Temp Sender Audible won't go off

[Chavez1978]

I have read the sticky about checking the sensor wiring by grounding the wire, so I don't mean to ask a dumb question...but I'll ask anyways. I have a 5.7L Mercruiser V8. I replaced one temp sender and now my thermostat reads around 130-160 running temps once warm. But the audible alarm (other side of housing), never shuts up...buzzes the whole time...even when I haven't fired up...so i just unplugged it for now. Does that point to just a bad temp sender that has no resistance?

 

[04fxdwgi]

Re: Temp Sender Audible won't go off

I have read the sticky about checking the sensor wiring by grounding the wire, so I don't mean to ask a dumb question...but I'll ask anyways. I have a 5.7L Mercruiser V8. I replaced one temp sender and now my thermostat reads around 130-160 running temps once warm. But the audible alarm (other side of housing), never shuts up...buzzes the whole time...even when I haven't fired up...so i just unplugged it for now. Does that point to just a bad temp sender that has no resistance?

If you disconnected the wire and the alarm stopped, then I would say you have a bad temp switch. They are an on / off "switch", not variable resistance, unlike the "sender", which is a variable resistance for the gauge. If the switch is cold, it should indicate an "open" (very high resistance) when tested from the terminal to ground with an ohm meter. When overheated, they show a "closed" (very low resistance) on the meter when tested and allow the alarm to sound by grounding the sense circuit.

Should also mention, the same alarm sounds for low oil pressure and low drive oil reservoir level (if you have the oil bottle), also.

 

[dubs283]

Re: Temp Sender Audible won't go off

They are an on / off "switch", not variable resistance, unlike the "sender", which is a variable resistance for the gauge. If the switch is cold, it should indicate an "open" (very high resistance) when tested from the terminal to ground with an ohm meter. When overheated, they show a "closed" (very low resistance) on the meter when tested and allow the alarm to sound by grounding the sense circuit.

Should also mention, the same alarm sounds for low oil pressure and low drive oil reservoir level (if you have the oil bottle), also.

depends on the type of ignition system the o.p. has

carb'd, efi, t-bolt, hei??

there are a few different styles of overheat switch and they operate differently

 

[Don S]

Re: Temp Sender Audible won't go off

Gauge senders are not what sounds the alarms. There are alarm switches for that.

As dubs said, without knowing exactly what engine you have, it's impossible to tell you for sure what or where the problem is.

Mercruiser serial numbers are a necessity as information does not go by year.

 

[Chavez1978]

Re: Temp Sender Audible won't go off

It is engine serial OF438792. I bought the Temp Sender Unit #806490T for the side that displays actual temp on the analog gage. It started working. The other side has a non-OEM sending unit in it...which I can only tell because it doesn't have the same male connector on it (guy at OReilly's told me it should work)...it's a spade type. When I plug it in, like I said, the buzzer immediately sounds..only unplugging it causes it to stop. I tried to ground it just to test the wire, but couldn't seem to make that happen...i think it's grounding through the sensor that's in there or the alarm wouldn't sound, right?

Stops as soon as it's unplugged? When I looked at mercruiserparts.com, it is a bit confusing. It shows the 806490T (dual). Does dual indicate it's the same sensor for both sides? I appreciate the help here...

This is where I went looking for a part, but it only says I need one ofhttps://www.mercruiserparts.com/Show_pictures3.asp?dnbr=816596&ivar=IMAGES/COMMON/38504.png&inbr=1014&bnbr=90&bdesc=ELECTRICAL+COMPONENTS%28IGN%2E+MODULE+MOUNTED+ON+EXH%2E+ELBOW%29

I can't tell what I need on the right side...like i said...the 806490T seems to be allowing my temp gage to be working...the other line items on that sight say "optional". Any help is appreciated. Sorry I'm new to all of this. The right side is the audible circuit only. Also apologize this is the best photo I had...i didn't take the picture for purposes of investigating this, and the boat is stored an hour away or I'd get a better photo.

 

[Chavez1978]

Re: Temp Sender Audible won't go off

Any help is appreciated..sorry for the bump.

 

[Don S]

Re: Temp Sender Audible won't go off

The 806490T is a temp gauge sender, and is not part of the alarm system as I said before.

You need to find what looks similar to a gauge sender, but it's a switch. It will have a tan/blue striped wire going to it.

 

[Chavez1978]

Re: Temp Sender Audible won't go off

The 806490T is a temp gauge sender, and is not part of the alarm system as I said before.

You need to find what looks similar to a gauge sender, but it's a switch. It will have a tan/blue striped wire going to it.

Don, that is what I'm talking about then I suppose. It is on the opposite side of my thermostat housing. My apologies I'm new to boats. It has a tan wire going to it. When I bought the boat, both sides or the thermostat housing had what appears to be identical sensors in them, and both have an identical colored wire. One side apparently does operate the gage, the other, when plugged IN has an alarm it keeps triggering.

If I can't figure it out I'll hire a marine mechanic. I was hoping someone on here could shed some light. I've done the research I know to do.

 

[Don S]

Re: Temp Sender Audible won't go off

Tan is for the gauge sender.
Tan/Blue stripe is for the alarm switch.

Might have to untape the wires a little bit, the blue stripe may be faded and look tan.

 

[Chavez1978]

Re: Temp Sender Audible won't go off

Tan is for the gauge sender.
Tan/Blue stripe is for the alarm switch.

Might have to untape the wires a little bit, the blue stripe may be faded and look tan.

Ahh...i see. So it could very well be that the wrong thing is screwed into the thermostat housing...like i said..i've just now owned the boat a year and found some odds and ends things..i'll look around on mercruiserparts.com

 

[Don S]

Re: Temp Sender Audible won't go off

Ahh...i see. So it could very well be that the wrong thing is screwed into the thermostat housing...like i said..i've just now owned the boat a year and found some odds and ends things..i'll look around on mercruiserparts.com

Why are you looking for parts right now, shouldn't you first figure out if the problem is your temp switch? It could be oil pressure switch as well.

 

[Chavez1978]

Re: Temp Sender Audible won't go off

Don S, this is the same setup I think I have...i guess my ultimate question...is if i have a sender in one side...left side facing the engine...what exactly should i screw into the housing on the right side? I know what wires are there...just not sure what component should get screwed into the block.

http://forums.iboats.com/mercruiser...dual-temp-senders-one-temp-sender-459982.html

 

[Chavez1978]

Re: Temp Sender Audible won't go off

Why are you looking for parts right now, shouldn't you first figure out if the problem is your temp switch? It could be oil pressure switch as well.

Sorry, I already grounded the wire you're talking about and sure enough that circuit works..it trips the alarm....when it is not grounded, but unooked it doesn't sound the alarm. Then, once I hook it onto the sensor in the manifold/housing it once again goes off...it makes me think that the sensor is bad causing it to ground completely tripping the alarm....what else could i do to troubleshoot...because symptoms follow this circuit that's what I think is wrong...

 

[Don S]

Re: Temp Sender Audible won't go off

Sender in one hole, switch in the other.
switch goes in the side with the tan blue wire
sender goes in the side with the tan wire.

 

[Chavez1978]

Re: Temp Sender Audible won't go off

Sender in one hole, switch in the other.
switch goes in the side with the tan blue wire
sender goes in the side with the tan wire.

I cannot find a part number for the switch...that's what i'm asking. What switch? Mercruiserparts.com did not help me locate a switch. I'm wondering if anyone can help me with a part number!

 

[Don S]

Re: Temp Sender Audible won't go off

To troubleshoot, take the tan/blue wire off the alarm switch and see if the alarm stops. Don't let the wire end touch ground, or the alarm will sound. That's how it works.

 

[Chavez1978]

Re: Temp Sender Audible won't go off

To troubleshoot, take the tan/blue wire off the alarm switch and see if the alarm stops. Don't let the wire end touch ground, or the alarm will sound. That's how it works.

That's exactly what I did. That's why i'm assuming I have a bad switch..but I don't know what switch to buy.

 

[Don S]

Re: Temp Sender Audible won't go off

Look under Audio Warning System.

 

[Chavez1978]

Re: Temp Sender Audible won't go off

Thank you so much! Sorry this was difficult. That was exactly what I needed to know.