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View Full Version : Electrical Thermo Time Switch burnt up while connecting cooling fans


DeLorean937
03-01-2014, 02:02 PM
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
03-01-2014, 02:57 PM
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
03-01-2014, 03:49 PM
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
03-01-2014, 04:26 PM
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
03-01-2014, 08:22 PM
Does a bad TTS result in poor cold starts?
opethmike
03-01-2014, 08:30 PM
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
03-01-2014, 09:32 PM
[QUOTE=It turns out the PO cut the connection to the switch and wired it to install backwards?...[/QUOTE]

Why on earth.......
jawn101
03-01-2014, 10:35 PM
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
08-19-2020, 11:55 PM
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
08-21-2020, 09:22 PM
bump; anyone measured it?
dmcman73
08-22-2020, 08:47 PM
bump; anyone measured it?

Source: http://support.delorean.com/kb/a60/cold-start-issues.aspx


Thermo Time Switch Diagnostics:
Testing the TTS is a bit counterintuitive as it appears to have two connection pins but actually uses engine ground as a third connection. To test with an ohm meter, set the meter to a low (Rx1) range. Unplug the TTS and note that there are two pins on the connector. One of these pins is the connection to the heater, the other is the connection that grounds the Cold Start Valve when cold. The heater should measure about 50 ohms to ground, and the switch connection should measure a dead short (0 ohms) to ground when cold and open (infinite) to ground when hot. NEVER apply a test voltage to the TTS.
SBL
08-24-2020, 05:31 PM
Got it.

It has a cracked connector area, and came back from DMCFL pugged in backwards, so it all makes sense.

Steve
Azar
06-20-2021, 07:53 PM
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?
I have exactly same issue but my readings are 30 Ohm and zero when cold and 60 Ohm and 120Ohm when hot (above 95F). I am also afraid that 120Ohm is not enough and cold start valve is flooding the engine. This may have possibly led to the petrol finding its way in to the oil diluting it and reducing the engine lubrication.