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Idiot light control module

O

outobie

Regular Contributor
hello all I’m working on the electrics of my 30 year old Tiara.

i have a series of warning lights on the dash that are not hooked up. Behind the dash are these two red circuit boards that seem to control the warning lights. I’ve traced some of the wires from the circuit board and am trying to figure out two things

1 does my warning light module work
2 how do I wire it.

I ll post a pic in a minute but here is background info

boat is a 1987 Tiara that originally came with twin Chevy small block 350 engines with alpha 1 drives rated at 260 HP.

the boat was repowered in 2001 with twin Chevy small Block 350s rated at 250 HP with 2bbl carbs and alpha one gen 2 drives

i believe that when the motors were swapped is when the lights were disconnected.

I dont know if they they were disconnected for a reason or if the mechanic just didn’t bother.

I’m hoping to be able to get my warning lights working properly again

can someone tell me how to test the control module to see if it works? For each warning light there are two wires on the control module.

One wire going to the (what I believe is) signal wire on the back of the respective gauge. And one wire to the warning light.

the module has 4 of these wire pairs two wires each for:

water temp
oil pressure
battery
fuel tank

there is also one additional wire on the control module.
the lone wire has been cut so I cannot confirm where it was connected. It’s a grey wire spliced into a black wire. The splicing matches the rest of the factory wiring so I’m assuming the black wire it’s soliced into is from the original tiara harness.

My my best guess is that the black oem harness wires are battery negative.

on the warning lights there are two wires, one from each warning light that goes to corresponding pair on the control module and one that is daisy chained together for all the warning lights to a purple wire. I’m assuming the purple wire is main harness OEM SWITCHED battery positive.

id like to test the module off the boat .

can anyone confirm I’d the cut wire from the module with the black wire should be to battery negative?

Can anyone tell me how to replicate / trigger the signal wire connected to the gauge? Should a full ground from the signal wire activate the warning light?
 
warning light module.jpg

from left to right, the wiring terminal pairs are as follows:

pair 1: oil gauge, oil warning light

pair 2: battery gauge, battery warning light

pair 3: fuel gauge, fuel warning light

pair 4: temperature gauge, temperature warning light

last solo terminal: ?...maybe battery negative?

the far right terminal was the cut wire that I'm speculating went to a black battery negative wire on the boat's main harness / buss bar.

one other detail...the gauges are VDO analogue gauges which are original to the boat from 1987. Each has 3 wires: positive, negative and signal.

another strange thing done when the motors were swapped is that the warning buzzers mounted to the dash were not connected...in stead, there were two little buzzers added and mounted with zip ties under the dash, (one for each engine). I tested the dash mounted buzzers and they seem to work just fine when I jump power to them. I"m not sure if this is related or not but thought I'd mention it.

thanks for any help
 
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What you are taking on my not be worth the effort - a lot will depend upon how you use the boat. I've found that lights are nice but, unless you are staring at the dash, a horn/buzzer does a much better job of getting your attention.

What you have appears to be similar to what we had (and removed) from a similar hull from that time frame. In essense, it was a bunch of compartors that monitors the sender leads and turned on the appropriate light when the sender indicated an 'error' state (too low oil pressure, too high temp,etc). depending on the logic used on the board, it may require a +12VDC connection, a -12VDC connection, or both. your terminal in question is likely the GND as the board could draw current from the 'alternator' input terminal.

you can emulate the sender functions with variable resistors or a few different fixed value resistors. for a normal single station gauge, using the prevailing american standard, 110 ohms will get you a midpoint value on the gauge, 33 ohms or less should get you full scale, and 240 ohms should get you the lowest indicated value. The only oddball is the 'battery gauge' which is usually a voltmeter - a variable output power supply is likely to be the best emulator there.

You may want to try the factory tech support department....they may be able to tell you who made the card you have and or provide other documentation....never hurts to ask...
 
The way that senders work is by variable resistance. Usually this is on the ground side of the circuit. That is, if the lamp is doing the "work" then the negative side of the circuit (the sender) is doing the resisting. So going by that logic, the way to bench test this is to supply pos 12-14V and ground the other terminal to see if the lamps light.As mark says, these lamps must light up at a certain resistance set-point baked into the board.
As to the gauges, the three wires are for the illumination and the sender, respectively.
No clue what the orphan terminal is for. If the warning lights function without it being connected then you can certainly ignore it.
Seeing that it is potted in epoxy pretty good, I'll bet it works just fine.
Remember: use adhesive lined shrink crimp terminals whenever possible. NO SOLDER ON THE TERMINALS.
Order from genuinedealz.com
 
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makomark said:
What you are taking on my not be worth the effort - a lot will depend upon how you use the boat. I've found that lights are nice but, unless you are staring at the dash, a horn/buzzer does a much better job of getting your attention.

...
Click to expand...


Last St summer my alarm buzzer went off

I had no idea what it was for since there are two motors with 3 functions each hat sound the same alarm.

with the lights hooked up I’ll be able to identify what function the alarm is for.

thanks for the info below. That’s a big help I’ll begin testing and let you know what happens
 
o2batsea said:
The way that senders work is by variable resistance. Usually this is on the ground side of the circuit. That is, if the lamp is doing the "work" then the negative side of the circuit (the sender) is doing the resisting. So going by that logic, the way to bench test this is to supply pos 12-14V and ground the other terminal to see if the lamps light.As mark says, these lamps must light up at a certain resistance set-point baked into the board.
As to the gauges, the three wires are for the illumination and the sender, respectively.
No clue what the orphan terminal is for. If the warning lights function without it being connected then you can certainly ignore it.
Seeing that it is potted in epoxy pretty good, I'll bet it works just fine.
Remember: use adhesive lined shrink crimp terminals whenever possible. NO SOLDER ON THE TERMINALS.
Order from genuinedealz.com
Click to expand...

positive seems to be supplied directly to each warning light through the purple wire and I’m assuming ground is controlled through the module somehow.

so far I’ve been unsuccessful in getting the warning light to work using the module (it works just fine without the module in the circuit)

so so far I’ve tried hooking up the mystery black lead to ground

one light lead to battery + and the other back to the module (like it was hooked up in the dash.

my assumption was that supplying battery - to the module lead that normally goes to the gauge would mimic the overheat signal from the temp gauge and cause the light to activate. This experiment did not work.

peehaps like mentioned above, the module requires a secondary battery positive signal from the battery voltage gauge lead .

i know when testing my temp gauge I can peg the the gauge full hot by grounding the sender on the top of the thermostat housing .

i had thought grounding the gauge lead would produce a similar result
 
Turns out that is an optional Crusader Engines warning lamp module. It was an option on fuel injected engines.
 
kimcrwbr1 said:
Sounds like a whole lot of too complicated? Get a box set of new guages and replace the senders then just wire it like normal IMO!
Click to expand...


I dont understand this post.

how does replacing the gauges and senders fix my warning lights?

if the warning light system is available to purchase new. I’d love a link to where it can be purchased
 
Thanks for the crusader reference... I now have something to search for .

i don’t suppose you have a link to any info on them do you?
 
I think that when the repower was done, these modules were simply leftovers from the previous engines. I don't think you need to worry about making them work.Ditto the old buzzers (unless you want to switch over the wires). Just keep an eye on your gauges, FFS. That's why they're there!
 
outobie said:
Thanks for the crusader reference... I now have something to search for .

i don’t suppose you have a link to any info on them do you?
Click to expand...

I googled "Crusader warning module" after looking up what engines originally came with the Tiara. All I found was an installation manual that makes mention of this thing and references some part numbers that also lead nowhere when googled.
 
In normal twin engine installations, the horn is separate for each engine.....in the older (pre-ECU) vintage, the horn is activated by low oil pressure, coolant too high, or gear oil overheat.....the first two usually have a gauge.....so determining the source is usually straight-forward.

If the 'module' is from Crusader, you may want to check with their tech support department....but, without a part number, your chances are not real good....another option is a crusader dealer thats been around a while....

honestly, I doubt that whoever made it is still around as the computer has taken over most engines....so finding any useful data is gonna be tough....
 
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I think ive made some progress with the info above.

the key was adding battery + from the voltage gauge.

with voltage gauge lead connected to battery + and the mystery black lead connected to battery -, and the temp gauge signal grounded to battery - it made the temp light up flashing on and off. Which is presumably what it should do in an overheat situation. Next time a warning alarm goes off I should be able to pinpoint where it’s coming from with the lights.

now I just need to find a good source for 5/16 OD incandescent indicator lights.
 
Final answer ... the modules are working perfectly now
the one last mystery wire was in fact a ground wire.

never did figure out who
makes the modules but they are now working perfectly.

they even have some reostat dials to fine tune the reading at which the warning light is triggered... I set the oil pressure light to trigger below 10 PSI

does this seem correct?
 
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