Temp gauge pegged right. Not at zero but the other way.

[maluminse]

I assume this means its a bad sending unit.

Was working fine. Did some work on the car and unplugged the wires. Put it back together.

It went kind of crazy back and forth. Also worked fine for a bit. Now its pegged right. Doesnt move at all now.

Oddly when I turn off the car but the ignition is still on it drops slowly.

Wires are plugged properly. Wires look clean and well attached. Also car is not hot at all. Pegs right at start.

Thanks.

[rridge]

Disconnect the overtemp switch. Just pull off the connector from the tab on the top of the sender. The switch overrides normal gauge function. The overtemp switch is not needed for normal gauge function and was not used on the 131/Brava. Removing it after 40 yrs in the head and replacing it with an aftermarket piece which may or may not fit is a hassle you don't need.

[maluminse]

Disconnect the overtemp switch. Just pull off the connector from the tab on the top of the sender. The switch overrides normal gauge function. The overtemp switch is not needed for normal gauge function and was not used on the 131/Brava. Removing it after 40 yrs in the head and replacing it with an aftermarket piece which may or may not fit is a hassle you don't need.

Thanks. Ill give it a try.

[maluminse]

Disconnect the overtemp switch. Just pull off the connector from the tab on the top of the sender. The switch overrides normal gauge function. The overtemp switch is not needed for normal gauge function and was not used on the 131/Brava. Removing it after 40 yrs in the head and replacing it with an aftermarket piece which may or may not fit is a hassle you don't need.

Disconnected and tucked into its grommet and then black taped.

Temp gauge no longer pegged. But now it just sits. Ran car. Fan came on after 10 minutes or so. But gauge was still sitting.

What are the odds both the overtemp and gauge sending unit went at the same time?

Sending unit right?

[rridge]

It's more likely that the wires to the two temp senders have been swapped. This brief video might be useful.
https://www.youtube.com/watch?v=8DtcIlkt4BY

[jlw35]

I accidentally reversed the wires on the back of the gauge, caused the identical issue that you have. Try swapping the wires and see what happens.
Jeff

[maluminse]

Initially it was near impossible to swap them as the one closer to the firewall was bound so that it was too short to reach the further one.

I convinced myself I might have switched them and pulled the shorter one a 1/4 inch to reach the further unit.

Same result.

I tried reversing several times. If the back one was connected it pegged full. If only the front one was connected it sat and didnt respond at all. Currently there is no response at all.

Ive unplugged the overheat wire and its not connected.

Only the one near the radiator is plugged and it doesnt respond to the ignition being turned on or at all.

Bad sending unit right?

I did see it, when it was working, flip out. Like pegged then zero then pegged.

I recently replaced the head gasket. Maybe air or something else caused it to fail?

[Odoyle]

Are the temp gauge units in the correct position on the head? Most always on DOHC engines the temp gauge sender has red plastic cap and is located in the rear (firewall side) of head which gives the current reading of the coolant temp. The second temp sender has black plastic cap and is located in the front (between spark plug 1 & 2) of head and pegs the gauge right if the temp starts to go past 230°F approx. Try disconnecting the green/black wire that goes to the black sensor and see if the needle moves, it should not change the reading on the sensor. This can give you an idea if the sensor is faulty or operational.

[maluminse]

Are the temp gauge units in the correct position on the head? Most always on DOHC engines the temp gauge sender has red plastic cap and is located in the rear (firewall side) of head which gives the current reading of the coolant temp. The second temp sender has black plastic cap and is located in the front (between spark plug 1 & 2) of head and pegs the gauge right if the temp starts to go past 230°F approx. Try disconnecting the green/black wire that goes to the black sensor and see if the needle moves, it should not change the reading on the sensor. This can give you an idea if the sensor is faulty or operational.

Theyve never been removed as long as Ive had the car. Gauge has worked fine for 4 months. After the head installation it jumped around worked fine, then read overheating but not pegged and not accurate as I had just started the car. Then it went wacky, pegged to zero to pegged. Then nothing.

I plugged each wire (one at a time) into the overheat sensor and it pegged. I plugged both wires into the gauge sensor (one at a time) and nothing happens at all.

[RRoller123]

Just a long shot, but when the head was removed, were the sensors possibly installed with some sealant? They require a good ground connection.

[maluminse]

The sensors were never removed. I just replaced the head gasket.

Worked fine for about a day afterward. Then went crazy.

Seems like both sensors went bad. I mustve shorted them somehow.

My relay block looks a little wonky. But I dont think they run off relays. Looks like a direct line to the gauges but Im just guessing.

[maluminse]

Duplicate post removed.

[NSFIAT]

Mine wasn’t pegging to the right, but it had become unreliable. I know the engine wasn’t overheating and knew there wasn’t air in the system, but still wanted a reliable reading from the driver’s seat. I ended up pulling both sensors and brushing them clean. After reinstalling I replaced all of the wiring between the sensor and the gauge, ensuring that it followed the original path. No more issues.

[spider2081]

I might be missing this in your replys but have you disconnected both sensor wires from their senders to see what the gauge indicates. I think with both removed the gauge should read 0. IF it does not I think the issue is in the wiring or in the gauge itself.