How to install coolant temp warning light on a 470 with high temp alarm ?

[Rake722]

Hi all, hope this is the right place for this question

I have a mercruiser 470 that has the OEM low oil pressure / high coolant temp alarm fitted already.

i have successfully installed an oil pressure east Inv light and wanted to also install a coolant high temp warning light too.

can anyone advise how to connect this coolant warning light please ? The coolant sender has 2 poles, I do also have a second coolant sender installed but not connected.

i can’t quite understand how and where to connect the warning light.

thanks in advance

 

[Bondo]

Hi all, hope this is the right place for this question

I have a mercruiser 470 that has the OEM low oil pressure / high coolant temp alarm fitted already.

i have successfully installed an oil pressure east Inv light and wanted to also install a coolant high temp warning light too.

can anyone advise how to connect this coolant warning light please ? The coolant sender has 2 poles, I do also have a second coolant sender installed but not connected.

i can’t quite understand how and where to connect the warning light.

thanks in advance

Ayuh,...... Just wire the light in series with the alarm

 

[Rake722]

Thanks Bondo, can you be a little more specific about how to wire it in series ?

i sent one spade on the light to earth and the other to the I terminal where the alarm is wired to and that didn’t work so moved it to the S terminal and that still didn’t work

thanks

 

[Bondo]

i sent one spade on the light to earth and the other to the I terminal where the alarm is wired to and that didn’t work so moved it to the S terminal and that still didn’t work

Ayuh,..... On What,..?? Where,..??

You already have an alarm, Right,..??
If so, remove it's ground wire from the ground point, 'n attach it to one lead on the light, 'n the other lead on the light back to the ground point,......
That's in series,....
Or,....
Attach one lead from the light to the switched wire to the alarm, 'n the other to ground,.....

Either way, they'll both go on at the same time,....

 

[Rake722]

Thanks for that bit the alarm doesn’t seem to have a ground point. It’s a small black cylinder with 2 wires. One goes to the I terminal on the temp gauge and the other to the oil pressure switch on the engine ?

 

[Bt Doctur]

you better off keeping an eye on the temp gauge and doing the required service .By the time the light comes on you blew the head gasket to pieces

 

[Rake722]

I have this one

https://www.marine-surplus.com/prod...-warning-buzzer-alarm-assembly-kit-816492a15/

 

[Bondo]

Thanks for that bit the alarm doesn’t seem to have a ground point. It’s a small black cylinder with 2 wires. One goes to the I terminal on the temp gauge and the other to the oil pressure switch on the engine ?

Ayuh,...... The switch provides the ground,......

 

[Rake722]

I thought it only grounds on low oil pressure ?

 

[Bondo]

I thought it only grounds on low oil pressure ?

Exactly, which lights the light, 'n sounds the alarm,.....

 

[Rake722]

Done - I was being dumb last night - disconnected ground to oil sender, inserted red from light in one side and black from the light to the other side of the ground connector.

 

[Scott Danforth]

BTW, by the time the temperature rises 10 degrees (before the switch trips), the head gasket has been spit.. watch your gauges.

 

[Rake722]

BTW, by the time the temperature rises 10 degrees (before the switch trips), the head gasket has been spit.. watch your gauges.

On with that Scott. Currently the gauge is sitting just past 180.
I am not sure if the sender is matched to the gauge though.

 

[Scott Danforth]

180 is high. Confirm with an IR thermometer

 

[Rake722]

Yep thats the plan, I had installed Faria gauge and temp sender and then replaced the faria with a period or original style Detmar gauge - the Faria gauge read just below 175 - the detmar just over 180

I do actually have a digital gauge and thermocouple for very accurate readings but I have yet to install them.

 

[Rake722]

Just had a thought, - when installing the alarm kit, do you use another temp sender additional to the existing one for the high temp alarm or do you hook the kit up to the existing one ?

 

[Bondo]

Just had a thought, - when installing the alarm kit, do you use another temp sender additional to the existing one for the high temp alarm or do you hook the kit up to the existing one ?

No, you need a hi-temp Switch, not a sender for the alarm,.....

 

[Rake722]

No, you need a hi-temp Switch, not a sender for the alarm,.....

Does that switch go alongside the existing sender or does it replace it ?