[Tony Goat]

Gents,

Looking for some insight from the group. I have a 69 GTO with Rally gauges and HEI upgrade. I've recently had my dash restored (Just Dashes did a great job!) and figured that I'd replace the engine and passenger compartment wiring harnesses while I had easy access to them. In addition to the harnesses, I also replaced the printed circuit as the factory one was delaminating.

Prior to the replacement all of the gauges were working as intended. Afterwards, my fuel, oil pressure, and temperature gauges are screwy.

The fuel gauge is pegged to full while the car is running regardless of the fuel level in the tank. After the car has sat for a few min not running, it will drift slowly down to the F mark. When the ignition is turned back on, it will move back into the pegged position, not quickly or slowly but just move at a normal rate. The gauge was working properly prior to the harness and printed circuit replacement.

The Oil Pressure and Temp gauges are exhibiting the same frozen position just under half way through their range of motion. They don't move at all regardless of the engine operating parameters (running, not running, full temp, cold, start up, ect).


The trouble shooting that I've done so far is...

Check the fuse for the printed rally gauges. Good

Check the ground on the printed circuit. Good.

Check the voltage between the connector and the printed circuit. No reading on any of the connectors.

Check all of the dash lights. Good.

Check the connection at the junction block between the dash and engine harness. Good.

Check the voltage between the oil pressure sensor and supply wire with engine running and not. No reading.

Checked voltage between temp sensor and supply wire with engine running and not. No reading.

Checked the connectors on the steering column. No problems noted.


I've checked all of the areas that I can think of, now I'm just poking around in the dark. Any suggestions would be quite welcome.

Regards,
Tony

[Tony Goat]

So, I guess just getting my thoughts down on paper helped because I just solved two of the three problems I was having. Its is a bit embarrassing, but in less than 10 min I checked my printed circuit closer and found that I had not completely secured it to the gauge housing when I installed it. I tightened up the nuts on that hold the circuit to the gauges in question and they jumped to life. The fuel gauge and temp gauge are now working perfectly.

My oil pressure gauge is still giving me trouble. It is now pegged to the top range of the movement and does so violently when the ignition is turned on. I'll do a little more research on the forum as I remember seeing this somewhere else. Hopefully I can keep this problem solving momentum going.

Tony

[Peter Serio]

Does your oil pressure gauge pointer simply "freewheel"?

Sounds as if all of the factory buffering fluid has evaporated away. If so then the gauge will fail shortly.

[rexs73gto]

I'd double check to make sure they sent you the correct print board for your car. It sounds like they or you have the wrong board. If your not getting the correct readings when your checking them it may be because the path for the circiut is not correct and going to the right place for the dash functions. You may have a board for no gauges or vise verses. Bouble check the board number and make sure it is correct for the dash lay out you have.??????

[Peter Serio]

It would be psychically impossible to install the wrong printed circuit and have all of the threaded studs tightened down as Tony says he has in Post #2.


One common mistake I have seen many times is that underneath each nut you should place a flat washer, (presses down on the copper). I always use new ones as they seem to conduct a lot better than old used, dirty or corroded ones.


May want to check your plug-in at the back of the cluster. The way the wires are positioned in the black plastic is one way for a basic cluster (non-gauges). However the same color wires but a few are in different locations if you have rally gauges.

You may have gotten the wrong dash harness.

[Tony Goat]

Thanks guys, I'll check those things.

The printed circuit, I've compared to the stock one that I've taken off. They're the same.

I'll have to look for the washers, I can't be sure about them.

I'll check the harness plug into the circuit for color wire placement correctness.

Please clarify freewheeling. Do you mean that it moves qucikly and violently throught the range of travel without the resistance that the other seem to have? Then yes, the oil pressure guage freewheels.

Thanks again,

Tony

[Peter Serio]

The pointers for all 3 gauges SHOULD have some physical resistance to them. This is a fluid buffer that is placed in liquid form (2 or 3 drops maximum) around each disc magnet during manufacture; before winding the wire around the Nylon 1/2s. When you have the dash out this is very easy to check, simply touch each red pointer very lightly and you will feel them move but NOT just flop around. ALL GM car gauges run off full battery and charging voltage, i.e. 12 to 13.8 Volts.

The short version is these gauges need some buffering to them or they swing with such force as to tear themselves up. GM designed in a failsafe into their gauges so that they would never stick or jamb, as such the long term failure mode is the "airplane propeller effect."

[Tony Goat]

Well, looks like I'll be pulling the dash again for a gauge rebuild. I'll wait until winter anyway. Thanks for your help and out of curiosity, what's your turn around time for a rebuild and speedo calibration?

Tony