. I only measured 6.4VDC and change on that terminal. I'm pretty sure the sender was disconnected at the time, and I measured the same voltage at the sender end of the wire, with it disconnected from the sender.

What is that sender on the port side, to which the tan-with-blue-stripe wire connects? I measured zero voltage on that wire. (I didn't measure that sender's resistance.) That sender on my engine is partly red.

Thanks again for the help, WW!

Jim

[dudders]

The Merc 4.3 Manual (section 4) shows how to check the gauge (Pg 4D-2) and sender (Pg 4D-6).


Hey Willy, I cant find this manual, can you direct me to it mate?
That or send me a pair of #2 reading glasses eh?

CHeers
Tony

[WetWilly]

Originally Posted by dudders

Hey Willy, I cant find this manual, can you direct me to it mate?
That or send me a pair of #2 reading glasses eh?

No problem Tony, here ya go,click here and look at the "GM43V6-ElectricalSystems" on the pages I posted above.

Hi SEMIJim , looks like the mechanic switched the alarm overtemp and the regular temp wires around. Bet the other wire was a Tan/Blue one right?

WetWilly

[SEMIJim]

Originally Posted by WetWilly

Hi SEMIJim , looks like the mechanic switched the alarm overtemp and the regular temp wires around. Bet the other wire was a Tan/Blue one right?

Apparently so. Yes, the other is tan with a blue stripe. I'll be buggered if I understand how it works, being as I measured no voltage on the end of the wire.

Can I ground that wire to test the alarm circuit?

Thanks,
Jim

[dudders]

Fantastic, this is going to be very helpful Willy, I appreciate your help mate.
Cheers Tony

[WetWilly]

Originally Posted by SEMIJim

Apparently so. Yes, the other is tan with a blue stripe. I'll be buggered if I understand how it works, being as I measured no voltage on the end of the wire.

Can I ground that wire to test the alarm circuit?

Thanks,
Jim

Hi SEMIJim, Funny that you don't see voltage on the Tan/Blue wire, I suspect your buzzer is bad. locate the alarm buzzer either under the dash or behind the stereo panel and you'll find two wires, the Tan/Blue and a Purple wire, the Purple wire should have 12 volts when the ignition is turned to the "on" position, if not, trace it back to see if there is a connection issue or an inline fuse although the manual doesn't show one (4E-10).

Now if you did have voltage then the answer would be "yes", grounding the tan/blue wire to the block (ground), the alarm should sound (assuming the alarm buzzer is still functioning). The alarm circuit has a water temp (model specific), oil pressure and outdrive oil level sensor and all these have Tan/Blue wires attached to them.

With the motor offand cool, the water temp sensor should register open and so will the outdrive oil level sensor if the oil level is where it's supposed to be and the oil pressure sensor will register as shorted.

You should get the alarm warning when you first turn on the ignition and start your motor, then the alarm should go out shortly after the motor fires up when the oil pressure sensor receives enough pressure to go from a shorted to an open state.

Originally Posted by dudders

Fantastic, this is going to be very helpful Willy, I appreciate your help mate.
Cheers Tony

My pleasure mate!



WetWilly

[SEMIJim]

Originally Posted by WetWilly

You should get the alarm warning when you first turn on the ignition and start your motor, then the alarm should go out shortly after the motor fires up when the oil pressure sensor receives enough pressure to go from a shorted to an open state.

Ah, I'm definitely not getting that. Oh boy: Another maintenance point!

(The bilge pump isn't doing anything, either, either via the float switch in the bilge or the manual switch on the panel.)

Btw: Assuming the buzzer's bad, any pointers on what I need to replace it with?

Thanks,
Jim