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#1
10-05-2008, 10:02 PM
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69 GTO Temp Gauge Pegged
Checked through the forum and saw a few items on this but didn't know if it applied to my 69. Anyhow, I've got gauges and the fuel, oil pressure and Gen light work fine but the Temp gauge is pegged even when I disconnect it from the sending unit (green wire under hood). Is there a way I can test the gauge before going to the extreme of pulling stuff to get to it.
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#2
10-06-2008, 01:40 AM
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Not really, if you just want to test the guage.
Follow the green wire back and make sure it hasn't gotten grounded out somewhere. Look for rubbed bare, burnt, pinched or bolted under something. Last edited by "QUICK-SILVER"; 10-06-2008 at 01:46 AM. |
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#3
10-06-2008, 02:24 PM
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If the wire is shorted to ground, the gauge will "peg" to the hot side. You might try an ohm meter from the green wire to ground. It should be more then 0 ohms.
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#4
10-06-2008, 06:31 PM
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The additional steps I've taken. Disconnected green wire from the sending unit, checked for short between it and ground, read 54 ohms and would assume I'm reading the gauge itself. Validated continuity on green wire from clip that attaches to the sending unit to the connector at the firewall. Validated dead short between intake housing and outside of sending unit. Checked to ensure the sending unit wasn't shorted between outside and lead that wire clips on (open). With wire disconnected from sending unit, turned ignition on, no movement in needle and it stays pegged. Something else I noticed today, parking brake light doesn't work. It definitely used to and it's very rare, like once a year, that I'll set the parking brake. Checked the bulb and it test good. So I'm not sure if there's something in common here or not. Although based on the "circuit card/film/plastic" piece that's on the back of the gauges I would think I would have other problems since the common connection routes to all the other gauges, ie: fuel, temp, and oil. My guess is the common connection to that light is a positive and the other lead from the light going to the wiring harness that seats in the back connects to the switch in the floor that supplies the ground when you set the brake. Anyhow, I've attached a pic of the back of my gauges. Does anyone know which lead is the one coming from the sending unit that goes to the gauge on the right side of the pic? I could validate continuity and check to see if it's shorted without having to pull anything. Or of course if you have any other thoughts on what else I should check I'm game. Last edited by torqhead; 10-06-2008 at 06:37 PM. Reason: Forgot to attach the pic... :) |
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#5
10-06-2008, 07:47 PM
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Can't tell you which one, without a better picture of the printed circuit.
It's not the lower, it's a shared ground. Leaves left and right, ones battery voltage and the other is sending unit. Measure the resistance across the white/flat/wire-wound regulator. Remember it could be bad. Disconnect battery, ground one terminal with a jumper and check resistance on the sending unit wire. Swap ground to the other terminal and check resistance on sending unit wire. One will match the resistance of the regulator (white/flat/wire-wound) Best I can do without a GTO cluster. Wiring diagram doesn't help. OR OR OR Much easier Probe the green wire at the plug-in to the left and right terminals. Look for the resistance of the regulator. Good luck Take it easy on the neck I can't do that anymore |
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#6
10-06-2008, 08:10 PM
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Here it goes... Picture attached has leads numbered 1-4. 1 is shorted to ground. 2 gets 12v with ignition on. 3 is not ground or 12v, no reading (thinking this may be an issue). 4 is the lead that comes from the engine bay (green wire) and validated at the back of the gauge that it is not shorted to ground. And of course your making me go back there again cause I didn't check the resistance between 1 and 3....  ) I should have thought of that too...And oh by the way, I pulled the bulb out of the socket for the brake light. Checked it again, good and this time when I put it back in I wiggled it back and forth and put it in it's tightest position when I rotated it in. Now it works, figure it just wasn't making good contact. Now back to laying around again. I'll post my results but maybe this gives some insight. |
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#7
10-06-2008, 08:23 PM
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Alright back to the pic.
1 and 3, 39 ohms - 1=ground as I said earlier 3 and 4, 86 ohms 3 and 2, 39 ohms |
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#8
10-06-2008, 10:38 PM
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I'm afraid it's time to go deeper.
Check out 2 to 4. If you have the terminals diagnosed correctly, power across 2 and 4 creates the electro magnet that moves the needle. You're making me hurt Will check back in tomorrow |
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#9
10-07-2008, 07:18 AM
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I have similar issue with my 70 GTO and posted problem on tech forum last week. I'll try the ohm reads you did and post results.
http://forums.maxperformanceinc.com/...d.php?t=575922 Hope we can figure this out. Let me know if you get it working and how |
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#10
10-07-2008, 09:38 AM
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2 to 4 is 52 ohms. Terminal 3 is buggin me though so I checked again... Must have not had a good ground when I checked it for power, ign on it show a little over 6 v. I also checked 4 with ignition on and it showed 10.3 v. Last edited by torqhead; 10-07-2008 at 09:54 AM. |
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#11
10-07-2008, 11:40 PM
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Thinking Been looking for some info Last edited by "QUICK-SILVER"; 10-07-2008 at 11:52 PM. |
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#12
10-08-2008, 12:54 AM
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I found this link on the net that describes how a gauge works.... Although I'm trying to wrap my head around what could be the issue. http://www.lectriclimited.com/freque...stions.htm#E01 |
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#13
10-08-2008, 02:59 AM
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Does your needle ever drop back down, key off? cranking? Always been this way or just happened? Let me know about above, got something you might want to try. |
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#14
10-08-2008, 10:02 AM
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#15
10-08-2008, 01:06 PM
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Guage may have bit the dirt.
Unhook battery, I've used 9 volt radio batteries doing this. Try reversing polarity across the terminals, should force the needle back. Might tap the back of the guage while doing this, one of the terminals may have lost contact, pegged the guage and it's just stuck. While you're in there, take a jumper wire and try adding a good ground on the ground lug. May break the nut loose and snug it back. Something to try Hopping for the best here |
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#16
10-08-2008, 06:11 PM
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#17
10-08-2008, 11:39 PM
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Sounds about right, what you have to do to get the cluster out.
Good luck with it. I'ld try to find another guage, before I took it apart. Trying to remember what those guages looked like. Wondering what the chances are that the needle has come loose and slipped on the post. Might be wishful thinking. |
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#18
10-09-2008, 10:24 AM
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#19
10-09-2008, 10:52 PM
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On my 68 GTO I can remove the gauges without removing the dash. Just remove the bulbs, nuts, and screws and move the circuit board out of the way and pull the gauge set out. I think the needle has gotten stuck on the opening of the face plate. Mine did the same thing. Just bend the needle down a little before re-installing the gauge set. You can also test the gauges outside of the dash using jumper wires. If you need the info I can write it here.
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#20
08-24-2009, 02:09 PM
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