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Is there any calibration adjustment on the old, 1970's vintage, Stewart Warner temperature gauges, and does anyone have the sending unit resistance values for the engine when cold and when at operating temperature?
Last season my temperature started running in the 170 F - 180 F degree range compared to 150 F - 160 F it had normally operated at. I checked the water flow and found that it was less than 1GPM at 1000 RPM. Installation of a valve in the thermostat bypass line to restrict the bypass flow got the temperature back to the 160 F - 170 F range.
This spring I decided to do some work on the cooling system which included an acid flush and mechanical scraping/rodding of the water jacket and head (first in 30 years), installation of a new jacket cover and inlet elbow, clean up and testing of the thermostat, and rebuild of the water pump including replacement of the "shoe". The shoe replacement more then doubled the water flow rate.
Apparently I did a good job, because this year I barely get the temperature gauge to register over 100 F. Just going by feel the engine temperature appears to be normal, and is certainly greater then 100 F. I checked out the temperature gauge and sending unit using Don Moyer's procedure and both units appear to be functional.
The gauge deflects slightly when power is applied, deflects to full scale when sensor wire is grounded, and the grounding is good.
The sending unit resistance is 980 ohms when the engine is stone cold and drops to 360 - 370 ohms after the engine has been cruising for 20 minutes at 1600 RPM (gauge shows 100 - 105 F). When I tap the gauge it briefly climbs to 140 - 150 F and then drops back to 100 F. About 15 minutes after stopping the engine the resistance measures at 330 ohms and the gauge indicates about 110 - 115 F.
I'm inclined to think that the gauge is bad but can't understand why it would stop functioning since it was Ok last year.
Last season my temperature started running in the 170 F - 180 F degree range compared to 150 F - 160 F it had normally operated at. I checked the water flow and found that it was less than 1GPM at 1000 RPM. Installation of a valve in the thermostat bypass line to restrict the bypass flow got the temperature back to the 160 F - 170 F range.
This spring I decided to do some work on the cooling system which included an acid flush and mechanical scraping/rodding of the water jacket and head (first in 30 years), installation of a new jacket cover and inlet elbow, clean up and testing of the thermostat, and rebuild of the water pump including replacement of the "shoe". The shoe replacement more then doubled the water flow rate.
Apparently I did a good job, because this year I barely get the temperature gauge to register over 100 F. Just going by feel the engine temperature appears to be normal, and is certainly greater then 100 F. I checked out the temperature gauge and sending unit using Don Moyer's procedure and both units appear to be functional.
The gauge deflects slightly when power is applied, deflects to full scale when sensor wire is grounded, and the grounding is good.
The sending unit resistance is 980 ohms when the engine is stone cold and drops to 360 - 370 ohms after the engine has been cruising for 20 minutes at 1600 RPM (gauge shows 100 - 105 F). When I tap the gauge it briefly climbs to 140 - 150 F and then drops back to 100 F. About 15 minutes after stopping the engine the resistance measures at 330 ohms and the gauge indicates about 110 - 115 F.
I'm inclined to think that the gauge is bad but can't understand why it would stop functioning since it was Ok last year.