Manager Forum

On middle 90s and up Chrysler products minivans with the 3.3L and the 3.8L engines, they have a little gizmo under the dash in the fuse panel called a "Positive Temperature Coeffieient". Does anybody know what they are and what the purpose of it is and how does it function? I got a 95 Town & Country no start that is drivin me up a wall and right now with the workload I have, I need to get this thing back on the road. Somehow in the diagnosis, I come across this thing in the troubleshooting sequence. But I am stumped.

Thanks for your help!

no idea, (blind animal running around in woods) but if you can give me some symptoms and scanner readings i may be able to help you with your diagnosis. the quick basics are the asd , power relays or the distributer or plug at the dist. if you have spark and fuel i'de see if the t/belt jumped or on the "way out there" possibilities i would check for a cracked or warped flex plate or water in the fuel. i've also had a fair share of issues with the power distribution bpoxes near the battery.

Well, for starters, no dtc in pcm, fuel pressure is 52psi koeo. Scan tool indicates engine rpm, we got fuel injector pulse but no spark. ASD relay is working, got 12 volts to the coil pak, however when doing my coil driver test #3 fails even at the PCM. This is almost certainly indicating a faulty PCM although my testing is somewhat inconclusive at this point as to why it will not have spark if the other 2 coil drivers are working and sending the signal to the coil pak for spark. After I finish this Dodge pk tk I need to go back on this one and find out what the problem is.

They are circuit breakers built into the fuseblock. Called PTC's for short. They can and do fail. Test them just like any other fuse or breaker.

Well that seems to be what they are. Are they designed to trip/blow when a certain temperature on the circuit is reached due to overload or what is their purpose? I mean, there is fuses on those circuits already and according to logic there should not be a need to protect a fuse with another fuse/device, or is there some other design to these things? Basically I guess is I'm looking for info as to what they are there for and how they function. It's interesting that when I called the local dealer the techs in the shop say they have no idea what they do or what they are there for.

Regarding the 95 T&C, there is an internal short on the PCM on the coil driver circuits and I need to find a replacement.

Think of them as a thermal limiter. You can create heat in a circuit before actually tripping a fuse. Keeps things like window motors and power seat motors from overheating, even though they never exceed their amperage draw.

If it operates as a thermal limiter (which is about what I suspected), then I wonder why not call it that instead of this fancy name as a positive temperature coefficient? Reminds me of another thread on this forum about name changes and definitions of various components.

Thanks for your clarification on this issue. Appreciate it when those that know more than me speak up!

Are we having fun yet?

it's a sighn of the times. did you know that when you go to a full service gas station the person that puts the gas in your car is a "petroleum transfer engineer". it was explained to me that the limiters will protect from a spike.

SO? What was the FIX!

New PCM and the thing fired right up and runs fine. Kinda expensive unit but customer wanted his baby back an running.