Capacitor on back of instrument cluster

[montanasynchro]

Hi,

I have a 87 Syncro, analog clock and no tach. I pulled the instrument cluster and found this capacitor. I plan to use a new wiring harness to replace the blue film. I believe this capacitor has something to to with the coolant temp gauge. If so, I am not sure of its use.

Any ideas on how to use the new wiring harness hook up ? I would think I would need to jump this capacitor as when the blue film is removed, it will be by its lonesome.

Any thoughts would be appreciated ( especially if you know what you are talking about)

thank you for your help

[0to60in6min]

isn't a '87 supposed to have tach and digital clock? or was it replaced by a '85 instrument cluster?

[montanasynchro]

I don't know what most 87s have, but our family is original owners so no mods. Even if they put in a earlier cluster when made, I can't find a capacitor at this location on earlier models looking at the diagrams.

[tencentlife]

Tracing the connections right there on your circuit foil would tell you what it does.
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[RawUmber]

I don't know about the new wiring harness, but I'd hope it would include everything you need to replace the old one. Seems strange to need to re-engineer it.

[kiltedhiker]

Base models had an analog clock and no tach.

[kiltedhiker]

Base models had an analog clock and no tach.

[dabaron]

a capacitor stores energy, it possibly could power the clock after the battery is disconnected to maintain the current time.
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[fxr]

[dabaron]

[tencentlife]

Once again: Trace where it connects and you know what it does. It's that simple.

There are no caps in the cluster diagrams so this is a unicorn, but that doesn't matter, just look at the traces and it's purpose will be obvious.

Most likely it's connected between the fuel level sender input and ground, in order to dampen the float movements. But a thermal gauge is slow to respond so the damping was unnecessary and it went away., That means it won't be needed in the new circuitry, either, so it can be ignored.

If it had another purpose, whatever it is it wasn't continued, so in all likelihood it can still be ignored, but simply tracing it's connections will tell.

If the OP just posted a little wider pic anyone could see the traces and answer the question.
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[crazyvwvanman]

Both tach and analog clock clusters got the capacitor.
In my experience, STARTING mid 87 model year.

Mark

[crazyvwvanman]

Ok, the - end of the capacitor connects to the cluster ground.
The + end connects to the temp gauge sender signal wire which is also the coolant low level warning signal wire (hint hint).

[fxr]

[crazyvwvanman]

No, the coolant level warning relay takes care of that delay. The tank sensor feeds the relay and then the relay determines if the coolant has been sensed low for long enough to notify the driver by flashing the temp gauge led.

The coolant level relay latches the "warning" condition so the led will then continue to blink until the key is cycled off-on to reset the relay.

(tall case early type coolant level relay behaves differently, 83-85)

Mark

[dabaron]

[crazyvwvanman]

The fact that your led blinks at startup, then stops for a few seconds, and then starting blinking again points to the coolant level relay deciding that the coolant is sensed low.

Since your symptoms point elsewhere I won't go into my theory of a cause of your particular problem in this thread about the blue foil. But what happens in the cold if you simply turn on the key and watch the led for a while without starting the engine?

Mark

[dabaron]

[tencentlife]

[crazyvwvanman]

The OP photo shows a late model analog clock cluster which he says is on an 87 Syncro. I have late versions of both tach and clock clusters in hand and checked the capacitor connections on each before I posted above. Both are connected to the same locations though the trace layout of the foils obviously differs. The tach clusters have both gauges mounted below the tach instrument. The clock clusters have 1 gauge above and 1 gauge below the clock instrument.

The late 85+ versions of the coolant low level warning relay have time delays built in. They need to sense coolant low for several continuous seconds before they "latch" that condition and output a signal to the temp gauge that causes the gauge led to begin blinking. The foil capacitor in question is connected to the output signal of the coolant low level warning relay. The relay doesn't output a signal until after it has latched and doesn't latch until after a delay timer has timed out. Such is my understanding.

Mark