Pyrometer Exhaust Temperature Gauge Installation Instructions

piller3gauge_large.jpgManufactured in the USA

1 year warranty


Excessive exhaust temperature can be the greatest damaging factor to the life of an engine and turbocharger. Exhaust temperature should never exceed the engine manufacturer’s specifications.

The most reliable indicator for control of exhaust temperature is a pyrometer.



• Restricted air supply
• High temperature of intake air or boost
• Altitude
• Fuel variations and contamination
• Turbocharger malfunction
• Exhaust back pressure
• Engine timing and fuel system
• Engine overloading, i.e. operator misuse, misapplication

• Excessive smoking
• Fuel waste
• Carbon build-up
• Lube oil dilution by fuel oil
• Burned valves
• Sticking pistons and rings
• Head gasket failure
• Turbocharger damage
• Exhaust manifold cranking
• Injector failure
Select image below to see large illustration! 
pyrometer_2_hewett_th.jpg  therocouple_lead_th.jpg

Installation Features:

NOTE: Hewitt pyrometers require no power. NEVER apply vehicle voltage to pyrometer terminals, damage beyond repair will occur. Only the illuminating lamp requires voltage.

Instrument Installation: The pyrometer instrument should be mounted securely to minimize vibration; flexible brackets are not advised. Locate in best viewing position. If lamp is removed during installation, lamp hole should be plugged or taped over to prevent dirt or metal particles from contaminating the movement.

Thermocouple Installation: Various threaded mounting adapters are available, i.e.1/8 NPT, 1/4 NPT, 3/8 NPT, and 1/2 NPT. If not specified, 1/4 NPT will be supplied.

Location will vary depending on application and engine. On turbo charged engines, whenever possible, thermocouple should be installed in manifold before the turbocharger - this will give the highest temperature indication and the best response time. Hewitt thermocouples are designed to tolerate this location safely and carry a lifetime warranty. If mounting pre-turbo is not possible, a lower temperature of 150-200F will result when mounting after the turbo.

For non-turbo engines, thermocouple may be installed in the manifold before or just after the exhaust pipe flange, as is convenient.

Connecting terminals have staggered lengths to insure correct polarity, plus color match to extension wire. A plastic heat shrinkable tube is supplied with the thermocouple and should be slid over the terminals after connection is made with the extension wire and shrunk in place with heat for insulation purpose.

Extension Wire: Standard available lengths are 7 ft. minimum, 12 ft., and 14 ft. maximum. If longer length is required, 2-conductor 18 gauge wire may be added between extension wire and instrument, also available color coded from Hewitt. When installing the extension wire, care should be taken to stay clear of exhaust system and chafing areas. Secure with tie wraps, etc. to eliminate wire movement. Terminal connections to pyrometer are designed to insure correct polarity.


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In addition to Exhaust temperature gauges for Chevrolet, GMC, Dodge and Fords we also offer free technical support to assist you in solving your automotive problems as well as a large list of the following products to improve your vehicles performance, economy and apperance.