Author Topic: Unknown sensor found in the thermostat housing of 86 suburban. Help?  (Read 1458 times)

Offline TheBurbandtheWidow

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Just replaced my thermostat housing and was able to identify and replace one of the two sensors. Through this forum I figured out the Thermovacuum sensor but need help with the other sensor. I don't believe it is original and it is definitely broken. Any help would be awesome! I have an 86 k10 suburban with a stock 350.

Thanks

Offline VileZambonie

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Re: Unknown sensor found in the thermostat housing of 86 suburban. Help?
« Reply #1 on: March 16, 2021, 06:36:39 PM »
EFE Coolant switch,

This system uses an electrically heated grid, to heat air/fuel mixtures during cold engine operation. The grid is located under the primary throttle bore and is integral with the carburetor insulator assembly. Current flow through the heater grid is controlled by a coolant temperature sensitive switch on all except models with the C-3 system. On models with C-3, current flow through the heater grid is controlled by the C-3 system computer through the EFE relay.
On non-ECM controlled models, battery voltage is applied to the EFE temperature switch either through a relay or directly from the ignition feed circuit. When coolant temperature is below the switch calibration point, the switch is closed and current flows through the heater grid. When coolant temperature exceeds the switch calibration point, the switch opens and current flow through the grid is stopped.
On models with C-3 system control, battery voltage is applied directly to the heater grid through the EFE relay. Relay operation is controlled by the ECM based on signals from the C-3 system sensors, allowing the ECM to maintain a more constant intake charge temperature.
,                           ___ 
                         /  _ _ _\_
              ⌠ŻŻŻŻŻ'   [☼===☼]
              `()_);-;()_)--o--)_)

74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline TheBurbandtheWidow

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Re: Unknown sensor found in the thermostat housing of 86 suburban. Help?
« Reply #2 on: March 18, 2021, 06:23:12 PM »
Thanks for the info. Would you happen to know a part number or link to a replacement EFE coolant switch. I cannot find one that matches the one I have. I am also wondering if I could replace that switch and the harness connector instead of trying to find an exact match.

Offline DanMcG

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Re: Unknown sensor found in the thermostat housing of 86 suburban. Help?
« Reply #3 on: March 19, 2021, 04:14:37 AM »
First I've ever heard of an EFE heater, thanks VZ! I had to look around, and all I found are units for 2 BBL's.
https://www.carburetion.com/efe.asp

Offline VileZambonie

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Re: Unknown sensor found in the thermostat housing of 86 suburban. Help?
« Reply #4 on: March 21, 2021, 08:11:57 AM »
It's pretty rare to actually see one of these systems intact, if this is actually the correct application, original engine, emissions calibration, etc. Those heater systems usually failed or burned up, is yours still there? Is this the original engine? What's the engine code? Is the emissions label still there? You will find many of these types of parts are obsolete.
,                           ___ 
                         /  _ _ _\_
              ⌠ŻŻŻŻŻ'   [☼===☼]
              `()_);-;()_)--o--)_)

74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10