1994 Mercury 200-HP Continuous Single-tone Aural Alert BEEEEEEEEP

[pLee]

Hi folks. I need some help diagnosing [the cause of] an alarm in a 1989 Outrage 20 with a 1994 Mercury 200-HP xRI. The engine is cold. I turn the key to ON. I get continuous single tone alarm--BEEEEEEEEEEEEEP.

Normally this is a temperature overheating alarm, but the engine is cold. The engine will start up, but with the alarm, I've only run it for 10 seconds (just to confirm it would start).

The rest of the story is that I've recently replaced the built-in fuel tank. So, I removed the console and disconnected all the wiring, and recently put it all back together. When I turn it to ON, all the gauges react fine -

I read somewhere that the alarm could be from low battery voltage. My batteries--both deep cycle--are a bit old, but they show 10-Volts, the same as my car batteries which are not old.

I found an old post from Jim about the temperature sensor - http://continuouswave.com/ubb/Forum3/HTML/017301.html I'll check that this weekend.

What else should I check?

[Phil T]

Phil -

Given that you recently de-rigged the console, I would proffer the continual aural alert (for you Jim H) is most likely due to a faulty wire connection.

If me, I would cram my torso into the console and disconnect and reconnect any and all bullet connectors related to the key switch and harness. I would keep checking every one in the console and then, if no success, lift the engine cowl and continue.

[jimh]

Check the alarm module itself. Problems with alarms on those older Mercury engines are common.

[pLee]

Thanks for the pointers. I'll take a look this weekend. I'm pretty well versed at the 'stuffing the torso' part. This makes the second time I've rewired the console. The first time was debugging the rat nest of wires trying to figure out various components quit working...

[pLee]

Jim, how do I test the alarm module? I bought a Seloc manual yesterday, but it doesn't provide any details that I can find about testing the module or the alarm. It only really says what the alarms mean - overheating and oil.

However, I did find an article that described troubleshooting for the single-tone aural alarm - the steps sounded just like my engine/situation. I have two tan-and-blue wires that terminate at a block on the starboard side of the engine. When I disconnect the one that's clearly a temp sensor (from the starboard engine block, the alarm continues. When I disconnect the other (from down under other components where I can't trace it's origin), no alarm.

The catch being that I'm not sure where that other tan/blue wire goes. I see other tan/blue wires emerging from under components that go to "twin" black boxes on the very top of the motor (toward the port side of the powerhead). I'm not certain that either is the alarm control module, as my manual shows the control module on the port side of the engine over by the throttle arm - and I have a black box there just as it shows.

[jimh]

Http://Continuouswave.com/whaler/refere ... ction.html

Read above linked article.

A good test of the alarm module is to disconnect the sensors and see if the alarm still sounds. This assumes the normal circuit of every sensor is an open circuit. Without knowing exactly how the alarm module works, it is impossible to say what should be done to test it. I believe there are some procedures recommended in the article linked above.

In any alarm system there are several possible causes for an alarm:

--a real alarm

--a false alarm due to a faulty sensor

--a false alarm due to a faulty alarm controller

--a false alarm due to a faulty alarm sounder

If you plan to perform your own service and repairs on an outboard engine, the best documentation usually are the original manufacturer's literature, manuals, and service bulletins. Aftermarket manuals tend to be filled with generic advice (called boiler plate because large sections of the manuals can be "unbolted" from on manual and "bolted" into another without re-writing them).

[pLee]

Thanks for the reference. It's valuable material. Though I didn't state it, I had read it before.

My alarm module is more/less the same as item #10 in the diagram. Only differences are that mine's on top of the engine, and the brown wire in the diagram to the temp sensor - mine is brown with a blue stripe. Since my earlier post, I've confirmed that it is the wire that goes down behind the components and emerges at the block on the starboard side - joining the other wire that comes from the heat sensor on the powerhead. It is the same lead that stops the alarm when I remove it from the block. So, I'm really feeling like that's the culprit.

The only thing that makes me question that conclusion is that when I remove that tan/blue lead, I don't get any alarm when I turn the key to ON. I expected the typical "beep beep" since I didn't detach any of the other leads (like from the oil sensors). Is that an incorrect expectation?

Does the diagnosis seem reasonable?

[jimh]

pLEE--I can't offer any first-hand advice on the alarm module characteristics when the brown-blue sensor lead is disconnected. I would expect that if the aural alert is silenced when that circuit is disconnected from its sensor, then the sensor has malfunctioned.

If the sensor is a temperature sensor, they are usually very simple in their operation. A temperature sensor is generally just a switch that is operated by temperature, and most likely has an open circuit until the temperature rises above the threshold of the switch, at which point the switch closes and there is a closed circuit.

I suggest you check the resistance of the temperature sensor when the engine is cold. I would expect it to be an open circuit. If it is a closed circuit, I would infer the sensor has malfunctioned.

My impression of the alarm circuitry on these older Mercury engines is they are prone to failures. This is an aggravating situation. One would hope that an alarm system was very robust so that it never gave false alarms. One would also hope that an alarm system lacking any sort of visual annunciator of which sensor was alarming would also give clear aural cadences to identify the alarm. On these older and rather not-very-sophisticated outboard engines--these designs go back to the 1970's--I guess you will have to scratch around for the true cause of the aural alert sounding off.

Problems of this sort are often mentioned. Although it has been the goal of the website and my goal as its publisher to collect and organize information, I am afraid I cannot recall any clear and cogent information being offered on this topic. The subject of Mercury alarm modules seems to be a black art (quite appropriately for Mercury engines).

[pLee]

John - thanks as always for the continued advice. You're absolutely right - these are frustrating problems...

I should have posted again mid-last week. I had read in my manual about testing the heat sensor. It tests fine - no continuity when cold, only when hot. I also confirmed this by disconnecting the tan/blue lead going to the alarm module off the terminal block - no aural alarm. Disconnecting that lead left only the tan/blue lead from the horn/alarm and the heat sensor. The wiring diagram in my manual shows that the ignition goes into the horn/alarm, then out (neg) through the tan/blue lead to the terminal block on the engine (so that lead has power). However, since the heat sensor was cold/open, no aural alarm. Makes sense.

Leaving the lead to the alarm module disconnected at the terminal block, I tested the volts from the terminal block to the disconnected alarm module lead - 12.0 volts. That seems wrong. Rather, if module was good, I would have expected 0.0 volts since it should not be grounded through another sensor or another ground.

Also, while leaving the lead to the alarm module disconnected at the terminal block, I checked continuity from the disconnected lead to the ground wire on the alarm module (where the wire connects to the powerhead). I got two numbers to flash, then the display went to '1' (on my multimeter that mean no continuity). This makes sense to me as the oil sensor test pattern - it would have rendered two beeps had the alarm module been connected (and not giving the overheat aural alarm).

Looking back at Phil T's response, is there another wire that could be shorting out (grounding) "downstream" of the alarm module - incorrectly making the module look like the problem? Unfortunately, the alarm module is a 'black box' - literally and figuratively. Meaning that I can't 'see' into it to understand it's internal wiring.

Does this make sense?

Thanks.
Phil

[jimh]

pLEE--if you have a manual with a wiring diagram, please post the wiring diagram. I cannot follow your narrative of the circuitry very well.

[pLee]

I thought it might be tough to follow. I've attached a scan of the diagram. [I substituted a cleaner version of the diagram. I edited your description to include notations of the callout designators of the circuit components--jimh]

My engine is just like this.

The purple wire carries [current] out of the ignition switch [e] into the warning horn [d]. Then, the tan/blue wire carries the [circuit] to the terminal block at [c]. The [circuit] could be grounded by the temp sensor [a] to make warning horn [d] sound. That's not my case since the powerhead is cold and the sensor works.

From the terminal block [c], the tan/blue wire goes to the alarm module [b]. It's getting grounded there when it should not. There is plenty of oil in the reservoir and the aural alert is not the BEEP BEEP BEEP cadence.

Also, I've not touched any of those wires in my fuel tank replacement. A short could still exist, but I don't see any other wires going to the alarm horn in the diagram or on the boat.

[pLee]

Closing the loop here. My diagnosis was correct - the alarm module was bad. I took it to my mechanic with my learning/evidence and he agreed. The replacement was $500 ($350 for the part - parts on old motors are expensive). Runs great now!

[jimh]

Thanks for the follow up. I found a much cleaner drawing of the circuitry and attached it to your original post. Also see my new article that explains the circuit in detail. See

Mercury Warning Horn or Aural Alert Sounder BEEP-BEEP-BEEP or BEEEEEEEEEP
viewtopic.php?f=6&t=2139&p=12436#p12436

[jimh]

An alternative solution:

--discard the ALARM MODULE entirely. It really serves only a very limited purpose: to make a contact closure into an alternating contact closure. To pay $500 for that function seems a bit excessive;

--investigate the wiring of the float switch to determine if the alarm state is signalled by an open circuit or a closed circuit. If the alarm state is signaled by a closed circuit, you can just wire the float switch in parallel with the temperature switch. When either closes the sounder will alert you with a BEEEEEEEP. If the alarm condition is signaled by an open circuit, wire a relay coil in series with the float switch; wire the relay contacts so they close when the relay drops out. The relay coil current drain should be easily handled by the battery and charging current. This solution will cost about $4 in parts and a few minutes of rewiring.