Gregory what is the resistance for temp guage?

countryguy53

countryguy53

Daily Driver
I swapped my temp sensors( on stat housing) last week and it ran fine then this week it started acting up again the same way. I have the sensor out of my spare engine i thought about swapping them out but i figured i'd check to see what the values they should be. Your last post on this subject kinda confused me 2500-300 cold 300-250 ohms hot. Is this right? Both of mine are around 3 to 4Kohms cold. pls let me know and is this the temp sensor that Vicks wants 68.50 for? tks Gene
 
Can't help with specs but....

Gene,

I don't have the sensor specs in front of me at the moment but I'm gonna go out on a limb and suggest that, since both the sensors you have read the same, the problem may well be in the connection or wiring.

CTS problems are common in my world, but they can often be traced to oxidized contacts in the plug or oxidation in the wiring leading to the plug.

I just got done going through the lighting on my new X, trying to resolve some intermittent problems. Turns out the positive contacts in the sockets had oxidized enough to prevent a reliable connection from occurring. Perhaps the same thing is happening with your CTS.

Try cleaning the inside of the contacts in the plug with a sliver of 1000 grit sandpaper, or spray them out with some Caig DeOxit. Then apply a contact enhancer like Caig Gold or Stabilant 22 and see if that helps.

Of course, there's always the chance the oxidation has worked its way into the wiring leading to the plug for the CTS. It's not uncommon for the CTS to weep a bit between the plastic and the brass, and over time that moisture can wick its way up the wiring, causing corrosion several inches into the harness. In such cases it's best to cut the wires back far enough to remove the oxidized wiring and replace the connector and bad wiring altogether.

HTH,

///Mike
 
One other thing Gene...

Be sure the tiny washers located under the small brass screws on the back of your gauge cluster (under the temp gauge itself) aren't corroded.
That could cause you trouble too...
 
i misspoke its the sensor on the thermo housing

i did write the temp guage, but i ment the time/temp sensor on the engine. I have cleaned the contacts and was thinking about putting a resistor in the place of the temp sensor for a test. to see if its the sensor values that are wrong on or if it was possibly the wireing. i didn't have this problem before i did the rebuild so i figured it must have been the wiggling and giggling of the removal and replacement of the engine that caused the change. i'm hopeing Gregory will have the resistance values so i can try my test. I will call Vicks to see if they have the values also today. thanks for the input Gene
 
Temp Sensor Values

Values are:
7,000 to 12,000 OHMS at 14ºF
2,000 to 3,000 OHMS at 68ºF
250 to 400 OHMS at 176ºF

I have several 270 OHM resistors that I keep in my car's spare fuse container for "limp-home" situations. Just unplug connector at sensor, insert resistor wires into connector socket, and drive. This simulates a warmed-up car's resistor signal and will work if your sensor is bad.

Temp sensors are pretty common, I recently bought one at my local FLAPS (friendly local auto parts store) for $18.

It's best to test between terminal 13 on the ECU harness plug (goes to sensor) and ground. You can also test at the sensor itself but this does not test the wiring.

Be sure to double-check your grounds, they are the very important other end of the equation. The ECU ground at ring terminals on the head. The sensor does not ground through it's threaded mounting, so sealant may be used on it, but it should seal simply with a new crush washer.
 
Countryguy.

I checked my Vicks catalogue. on page 34 in the F.I. components square the sensor is listed there. # 33-2601 $ 21.00 ...............
To clarify there are three temperature sensors on the f.i. system.
#1 The thermo-time switch near the spark plugs, it controls the cold start valve.
#2 The sensor for the temperature on the dash guage.
#3 And the one you are working with at the thermostat.This one controls the amount of fuel injected as the engine warms up. This one as pointed out to me a year or two back by Gregory Smith, can really make it work terrible, and indeed sounds like your problem. If you order it make sure you specify the sensor at the thermostat and the # as you may get the other one instead. Good luck.
 
This might help avoid confusion...

I try to use the right terminology. :nod:

The Thermo-time switch is a switch. Like the radiator fan switch. It does not communicate with the F.I. ECU. When the engine is completely cold, below 95ºF, it allows current to the cold start valve/injector for up to 8 seconds.

The part that signals the dash coolant temp. gauge is a sender. Like an oil pressure sender or fuel level sender. It does not communicate with the ECU. Accurate readings can be helped by clean connections on the engine and at the gauge, replacing the steel gauge mounting washers with brass ones is a good idea.

The Temp Sensor II for the F.I. ECU is a sensor, as in it senses a range of coolant temperature conditions and signals the ECU what those conditions are. What makes this sensor important is it determines most of the mixture setting, and can override the O2 sensor if the resistance values it send are too far out of whack.

Hope this helps! :geek:
 
harness check question

Gregory, i found a diagram of the harness that connects at the ecu, should i try to read thru the sensor or short the connector without the sensor in line? the diagram i have shows a direct short to ground from 9 and 13, but 13 goes thru the sensor. With my sensors reading the way they were i'd say it should read 3kohms at 68 degrees. I do have a spare ecu and thought about swapping them to see if the problem follows. AAAhh i love having spare parts car...... i'll grab some 270ohm resistors just in case also... i should have some 1/2 watt ones around.. I'll let you all know how it turns out.. Thanks for the input Gene
 
If you're concerned about the harness, test with and without the sensor in line. To test without the sensor in line, you'll have to use a VOM at terminal 13 on the ECU plug and one of the sensor plugs.

I usually test just the sensor, and only test the harness if everything else tests good and a problem persists. I personally have never come across a bad wire in the harness, but others have.

I just reread your first post on this and the cold range should have read 2500-3000 ohms cold. Hope that helps.
 
if the connector looks bad

you may want to replace that. it's a standard gm fuel injector connector. if it looses connection when the engine is cold it would run rough and be a little hard to start. as it warms up it would smell like raw gas with blue smoke. if it looses connection when warm it will flood the car out. at freeway speeds it will act like it was loosing revs and then die when you get to lower rpm. it will not restart till the engine cools enough.

it all depends on what issues your having really.
 
checked grounds on cam tower/unpluged ECU

I checked the harness from the ECU to the sensor, also tightened the grounds on the cam tower. Nice solid ground from 9 and 13 if i bypass the sensor3.5k thru the sensor cold. I took a ride today and put 35 miles on it and it ran great, no misses or power loss. I figure it might have been a combination of things that caused a resistance in the sensor line, it goes thru the sensor and to a ground. At the same place #9 is tied to ground according to the schematic i have from the link below. I did find a few 270ohm resistors to put into my parts kit in the trunk. Thanks for the input guys. Hopefully its back on the road again. Gene
 
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