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Username Post: 1989 Chevy 4x4 coolant temp sensor wiring        (Topic#272692)
Tarheel308 
Forum Newbie
Posts: 32

Reg: 04-22-09
11-27-11 07:41 AM - Post#2162247    

I have a 1989 Chevy 4x4 with the 5.7 and someone has added an aftermarket coolant temp gauge with the sender located between #1 and #3 spark plugs. I'd like to see if I can repair the original and was wondering if it had a one-wire or two-wire setup. I found a single green wire on top of the intake and was wondering if that may have been for the original sender. If this is the wire for it, is there a way to check the gauge using it without taking out the instrument panel?

Thanks
Buddy


 
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someotherguy 
Moderator
Posts: 25967
someotherguy
Age: 44
Loc: Texas
Reg: 08-01-03
11-27-11 07:47 AM - Post#2162248    
    In response to Tarheel308

Hey Buddy,

You'll find that most likely that single green wire is your original dash gauge temperature sender wire. The sender on the head is a single wire design but depending on year may appear to have a two wire connection - but only one pin is populated inside the socket.

The circuit operates on range of resistance so be sure any connections you make are clean and tight; soldering it and using heat shrink tube to protect the joint would be best, but a well-applied crimp connector would suffice in a pinch. The more resistance on this circuit the colder the temperature will read so you can gather from that the importance of a good connection.

(The coolant temperature sensor, CTS, is actually the one on the intake manifold next to the thermostat housing; it feeds data to the ECM not the dash gauge and is a two wire setup.)

Richard
94 C2500LD / 97 Suburban LS1 / 06 300C SRT8
Check out my truck shop projects


 
Tarheel308 
Forum Newbie
Posts: 32

Reg: 04-22-09
11-27-11 07:53 AM - Post#2162250    
    In response to someotherguy

Thanks for the fast response Richard. It seems they removed the orginial sender and replaced it with a manual one. I wonder if I ground the green wire will it peg the gauge so I know its working? I saw the sender located beside the thermostat housing on the intake and it looks fine. I just ordered a Chilton repair manual so I can see the wiring diagrams.

Also, does anyone know what the resistance range is or do I need to know this when looking for the original sender?

Thanks
Buddy













Edited by Tarheel308 on 11-27-11 07:58 AM. Reason for edit: No reason given.

 
someotherguy 
Moderator
Posts: 25967
someotherguy
Age: 44
Loc: Texas
Reg: 08-01-03
11-27-11 08:22 AM - Post#2162260    
    In response to Tarheel308

Open circuit will show a gauge totally dead; short to ground will peg it way past the upper end of the scale as there's no "stop" on the gauge.

No need to be concerned with the resistance range when getting a new sender, but since your truck is an '89, it's possible there may be more than one choice for the sender based on gauge or warning light (the squarebody trucks were available in '89 still and I'm guessing may have still had a warning light style dash on base models.)

The other thing to be watch for is that they actually give you the sender for the gauge, instead of the one for the computer. If it has two pins in the socket it's the wrong one. Also, your '89 probably has the old style round lug type connector that a spade terminal slips over. At some point later they switched to a weather-pak style connector that looks nearly identical to the CTS up on the intake.

Richard
94 C2500LD / 97 Suburban LS1 / 06 300C SRT8
Check out my truck shop projects


 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3090

Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
11-27-11 08:23 AM - Post#2162261    
    In response to Tarheel308

This is from a 1993 manual.
It may, or may not, be the exact same specs.

Dash Temp gauge testing:
Unplug the sensor and the gauge should go all the way to the COLD end of the gauge.
Grounding the wire to the sensor should make it go to the HOT end of the gauge.

Dash Gauge Temp Sensor
1400 OHMS – COLD
55 OHMS – HOT

For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If the it has been altered from stock let us know about that too.


 
Tarheel308 
Forum Newbie
Posts: 32

Reg: 04-22-09
11-27-11 11:34 AM - Post#2162312    
    In response to someotherguy

Thanks for all the info guys. Richard the green wire has a grey plastic end and looks similar to the end on the wire to an electric choke. I am going to test the gauge to see if it works, if it does then I'll try to locate the proper singe tab sender.

Againg thanks for all the help


EDIT
The truck I have was the new body style with the cresent(moon) shaped gauges. I tested the gauge but it didn't move much, maybe a quarter inch. I did notice that went starting the gauge (temp) doesn't move until I rotate the switch past the "ON" position and towards "START" but the other gauges move when the switch is in the "ON" position....

Edited by Tarheel308 on 11-27-11 12:03 PM. Reason for edit: No reason given.

 
someotherguy 
Moderator
Posts: 25967
someotherguy
Age: 44
Loc: Texas
Reg: 08-01-03
11-27-11 11:45 AM - Post#2162314    
    In response to Tarheel308

Good deal; glad to hear they didn't chop the connector off, makes your job much simpler.

The original sender for your year model had a round tab that the connector would slip sideways on top of; the replacement sender will likely have a single lug terminal sticking out, like this:



After looking it up on your year model I was correct; they do also list one for a warning light type dash instead of a gauge, so be sure they get you one for a gauge application.

Richard
94 C2500LD / 97 Suburban LS1 / 06 300C SRT8
Check out my truck shop projects


 
Tarheel308 
Forum Newbie
Posts: 32

Reg: 04-22-09
11-27-11 12:06 PM - Post#2162318    
    In response to someotherguy

UPDATE
The truck I have was the new body style with the cresent(moon) shaped gauges. I tested the gauge but it didn't move much, maybe a quarter inch. I did notice that went starting the gauge (temp) doesn't move until I rotate the switch past the "ON" position and towards "START" but the other gauges move when the switch is in the "ON" position....

Thanks again
Buddy


 
someotherguy 
Moderator
Posts: 25967
someotherguy
Age: 44
Loc: Texas
Reg: 08-01-03
11-27-11 12:11 PM - Post#2162322    
    In response to Tarheel308

With the sending wire grounded and key on, the gauge should have gone way past the overheated mark. It's possible the gauge is bad or there's resistance in the circuit due to damaged wiring, oxidized connector at the dash plug, etc.

The gauges are replaceable separately within the cluster and that may be the best choice if it turns out the gauge itself is bad; finding another good 88-90 cluster with every gauge working in it can be a little tricky - even moreso finding one that the speedometer is calibrated same as yours.

Richard
94 C2500LD / 97 Suburban LS1 / 06 300C SRT8
Check out my truck shop projects


 
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