
Quick overview
- One on and one off The set contains a single on tripper and a single off tripper, the pair that defines one run window.
- Fits all T100 Series Works with every T100 Series time switch and mechanism Intermatic builds.
- Sets the schedule The trippers clamp to the dial and are what actually throws the switch at the times you choose.
- Add a second cycle Fit another set if you want the timer to start and stop twice in the same day.
- Replaces broken ones Trippers get brittle, lose their grip on the dial or snap off, and the timer then runs continuously or not at all.
- Genuine Intermatic Part number 156T1978A, made to seat properly in the T100 dial.
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Product details
The Intermatic 156T1978A tripper set contains one on tripper and one off tripper for T100 Series time switches and mechanisms.
What the trippers do
A mechanical time clock is just a motor turning a dial. The trippers are the small clamps you slide around that dial, and they are what physically throws the switch as the dial rotates past them. The on tripper starts the load, the off tripper stops it. Move them and you move the schedule.
Why they get replaced
Trippers live outdoors in a timer enclosure for years. They go brittle, the clamping screw strips, or a tab breaks off. When that happens the timer looks fine and the motor still turns, but the pump either never starts or never stops.
Running more than one cycle
One set gives one on and off cycle per day. If you want the pump to run in the morning and again in the evening, fit a second set of trippers for the second window.
| Brand | Intermatic |
|---|---|
| Manufacturer part number | 156T1978A |
| UPC | 078275002135 |
| Type | On/off tripper set |
| Included | 1 on tripper and 1 off tripper |
| Fits | All T100 Series time switches and mechanisms |
| Shipping weight | 0.05 lb |
| Ships | Parcel |
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