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Temperature Gauge Sender Question


techboy
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Ok, so bottom line I'm trying to get my car to run better. I was talking with helrazr70 at a meet yesterday and he was telling that some of the cars have two 2-pin CTS style units in the manifold. I know the vertical sensor is always the CTS, but after doing some research tonight I found this graphic (below) from another Starquester on the board and it states on #1 that "also a 2-pin type on some models", just like helrazr said. So, therein lies my question ... which models? I was under the assumption it was a A/T M/T difference, but after some researching tonight, that doesn't seem to be the case. My car had a single prong sensor in it when I got it, and I replaced it w/ a new single prong, but my gauge still doesn't work (and I swapped clusters too) and the car still doesn't idle right either. I know the obvious answer would be to take a look at the wiring harness plug, but the P/O hacked a lot of the wiring harness and I've had the joy trying to figure it all out and solder everything back together. The clip ends are long gone :angry:

 

http://img535.imageshack.us/img535/7038/intakesensors.gif

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It would probably be helpful to tell you my car is a M/T as well.

 

1988 Manual Transmission, Correct. Is the Yellow/Green wire hooked up to it? That wire goes direct (through a connector) to the Dashboard Temp. Gauge. P.S.This sender is not a sensor. It has nothing to do with your cars idle. It's sole purpose is to read your Coolant temp. and send it to the Temp. Gauge in the Gauge Cluster. You might want to go here: http://www.starquestgarage.com And download the Factory Service Manual. The Electrical section will show you where all the wires hook up.

 

Bill

Edited by Caliber308
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Digital AC cars 86-87 have a temp switch on the heater core so the fan doesn't come on when the coolant is cold and blow cold air at you when you want heat. 88-89 cars had that switch moved to the gauge temp sender. Only 88-89 cars had the 2 prong temp sender. One prong is for the gauge and one for the HVAC controls. Your sig suggests you are working on an 88 car. Therefore you should have a 2 wire connector for the temp sender. Try switching the wires.
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1988 two pronged Coolant Temp. Senders are not needed on a Manual Transmission set up.Automatic,yes.The lower part of the two-pin T sends a ground to the overdrive relay after the engine warms up. (Only has a use with A/T cars).

 

Bill

Edited by Caliber308
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I think they started using the two prong sensor in the intake for the a/c in 85.5. Harness connections for this have both terminals and the unused one is just folded back and taped up. They changed the a/c box under the dash 8/85, there's differences in 85 to 86 model cars on other parts.
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I'd look into you having the wrong wire on the sensor. If you ground it out using a test light with a bulb in it, the gauge will slowly go to the top. If it doesn't you got the wrong wire or the gauge is bad. That doesn't have anything to do with the fuel unless you have the gauge and CTS wires backwards then neither would work since the CTS wire uses the ECU ground not body ground. Taking the plug off the ECU and those two sending units and some testing would be a good idea its just four wires you are looking for and three of are yellow with some faded hard to tell stripe and a black wire. Just unwrap the harness starting at the intake until you find them they are in there.
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Thanks for all the replies guys, very helpful.

 

I understand that the gauge has nothing to do with idle and the CTS has nothing to do w/ the dash gauge. I mentioned it b/c the car runs rich at startup/stumbles AND the gauge doesn't work ... so, I'm thinking maybe the wrong wires are going to the wrong sensors.

 

I think what I need to do is what Indiana said in the last post and strip these wires back as far as I can and trace them. They are exactly as described, faded and brittle ... should be fun.

 

I'm meeting up w/ someone local tonight who has a completely stock setup like me, I'm hoping to look at his engine bay/wiring harness and do some comparing. I'll post up if I find anything or have another question.

 

 

And then finally, to wrap up the other question ... whose right .... Caliber or ucw? Do all 88/89 have a 2-pin sender or just A/T's?

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I went and looked under a few hoods.

 

The single is up to 87 then in 87 both plugs are present. The single wire just goes in and is tied into the other wire wrapped up. Remember this is when the car went to one ECU at the same time they changed from the 83-86 fuel system of two same sized injectors to the 87-89 primary/secondary and its why you can swap ECUs for those three years where before there was a different ECU for automatic cars 84-86 and a different harness that included that two terminal plug. The 83-86 manual trans cars only have one plug. I didn't look under the hood of any 84-86 non intercooled cars that were automatics to see if there was a loose unused single terminal but I'm going to guess there wasn't. In 87 they changed for a common plug but there was no widebody automatic cars until 88 then for 88/89 there was only the two terminal plug in the harness and all 88/89 cars used that two prong sending unit but so did most 87s. The resistance range of the gauge half of that sending unit is the same for both its why you can swap them same goes for the gauge all are the same just a different look in some clusters they were L shaped not round.

 

 

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1988/89 cars used Two-Pronged senders. I checked out the 1988 FSM Section 23 (Electrical section) on Starquestgarage.com. And that source of information calls for this: The wire that goes from the top of the "T" (cross spade) in the Two-Prong sender to the Dashboard Temp. Gauge is Yellow/Blue. (It looks like someone changed it in the FSM on Starquestgarage). 1987 models used the Single-Pronged sender and the Yellow/Green wire to the Dashboard Temp.Gauge. So, after doing this research, I would suggest using the Two-Pronged Sender on your 1988 wiring set up, even though you don't need the other wire (Yellow/Green) hooked up to the bottom prong for a Manual Transmission.If you Download the 1988 FSM from http://www.starquestgarage.com and search through Section 23 in the wiring diagrams, you will see what i'm referring to.Another good source of information can be found here: http://www.starquesti-x.net in the SOS Manuals under Senders and Sensors.

 

Good Luck. Hope this information helps,

Bill

Edited by Caliber308
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Yeah, I do have the FSM downloaded, and I have a hardcopy. I thought this was the famous sensor though that had the refer to "group 8 electrical" notation and then you go there and it's not there. Maybe that was the Parts Locator (??) Anyway, I meet someone tonight for the first time w/ an 88 manual and they have the 2pin sensor as well. Thanks for the FSM tip. I'm going to check it out now.
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87s have both plugs side by side and depending on the model/options one is not used it just is folded back and taped so it won't dangle. I can take a picture and show one if you haven't seen it before.
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87s have both plugs side by side and depending on the model/options one is not used it just is folded back and taped so it won't dangle. I can take a picture and show one if you haven't seen it before.

 

Agreed. I have both plugs on my 1987 Wiring Harness.One is hooked up, the other is not.

 

Bill

Edited by Caliber308
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87s have both plugs side by side and depending on the model/options one is not used it just is folded back and taped so it won't dangle. I can take a picture and show one if you haven't seen it before.

 

Indiana ... I'd love a pic if it's not too much trouble. I also wouldn't mind seeing what an OEM CTS plug connector looks like and the OEM 2-pin connector. I have on connector still intact, wondering which one it is.

 

I've also been working on figuring out the wiring colors in the FSM this morning. Here's what I think I know so far: There are 5 wires coming from that leg of the harness ....

 

1 - Yellow/Blue - Engine Coolant Sender (Guage)

2 - Yellow/Green - Engine Coolant Sender (Guage) - Dead on a M/T ... overdrive ground on A/T

3 - Yellow/Green - Engine Coolant Sensor

4 - Black - Engine Coolant Sensor Ground

5 - Yellow/White - A/C Temp Switch.

 

How nice of Mitsubishi to use 2 Yellow/Green's in the same harness leg. Ugh. I'm thinking what I'm going to have to do is cut off all the P/O's crappy solder joints and strip back the harness to find the original wires and run new wires to the proper locations, labeling as I go. And maybe, just maybe, the car will run better and my temp guage will work!

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The OEM CTS connector had a molded rubber boot around it about an inch and a half long that's usually hard and part broken off because it went down over that lip on the oval end of the CTS so it was sealed and wouldn't get that connection wet or its completely broken off and maybe just a little bit left over the end of the plastic connector part or on the wires. The gauge plug never had anything like that. You need a picture of that? The CTS connector has a black wire in it, if it has two yellow wires with stripes then that's for the gauge. The single wire is the switch for hte a/c compressor in the thermostat housing top. Edited by Indiana
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Yeah, if you have one available.

 

Here is a link that explains and has pictures of all the sensors on the intake manifold.

 

http://starquest.i-x.net/viewtopic.php?t=1097&sid=50cd4a9fc3e9888e0380d274b9fec7dd

 

For What It's Worth.

 

KEN

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Here is a link that explains and has pictures of all the sensors on the intake manifold.

 

http://starquest.i-x.net/viewtopic.php?t=1097&sid=50cd4a9fc3e9888e0380d274b9fec7dd

 

For What It's Worth.

 

KEN

 

Wow! That link is really helpful and thorough. I found the pic before (as posted in post #1), but never the whole thread. Thanks. I'll printing this out.

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