So heres the deal, i have a 97 neon dohc, and hoping someone can point me in the right direction. This motor was swapped from an older sohc model, which the motor is either a 97 or 98. When the car starts the heat guage sky rockets all the way to the top, and the service engine soon light dings like crazy. If i turn the car off, it resets and only goes up about 1/4 of the way, every time. Also my speedometer is off, i could be doing 70, and my guage will drop right to 0, but then it will resume at 70 eventually, but every now and then will hit 0, or some other random speed. Main concern is the heating problem to make sure its not a big deal. I replaced the thermostat and the temp sender looks to be new, from the previous owner. Ive driven the car 2 hours straight and theres no smoke or sputtering from the engine, so im assuming that theres a faulty connection of some sort. Also, when it says my temp is that hight, my fans arent even on..so im not sure how to troubleshoot this, is there a way to test to make sure the fans are still working properly, or are the fans just not coming on cause the engine isnt overheating.

appreciate all comments

 

I may be wrong here, but it actually sounds like you have the classic Dash instrument panel going bad syndrome.

https://dodgeforum.com/forum/1st-gen...er-repair.html

This thread describes numerous problems with cold solder joints in the dash instrument panel circuit board that causes the guages (speedo, tach, temp, lights, etc) to either stop working altogether or work erratically at random times. It also describes how to fix it cheap. You just need a solder gun.

If you are not losing coolant, then you are not overheating. Trust me, if your radiator cap were bad, or if your thermostat were bad, or if you even had a pinhole leak, you would know soon enough as your car would show all the signs of overheating with the biggest sign being loss of coolant. Check your overflow tank and if it is at the full hot mark (when hot of course) then you are not losing fluid and most likely not overheating. When cool, the level should be on the bottom mark, and if you take off the radiator cap, it should be full right up to the bottom of the radiator cap fitting.

To test fans, just run a wire from the positive battery post to the fan + connector and if it kicks on and runs at full speed, then it is not a fan issue. You can test the fan relay to see if it is in spec too.

You can easily test the engine coolent temp sensor to see if it is within spec and if it is, then it is not a bad sensor. If both of these are true, then you most likely have a bad instrument panel cluster cold solder joint issue.

 

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You can easily test the engine coolant temp sensor to see if it is within spec and if it is, then it is not a bad sensor.[/QUOTE]

How do you do this?

 

Dip the end of the sensor in a cup of really hot water and as it cools, the voltage readout on the multimeter will change.