Low Coolant Level Sensor and Buzzer - The Last Thread
 

After disassembling the front harness on the drivers side of my FD (LHD) I was unable to work on it again for over 2 months.

When I could get back to it I found that I had forgotten where a couple wires were supposed to go.
Had one of the connectors not broken off this would have been a no brainer, but...

So, I left these wire exposed, finished the wire re-wrap, filled the radiator, turned the power on.

10 seconds or so later the low coolant buzzer started buzzing.

Now, I was fairly sure the 2 leftover wires were those for the coolant level sensor, but I didn't want to hook them up until I was sure.

If you've ever dealt with low coolant level sensor issues, and have searched here, you will know there aren't any complete threads on the topic, so I am creating one here.

You can find most of this stuff if you search long enough, but it's kind of a pain.

So, here's what I found over the weekend, all in one spot.

1. As shown in the pic, the brown/white wire with the blue tabs is the wire that connects to the coolant level sensor, then goes to connector X12 and on to the CPU.
A shown in the pic, mine has a green extension on it from a repair.

2. The black/red wire in one of the other pics goes directly to the coolant level sensor. This one is kind of of confusing, as it does not appear in the wiring diagram. More on that in a bit.

3. The coolant level sensor is on the front of the thermostat housing. As you can see in the pic, this is a black wire. This black wire goes to the ignition harness, and is routed behind the alternator. Somewhere in the harness the black wire is connected to the black/red wire seen in a previous pic. This change does not appear in the 93 wiring diagram.

4. Grounding the brown/white wire will stop the coolant buzzer. However, when you ground this wire, the buzzer does not immediately stop. It takes 10-15 seconds of keeping the wire grounded before the buzzer stops. Likewise, when connecting the black/red wire to the brown/white wire, it takes 10-15 seconds for the buzzer to stop.

This was kind of had me confused for awhile, as I would ground the brown/white wire to make sure I had the correct wire, but the buzzing would continue. Then I noticed that when turning on the ignition key, it would take 10-15 seconds ( I never timed this) for the buzzer to start. So, I grounded the brown/white wire, and the buzzer would stop. So then I connected the black/red wire to the brown/white wire, left it there, and the buzzer eventually stopped. Success!

If your low coolant buzzer continues, and:

* You've checked the continuity of the wiring
* Grounding the brown/white wire stops the buzzer

In this case it is most likely the sensor needs replaced. I found a number of threads where folks found the sensor was simply bad.

Nice.

Updated the FAQ thread with a link to this thread.

Very helpful consolidation :nod:

good stuff.

i emphasize the part on grounding the wire for 15 seconds to stop and start the buzzing. knowing this stops alot of headache if known before hand.
many people think that the issue is somewhere else because of this. lol

nice write up. does anyone think doing this just to disable the buzzer completely would be a good idea? with someone that regularly checks servicing on their car would it really make a difference?

I wouldn't recommend doing that temporary is one thing but disabling permanantly is a no go in my books.

even if you regularly check you car...things can still happen while driving.

dont disable! just stop the buzzing to wait for new parts to come in

This is a great write up , I've been going crazy finding out why the buzzer wouldn't shut up and just now noticed I have the brown /black wire , disconnected from the red black . now I gotta find it haha

what about second gen?
 

Great writeup but do you happen to have this info for a second gen....'88? I am sure its not the same configuration but I just got the coolant buzzer for first time.

Thanks

Terri

No, I do not have that info.

Ok thanks

Terri

So bringing back an old thread to life.

I have the coolant buzzer issue on my car, searched and read just about every single "Coolant Buzzer" thread available in the world. All say ground the wire out to shut up the buzzer, or there is a bad sensor, or bad wire.

I started my troubleshooting and found a few things wrong, Continuity from the "Black" wire that goes from the water pump sensor to the "Brown/White" wire was not real good. So I repaired both ends of the wire with new connectors, tested continuity, perfect.

Moved on to the "Brown/White" wire, found that the wire at the connector was broken. So I got a new connector, spliced the wire, soldered it to the new connector, tested continuity, and resistance (check in at 0 Ohms indicating a good solder).plugged the wire back in, buzzer lives on...

Now I search around and I find my Oil level sensor is also needing repair, I follow basically the same procedure above. repair connectors, solder wire, test to make sure its a good solder, plug it back in, buzzer lives on.

So lets move on to the "add coolant" portion of the troubleshooting, because that's in all of the threads I find. I get my Lisle funnel, start the car, and let the car get rid of all air bubbles in the system. this goes on for about 90 minutes, just to be sure. checked all coolant levels and buzzer lives on....

At this stage of the game it can only be the sensor right? even though its a brand new water pump assembly in the car with a new sensor, I buy a new sensor anyway. put in the new sensor.... and wait for it... buzzer lives on!!!

So I say screw it, i'm grounding this wire and moving on with my build because I just cant stand that damn thing buzzing all day... so I grab the wire, ground it and.... buzzer lives on!! WTF??!? I ground both the oil level sensor and the coolant level sensor and nothing, buzzing continues without any sign of stopping, and yes I waited the required 20 seconds, heck I grounded it and waited 10 minutes with no change.....
Now I bust out my workshop manual, find the wiring diagram and see where this stupid thing goes into so I can verify that its not broken somewhere. From my understanding, it actually goes into the X-18 harness, behind the instrument cluster. so I pull the cluster and everything is plugged in correctly.

Now i'm stuck, no grounding works all the wiring is repaired and checks out fine, but my buzzer doesn't shut up... the only time I got it to shut up was when I had the cluster out and I left the plug that goes into the cluster that feeds the temp gauge out, when I did that no buzzer, but that more than likely is because the circuit was not complete.... Anyone have any ideas? i'm about to go nuts with this buzzer....

Is there continuity from the black/red wire (#3 in original post) to the sensor?

Did you check continuity between where it’s at on the x-18 harness and in the engine bay to see if the wiring is good throughout the car and engine bay?

what about grounding it straight out of the x-18 plug?

I was thinking of doing this exact thing. though I have been trying to figure out how I'm going to accomplish that feat... my multi meter leads aren't that long...might have to make an extension out of speaker wire that should work. I'm also going to replace the CPU #2, I have a spare here anyway just to see if it makes a difference.

I made an extension for my meter out of wire when I was trying to track down the same type of thing. Worked perfect for it.

Just out out of curiosity, you verified the right connector in the engine bay? I ask because I had a similar issue the other day. I couldn’t get mine to turn off for anything. I was pretty close to stabbing the speaker out under the dash because it was annoying me. I found this thread and started looking for more connectors. Turns out the reason mine was doing it was because I was using the power steering connector. I have P/S and AC in the car still so everything is a tight fit. I found the right connector in the bottom of the engine loom under the ac compressor. There was like 1/2” of wire and the connector coming out of the harness and it was on the bottom of the harness so I couldn’t see it. I just felt around until I got lucky.

replacing th cpu would be the next resort though if you have good continuity from the connector inside to the connector in the engine bay.

Is your low low coolant light on as well?

So I ID'ed the wires coming from the sensor (black with red dots) that go behind the power steering pump so I know that one is the correct one for sure. From all my searching the coolant level sensor wire in the harness is a Brown/White wire which is where the wire from the sensor is plugged into, power steering is Black/Red, Oil level sensor is Blue/Red.

There must be a break in the wire between the engine bay and the dash, or I have a bad CPU #2...

FYI, the low coolant light is NOT on when the buzzer is going off, so perhaps the cluster is at fault... Unless there is something else that makes that stupid buzzer go off that I am not aware of.

Burped it and buzzer went away!
 

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We burped the radiator line and the buzzer stopped thankfully!
We

There is definitely no air in my system, as that was part of the troubleshooting process.

Won't hurt to bump anyway
 

bUMP

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We didn't think there was any air in it either but apparently there was. Might not hurt to bump it anyway.

I have, multiple times... also grounding the wire out didn't work as it should, which means, even if the sensor was working, the buzzer probably would continue either way since the connection back to the system isn't complete somewhere.

Anyone know if the "exhaust heat" light triggers the buzzer too? Haven't been able to track that down yet...

Mine didn’t trigger the buzzer.

have you had a chance to check continuity between the harness side and the plug in the engine?

I have been bogged down with a few other projects and haven't had a chance to keep tracing this thing down. I pulled the middle plug from the CPU #2 so that shuts the buzzer off, but it also takes away all my interior lighting, power mirrors, etc. kind of a pain so I should be getting back to it this week.

I however am starting to think its not the coolant buzzer, as the coolant light never comes on. it is 100% burped and the coolant is full. If I am not mistaken, the oil level sensor, also triggers the buzzer, might be the only two things that trigger it if I remember it correctly.

Probably will buy a new one and replace it on my first oil change, just crossed the 300 mile mark on my brand new engine so breaking it in before the warranty from Mazda runs out. anyway, i'll update the thread once I have this buzzer figured out.