1988 left front of eninge between 1 and 3 plug
THere are 2. one for the gauge, and one that reads for the fan. the gauge one is located by the firewall, while the other is near the coolant thermostat housing.
Gm. did not use a crank shaft sensor in 1988, It had a distributor that done everything.
If your 1988 Chevrolet Celebrity has the V6 engine the oxygen sensor is in the middle of the exhaust manifold nearest the firewall. If you have the 4 cylinder engine the oxygen sensor is located in the exhaust manifold just above the exhaust pipe flange.
If you find the wire to the switch near the thermostsat.Then earth the single wire to the engine and if the gauge inside lifts to max then the wiring and gauge are ok, then its def your switch. Check your fuses for your gauge and check condition of wire coming from temp sensor on block. Sometimes they come disconnected or break from heat.Check continuity from gauge to sensor,if none replace sensor.
intheintakemanifold
There are two temperature sensors. One is under the #6 intake and sends signals to the temperature gauge. The second one is in the thermostat housing and signals the ecm module.
Purple
The 1988 Honda Accord coolant temperature sensor can be found on the front of the engine. The coolant temperature sensor will be a few inches above the thermostat housing.
On the housing where the thermostat bolts on, just above the water pump and below the upper rad line (the suppily), there is a temperature sensor. Remove it, install a Tee into the fitting and reinstall the temp sensor in one of the legs of the Tee, and the sensor from the after-market gauge in the other. run the sensor wire through the firewall and up to the gauge in the dash. Connect the lights to the gauge and there you go. On my 4cyl there was another temperature sensor at the back of the head (up close to the firewall) that went to the dash idiot light. I suppose you could pull it, and install the sensor there. But I kinda liked having the idiot light as a backup. The sensor in the front that you are teeing into is the one that measures engine temp for the computer, so make sure that you reinstall it.
It on the back of the coil packs going into the side of the block.
Chevy did not use an Idle Air temperature sensor on that year.
Behind the timing belt cover.