Thermo Time Switch burnt up while connecting cooling fans

[DeLorean937]

Ran into kind of a weird situation.

I was connecting up my cooling fans after replacing the radiator, and upon testing them I smelled a burning electrical smell. I looked back back at the engine and found smoke pooring out of the thermo time switch connected to the water pump. Completely melted both connections. Granted I did do a engine rebuild and connected everything back yesterday. I got the car running and dialed in perfect. Only when connecting the drivers side cooling fan it starts to burn. Everything is ok when I run the drivers side fan. Any thoughts?


-Robert

[Bitsyncmaster]

Don't see any reason for that to happen. May have just been coincidence when you tested your fans. For the switch to melt my guess would be a short on the wiring in the CSV circuit.

[DeLorean937]

Don't see any reason for that to happen. May have just been coincidence when you tested your fans. For the switch to melt my guess would be a short on the wiring in the CSV circuit.

Your absolutely correct. I had a spare switch to replace the burnt up one with. It turns out the PO cut the connection to the switch and wired it to install backwards?... Not the way it was suppose it fit into the port on the switch. I only found out when the new switch wasn't all ground down like the original one was.

[DMCMW Dave]

Your absolutely correct. I had a spare switch to replace the burnt up one with. It turns out the PO cut the connection to the switch and wired it to install backwards?... Not the way it was suppose it fit into the port on the switch. I only found out when the new switch wasn't all ground down like the original one was.

Yes, if the TTS is wired backwards it is a dead short to ground when cold. I've never seen one smoke, usually they just kind of pop and go dead.

Normally the problem is the shell of the switch breaks, and then the plug will go on backwards.

[sdg3205]

Does a bad TTS result in poor cold starts?

[opethmike]

Does a bad TTS result in poor cold starts?

Yes. The purpose of the TTS is to tell the cold start valve when to fire.

[kings1527]

[QUOTE=It turns out the PO cut the connection to the switch and wired it to install backwards?...[/QUOTE]

Why on earth.......

[jawn101]

Why on earth.......

Yeah, thats a pretty weird mod to do. In my mind it would call into question the entire engine harness - what was the PO trying to compensate for?

[SBL]

Hate to bring up this old thread, but I cannot find the resistance readings for a property working TTS.

For purposes if identification I will call the 2 pins "top" and "bottom"

When cold, Top shows 0 ohms to ground, as expected, since I suspect this is the switch.
Bottom shows 60 ohms to ground. Suspect this is the heater.

When hot, the top, resistance to ground goes up to only about 180 ohms. To me that seems to be not a high enough resistance to keep some current from flowing to the CSV. I was thinking it would go to wide open or several megohms.

Has anyone made these measurements on a working TTS?

[SBL]

bump; anyone measured it?