Aftermarket Gauge Reading High

[Nick88]

Hey I have a 1988 TBI 350 Blazer with a 700r4. I installed a while ago a B&M trans temp gauge into the pressure test port to read the temp in the trans. It always read high but I figured it might just be innacurate and the trans runs a little hot. So either way finally I was sick of seeing my trans gauge in the red even though I have a monster cooler so I checked with a laser thermometer. When the gauge read 220 the pan was around 140-150 degrees, the hot lines going into the rad were around 140ish and going back to the trans after the cooler were around 100-120. This was after a short drive. I grounded the gauge good and i put a secondary ground from thr sender to the frame but it still reads too high. Any ideas??

 

[Nick88]

Anyone?

 

[RDF1]

I'd try another gauge.
The line pressure port is usually 10-15* higher than the pan temp.

 

[Nick88]

I'd try another gauge.
The line pressure port is usually 10-15* higher than the pan temp.

Yeah but this is way higher like it just read 230 after driving for 20 mins

 

[GrimsterGMC]

I have been having a lot of problems with pressure sensors lately being way out of calibration. I have been checking every gauge and sensor against a known pressure source before trusting the readings. You can do the same with your temp gauge by boiling some water and dipping the sender into it and check against a thermometer for accuracy. These days you can never take for granted that even a new item will be accurate, especially when it is critical for the longevity of your drive train.

 

[PlayingWithTBI]

^^^This - stick it in boiling water - s/b 212° F, 100° C. Stick it in ice water - s/b 32° F. 0° C These readings are +/- a couple depending on elevation

 

[Nick88]

I wilk test the boiling water, if it is off do we think its the sender?

 

[RDF1]

I have been having a lot of problems with pressure sensors lately being way out of calibration. I have been checking every gauge and sensor against a known pressure source before trusting the readings. You can do the same with your temp gauge by boiling some water and dipping the sender into it and check against a thermometer for accuracy. These days you can never take for granted that even a new item will be accurate, especially when it is critical for the longevity of your drive train.

Post-Covid everything seems to be junk..
I test every Map/Pressure sensor and Temp sensor before using them.