Hey there. My first post here, but I did read through the back posts first. I am a newbie 87-IROC owner and I must say this place is a great source of knowledge.

I have the same problem with no heat in the car, but I could really care less about the heat. I have other concerns. My temp guage is pinned passed the MAX LEVEL, so I have no idea how hot the engine is getting, but it feels HOT. Not that I touched it, but when you lift the hood you can feel it. So I thought I'd change the thermo.

I changed the thermostat today and still have the problem, of no heat, but I could really care less about the heat. I am solely concerned with the engine temp. Which leads me to my question(s):

1. Can anyone point me to the instructions to swap my guage?
- I have the Chiltons, Haynes and Helms but cannot find the info. Helms page 8C-16 tells me how to identify a bad guage. (Incorrect temp reading) but even with my ounce of knowledge I could have worked that one out.

2. Is this an easy swap?

Thanks for your time. I will tackle the heat problem when/after I fix the temp guage. Many thanks...

-Jason

 

the needle will be pinned if the sensor has gone bad or has an electrical short in the circuit

the sensor, if you weren't sure, is in the drivers side cylinder head... follow the wire along to see if it's damaged

Welcome to our board...

 

Thanks for the Welcome and also for the info...

Do I have to remove the throttle body and Plenum to see the sensor and/or wire?

-Jason

 

I have a carb so I'm not sure where the wire is run on your TPI setup. The sensor is located between the front two pipes (#1 and #3 cylinders) of the exhaust manifold an the side of the head... not the top

 

Ok. I think I found it. It may be an open circuit. I have a Dark Green wire (as indicated in Helms Elec Suppplement) , in its own little plastic conduit just wrapped around the A/C mounting bracket a few times. I unwrapped it from the bracket and it has a metal clip connector on one end. Looks like someone had just stuffed it up in there to get it out of the way. Thanks for your help.


I am going to continue trying to locate the sensor.

 

my wire is green as well... the sensor is about 1" in diameter and protrudes about 1 1/2"

 

Your tem sensor for the gauge should be on the drivers side head on the outside by the exhaust manifold. In between cylinders 1,and 3. I can't remember what color the wire is. If you find out which wire it is let me know I have to re-run that wire. It is missing from my current car.

 

I don't think I found it. I did connect the green wire though that was disconnected. It was a Dark Green wire with a tiny clip that slips sideways on to a circular sensor. It is underneath a tiny heat shield that protects it from the heat coming from above.

I had to get under the car in order to see it properly. But once I knew where it was, I could connect it from the top by feel. I took my light probe and tested the little stud and it is getting power, but my temp guage is still pinned.

I looked in the Helms manual again and found another section in the regular shop manual where it talks about CODE 14 and the Coolant temperature circuit. It lists the sensor as having a Yellow (Circuit 410) and Black (Circuit 452) two pin connector.

I don't have a scan tool yet, so I am unsure if I am flashing a CODE 14. Next Pay Day.

What the heck did I connect with the Dark Green-Single Pin connector if it wasn't the temp sensor? Thanks for the continued support.

*Edited for articulation and specifics.

 

The other sensor which the book is refering to (the one with two wires) is the temp sensor for the ECU (aka-Computer). This sensor has nothing to do with the temp gauge in the dash. The wire which you hooked up (green with a little slide clip) is the correct wire for the temp gauge and it sounds like you hooked it up to the correct sensor/sending unit.

So, don't worry about the other temp sensor with the two wires (at least not for this issue which you are having).

Later,
Mike

 

I agree with Nitro...

When the green wire was shorted out against the engine block it would have caused the guage to slam to the right very quickly. It may have jambed the needle in that position. Also... the needle is run by a sensitive electrical potentiometer... it doesn't like being exposed to that kind of a shock and may now be out of spec.

Try tapping the glass on the dashboard to get the needle to fall back... if that doesn't work remove the panel and give the needle a gentle tap with your finger. If that doesn't work replace the sensor in the head. If that doesn't work, and you aren't comfortable with electrical work, it's time to take the car to a garage that does engine electrical work.

 

Remove the front of the guages and clearance the side of the guage so that the needle cannot get stuck there. I was having the same problem for a while until I took it apart and fixed it.

 

I did remove the cluster bezel so I could mess with the needle. And I am getting closer to the source of the problem. Maybe the next time someone starts their car they could do me a favor and just look closely at their temp guage as they move through each key position.

1. LOCK
2. RUN
3. START
4. -Engine Running-

Here is why I ask. The needle was jammed up into the side of the guage and when I free it up, it drops into position. But there is still a problem I believe.

1. I free the needle from the uppermost corner of the guage and it drops into position.

2. I turned the key from "Lock" to "Start" and the needle clicks into the proper position, as do the rest of the needles in my cluster.

3. When I slowly (or speedily) turn the key from "START" to "RUN" and watch the temp needle. The needle slams up into the uppermost corner of the guage again and gets stuck. I continue to turn the key until I engage the starter and the engine cranks, then let the car key rest in its RUNNING position.

4. I take my finger and help the needle out of the corner of the guage and it drops into the proper position, with an accurate temp reading.

If everyones needle slams into the uppermost position right between the key position of RUN and START, then I guess I need to make some guage clearance because it is clearly getting stuck up there.

 

Mine did that same thing. I just clipped the end of the needle just enough to where it would clear.

:hail:IROC-Z

 

yea, mine does that too, I still haven't figured out a solution.

 

Hmm. That is interesting. I didn't really want to cut the needle tip. Anyone have any ideas about the nature of this anomoly?

Thanks for posting, its nice to know that others have the same problem. Just wish that we could find some more information about this.

 

I have 87 IROC experiencing same problem.
I glued a stopper on the guage face. When the needle hits the stopper it resets and works fine.
When I have time I will check all the wiring.

 

i actually had this problem, but it was worse that a ground. my thermostat got stuck. my heat stopped working. then the temp gauge went alllllll the way up, nearly 300 degrees. luckily nothing was damaged. replaced it with a 160 therm and was all better. swore i heard the death of my radiator. think of the sound crush a giant beer can. yeah, that. maybe might wanna replace your thermostat? not an expensive fix and wont hurt

 

CDN-

I was thinking about doing something similar, but there must be a reason why this is happening. That sounds like a good quick fix though, and I'll probably resort to something similar until I can understand exactly why this happens.

My friend has a multimeter that can log results for future analysis, and I am going to connect it for a few sequences of:

OFF
RUN
START

OFF
RUN
START

to see if I can find out what is happening and then why.

 

I haven't gotten the multimeter from my friend yet, but I modded my temp gauge. I used a Dremel Flex Shaft attached to a cut-off disc and removed a small part of the temp gauge rim, where the needle was getting stuck. It was pretty simple and turned out clean.


With the glass and bezel on you can't even tell anything was done. Just thought I'd let you know. Once I get the logging multi-meter, I am going to do some testing, but this is good for now at least.

 

Thanks to everyone for their help. It was with your help that I got this problem fixed. Many thanks.

-Jason