instrument cluster IVR

Reply #30 – July 12, 2014, 09:00:36 AM

this week update

R&R'd the alternator and battery as a matched set.

Results- no change- temp gauge still hangs out a tad higher than the actual real engine temp being shown on the radiator cap.
Having the radiator fill cap with built in temp guage from advance helps us understand the temp reading on the dash is actually too high.

Testing we did
(meter turned on set to ohms, R x 200, connecting red lead to black lead, meter reads .1 to .2 ohms.. so that's our calibration)
-measured the resistance of the red wire from the cluster connector (unplugged) going out to the temp gauge sender= 1.2ohms (both ends isolated , easy test since it a home run)
-wiggle test at the 90deg boot yielded a fluxuating resistance but not very much so........
-at the 90deg boot connector in the engine bay, we penetrated the insulation about 2'' upstream of the connector and the ohms was about .2
***I cant see 1 additional ohm being a concern unless my math is off.
-with IP cluster unplugged and ign sw unplugged, the tiny resistance (gray) wire in parallel with the large Gray / yellow reads 8.5ohms
-with a hot motor, with the 90deg red wire unplugged, the temp sender reads 78ohms to the brass housing and the lower intake. (this is the resistivity I need to get higher to simulate lower guage reading).
-with all things plugged back in, KOER, input to the ivr is approx. source voltage, the output is a pulsing 8 to 11vdc.
*****the gas guage is very correct, son ran it out of fuel (well near) and the visual display matched the end result),,, fuel gauge operates off the accuracy of the IVR output which complicates matters since the IVR also drives the temp gauge needle display.
-resistance of the temp gauge matches the resistance of the fuel gauge , both are about 12.8ohms

son says he is adding 3 and then 2 100 ohm resistors in parallel at the 90 deg slip on connector in series with the sender to calibrate and put about 33 to 50 additional ohms on the circuit. he needs to let me know how this goes.. yet I cant still seem to find the root of this problem.

guage seems fine
wiring seems fine
sender (that's the third one we've swapped in)
cant use my 20th to compare notes with since I don't have the same sender as he does

and for the life of me,, I totally forgot to double check the chassis to engine ground bonding..... its all connected from what was provided by ford,, I totally forgot to jumper cable an additional temporary ground in during our testing.

I am stumped.

sent my son the Trinom layout / link, he may end up building this and seeing if the results change. a part of me tells me there wont be because of the fuel guage isn't acting up. when the guage gets up at 80 and 90% needle swing on warm days,,, there has to be an issue.
We assumed ate first it was the TC nose swap but in body and appearance section here, we modified and added a front scoop to solve that.
additionally we even modified the bumper cover by cutting the openings of the slots along the bottom to introduce more air.

instrument cluster IVR

Reply #31 – July 20, 2014, 12:12:33 PM

How high does it read, when the car is idling and the radiator fan just turned on? My needle is in N (the top letter of the word NORM) when the fan start blowing and when it stops the needle fall down somewhere to the middle of the range.