Temperature Gauge Not Functioning Mercruiser Alpha One, Help.

[1985 Century Mustang]

I recently removed the engine to rebuild my transom. Today I finally took it out and noticed the temperature gauge isn't registering at all. Could I have screwed up a wire? The wire on the sensor on the block is intact. What steps do I need to take to test it. I am getting voltage at the gauge itself.

 

[alldodge]

What color wire is on the sensor?
Should be Tan with no stripe

 

[1985 Century Mustang]

I grounded the temp sensor wire to the block, turned the key on and no movement. I also ran a wire to the temp sensor and grounded it, no difference.

 

[1985 Century Mustang]

What color wire is on the sensor?
Should be Tan with no stripe

It definitely looks tan. However, I'm not sure about a stripe, as I'm away from the boat currently.

 

[1985 Century Mustang]

Any pointers anyone?

 

[matt167]

Well from 1985 you can’t rule out a gauge that took a crap. What I would do is get it up to temp and check the sensor for function

 

[1985 Century Mustang]

Well from 1985 you can’t rule out a gauge that took a crap. What I would do is get it up to temp and check the sensor for function

It actually worked flawlessly till I put the engine back in the other day. So when I went out today finally, it wasn't functioning.

 

[1985 Century Mustang]

Well from 1985 you can’t rule out a gauge that took a crap. What I would do is get it up to temp and check the sensor for function

Thanks, I'm buying a new gauge and sensor.

 

[alldodge]

It might be the engine 10 pin connector.

First see if there is 12V on the gauge. Next ground the sensor terminal on the gauge to see if it pegs

 

[1985 Century Mustang]

It might be the engine 10 pin connector.

First see if there is 12V on the gauge. Next ground the sensor terminal on the gauge to see if it pegs

Thanks, that's what I was pondering also, especially because I needed to plug it back in after I installed the engine, good call. I'll check it today.

 

[1985 Century Mustang]

It might be the engine 10 pin connector.

First see if there is 12V on the gauge. Next ground the sensor terminal on the gauge to see if it pegs

Thru further inspection, I noticed that 3 pins came off the male end of the 10 pin harness connector and went into the female end on the 10 pin connector, apparent they were loose.

Can I just put them back into the male end, and if so what can I use to keep them in place so it doesn't happen again.

 

[1985 Century Mustang]

It might be the engine 10 pin connector.

First see if there is 12V on the gauge. Next ground the sensor terminal on the gauge to see if it pegs

Yes I got a reading of voltage from the gauge itself, but im not 100% sure if it was 12v , but it could have been possibly.

So do I take a jumper wire off a hot lead on the gauge and ground it, to see if it pegs?

 

[1985 Century Mustang]

A few pins that came off of the male part of the harness and are now stuck in the female end, can they be removed and then be put back into place on the male end, if so do I just push them back in? And would I need an adhesive or solder them in back into the male end? Please advise, Thanks

 

[alldodge]

12V power is there but the Tan wire going back to sender is missing.

So far as the pins you have a few options
Carefully pull pin out and try to get it started in location, then carefully push back together

Remove pins totally from both connectors, solder together and reinstall rest of the connector

Get a new male pigtail and splice all wires from old to new. Link below is Hardin marine but think if you look around you can find cheaper or even used out of another boat
https://www.hardin-marine.com/p-132...-pigtail-mercury-plug-instrument-side-12.aspx

 

[1985 Century Mustang]

This is my harness.

 

[04fxdwgi25]

That could be a problem. I would seriously consider a new harness / replacing the plug with one from a donor harness.

 

[Chris1956]

Agreed, the connector is bad. If you can find a replacement connector, you could use some waterproof butt connectors to graft it to the old wires.

something like thise

NIB Mercruiser 2.5 to 8.2Lit Ignition Wire Harness Pigtail Boat End 9-Pin 6118-1 | eBay

Find many great new & used options and get the best deals for NIB Mercruiser 2.5 to 8.2Lit Ignition Wire Harness Pigtail Boat End 9-Pin 6118-1 at the best online prices at eBay! Free shipping for many products!

www.ebay.com

 

[matt167]

A new complete bulk harness is $200. ( not engine harness or gauge harness ). That’s what I would do. It just plugs in on both ends

 

[1985 Century Mustang]

A new complete bulk harness is $200. ( not engine harness or gauge harness ). That’s what I would do. It just plugs in on both ends

Can u send a link?

 

[matt167]

I’m at work I’ll find it later tonight. I literally replied out the door this am