temp gauge/operating temp question

i recently did the gauge cluster swap, 2 weeks ago maybe. i didnt have the stock bung in the rear of my new 0630 head to mount the temp sensor so i didnt get the temp gauge working until i installed the sender in the upper radiator hose about a week later. i pulled the cluster and the sender from the junk yard. its great being able to actually monitor how my jeep is running. im idling at about 500, and oil pressure is at about 30. funny thing is i never seem to reach optimum operating temp according to the gauge. the gauge never seems to get past 155. im assuming normal operating temp is about 200. i know i wont get any reading until the thermostat opens first the first time on a cold start so i must be reaching 210 right?

how accurate is the stock gauge? it has to be more accurate than this. could i have gotten a bad sender? its not possible that im running this cold is it?

'95 4.0 aw4

bump

Which hose is the sender in?

If it's after the rad/before the motor it will be alot cooler.

Every 4.0 I've ever seen/owned ran about ~210.

ive got the sensor in the upper radiator hose. do i have my coolant flowage thinking backwards?

Your in luck, I think the answer just dawned on me. Assuming you have the right gauge and sensor, that they are not mismatched, and that they are both good, not defective, then the problem is you do not have the sensor base adequitely grounded to the engine or frame. The sensor base, threads, are the return electrical path for the sensor. :doh:

IT is reading some because of the high conductivity of the coolant, but reading low because of the added resistance of the default ground path it found through the coolant. You need a solid, ground, less than 1 ohm between the brass thread base and the battery negative post.

omg, i feel like an idoit. THANKS ECOMIKE! can i just run a ground wire from the base of the sender?

tigerShark said:

omg, i feel like an idoit. THANKS ECOMIKE! can i just run a ground wire from the base of the sender?

Click to expand...

Yes, but you will need to find a way to maintain good solid electrical contact.

My sensor screws directly into the block... I should assume that this ground is sufficient, no?

Euclid said:

My sensor screws directly into the block... I should assume that this ground is sufficient, no?

Click to expand...

yep, unless your negative battery cable is broken/disconnected from the side of the block.

Drats, back to the drawing board. My aftermarket gauge never gets past 150.

Euclid said:

Drats, back to the drawing board. My aftermarket gauge never gets past 150.

Click to expand...

after market gauge or sensor? aftermarket gauge will work with an aftermarket sensor/sendor but the oem gauge may or may not work with an aftermarket sendor. it depends on how the gauge is calibrated for resistence.

Both gauge and sender are "autometer" brand.