I've replaced an SSAC brand time delay relay twice because the delay time gets too short.

When new, they spec. at 0.2 - 10 seconds. I set them at about 7 or 8 seconds. After a few years of use they can't even do 3 seconds.

The timer section is solid state, but the relay is metal contacts. I'm running a sump pump so I put a capacitor across the relay contacts.

Performing autopsy, I see the relay contacts are in beautiful shape. I measure the timer pot as smoothly varying from about a dozen ohms to one megohm.

What might be causing this degradation?

 

If the timer uses an RC circuit for timing and the capacitor is an electrolytic type, it could be the reduction of the capacitor capacitance, since electrolytics are not particular stable for their capacitance value versus time.

Can you access the internal capacitor to replace it (it should be connected to one terminal of the pot)?
If so, try to replace it with a similar value ceramic or film-type capacitor (they likely will be physically larger for the same capacitance value).

 

It would take some digging. It's all potted with greenish, waxy, potting compound.

Thanks for the tip!

 

Is this Timer mounted in a particularly HOT environment ?
Heat will definitely shorten the Life-Expectancy of a Capacitor.
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Cool, damp. (Where a sump pump typically is.)

 

What make/model is it.

Can you take it apart and see what is inside.?

 

If the timer uses an RC circuit for timing and the capacitor is an electrolytic type, it could be the reduction of the capacitor capacitance, since electrolytics are not particular stable for their capacitance value versus time.

Can you access the internal capacitor to replace it (it should be connected to one terminal of the pot)?
If so, try to replace it with a similar value ceramic or film-type capacitor (they likely will be physically larger for the same capacitance value).

There's a little more to this story: There now isn't much difference in delay between low and high setting of pot. I wonder if a dead op amp is screwing up the math?

 

I wonder if a dead op amp is screwing up the math?

Op amps seldom die unless overstressed.
What makes you think there's an op amp in the circuit?

 

Op amps seldom die unless overstressed.
What makes you think there's an op amp in the circuit?

Typical timer circuits have one or more op amps. I can see the 10u electrolytic cap for timing, but there are 3 more small film caps and 7 resistors poking up from the potting. The rectifier and any IC are buried. If the big cap has actually lost 75% of its rating, replacing it might result in an adjustment range of 7 - 10 seconds, not the original 0.2 - 10 seconds. I honestly can't say if there is actually any adjustment range left. It might be a constant 2.5 seconds at any pot setting. A bad pot would explain it, but the pot tests good.

 

Post picture of it.

 

Typical timer circuits have one or more op amps.

More typical is a 555 timer chip.

 

More typical is a 555 timer chip.

Update:
The 2nd device (with most components hidden under potting) started working properly again. It has been running without the splash guard/cover over it. I have now reinstalled the splash guard. There might have been condensation inside the cover that ran down onto the relay. I suspected this before, so I poured some alcohol on it and used a blow dryer on it for a couple minutes. That didn't help. Thought about cooking in toaster oven, but since the 1st device had been dry for months and still not working, I thought I needed to look for a different cause.

Still could just be a weak connection somewhere.