[Aaron65]

Over this past year, I've noticed that my temp gauge and my oil pressure gauge (on my '74) are reading slightly higher than they used to. For example, hot idle oil pressure reads closer to 30 psi than 20, and the temp is about one tick closer to the 210 mark.

I know a lot of cars have an IVR to limit gauge input to 5 volts or so, but I couldn't find one in a parts search for the Firebird. Thanks for any input!

[steve25]

The only voltage regulator I am aware of is in the Alternator.

I would question how good your ground connection is at the battery or how good that overall cable is.

A high resistance thru the circuit might cause the regulator in the Alt to pump out more voltage , also I guess your battery might be going south.

[Aaron65]

Originally Posted by steve25

The only voltage regulator I am aware of is in the Alternator.

I would question how good your ground connection is at the battery or how good that overall cable is.

A high resistance thru the circuit might cause the regulator in the Alt to pump out more voltage , also I guess your battery might be going south.

I actually just replaced the alternator because it was overcharging and the battery load tested OK (it's only three years old). I also have replaced the battery cables over the last couple years. I guess I'll have to keep an eye on it...thanks!

[steve25]

On the rear of one if not both heads is a braided ground strap that brings ground to the fire wall from the motor, and your instrument cluster main ground goes to the firewall as well.

I would also check both of those.

[Aaron65]

I don't think I've checked the instrument panel ground, so I'll do that. I did a "voltage drop" test on the block to subframe grounds a couple years ago and they were good, but they're worth another look, too. Thank you!

[78w72]

Braided ground strap is on the passenger side head to firewall.

The instrument cluster ground is just a little metal strap from the headlight switch to the instrument cluster housing mounting bolt, since the dash on 2nd gens is plastic where the cluster mounts it needs that ground strap to ground it... but I have had & seen clusters without the strap that still work ok for whatever reason. Verify the head & firewall dont have any paint where the ground strap mounts too.

Usually a bad or compromised ground will cause the gauges to read lower since they arent getting a full connection as opposed to reading higher. If you haven't done it, try confirming the oil/temp readings with a known good mechanical gauge, maybe you have thicker oil than previously used causing a higher oil psi reading?

[track73]

Interessting..I have mechanical guage in the engine compartment and it reads higher that the instrument panel guage and the temp guage on the IP reads higher than my infrared temp gun.

[Aaron65]

My infrared temp gun reads about 185-190 at idle, but it does rise at freeway speeds a bit, so it will be tough to measure. Looking at the gauge, I'd say it is in the 200* area on the highway, which isn't a problem, but like I said, it's a tick higher than it was last year.

I always use 10W30 Rotella and I don't change filter brands usually. I actually didn't change the oil this year - I usually change the oil every two years, because the cars generally get 1000 miles a year each on them or so.

[Aaron65]

My infrared temp gun reads about 185-190 at idle, but it does rise at freeway speeds a bit, so it will be tough to measure. Looking at the gauge, I'd say it is in the 200* area on the highway, which isn't a problem, but like I said, it's a tick higher than it was last year.

I always use 10W30 Rotella and I don't change filter brands usually. I actually didn't change the oil this year - I usually change the oil every two years, because the cars generally get 1000 miles a year each on them or so.

[Formulas]

There is a flat white resistor bar on the back of these stock gauges they are color coded red, blue, green, and perhaps another color but never seen one changing / swapping those will give you a slightly different reading, perhaps to match the real engine readings if your sure which way to go

IE you have a mechanical reading of 160 water and you use a IR gun on your engine and it shows close to 160 but your dash is 200 change out one of these bars and adjust the dash down to reality

and probably a regular electronics resistor would suffice if you get the right value but I've never tried that

.

[78w72]

Originally Posted by Formulas

There is a flat white resistor bar on the back of these stock gauges they are color coded red, blue, green, and perhaps another color but never seen one changing / swapping those will give you a slightly different reading, perhaps to match the real engine readings if your sure which way to go

IE you have a mechanical reading of 160 water and you use a IR gun on your engine and it shows close to 160 but your dash is 200 change out one of these bars and adjust the dash down to reality

and probably a regular electronics resistor would suffice if you get the right value but I've never tried that

.

What or where is this flat white resistor bar on the back of 2nd gen firebird gauges? Unless its hidden somewhere out of sight, Ive never noticed anything like that on the numerous 2nd gen gauges Ive had, have taken them apart many times and even have 2 clusters sitting on my counter and dont see any resistor bars like that on them. Just curious if all mine are missing something or Im not seeing it?

[Held for Ransom]

Originally Posted by 78w72

What or where is this flat white resistor bar on the back of 2nd gen firebird gauges? Unless its hidden somewhere out of sight, Ive never noticed anything like that on the numerous 2nd gen gauges Ive had, have taken them apart many times and even have 2 clusters sitting on my counter and dont see any resistor bars like that on them. Just curious if all mine are missing something or Im not seeing it?

My last post...
https://forums.maxperformanceinc.com...d.php?t=806789

[78w72]

Originally Posted by Held for Ransom

My last post...
https://forums.maxperformanceinc.com...d.php?t=806789

That looks like the fuel/volt gauge?? The OP here is talking about temp/oil psi issues with the gauges in the main cluster... the last post was saying the clusters have a resistor that would effect the temp/oil readings.

[Held for Ransom]

Originally Posted by 78w72

That looks like the fuel/volt gauge?? The OP here is talking about temp/oil psi issues with the gauges in the main cluster... the last post was saying the clusters have a resistor that would effect the temp/oil readings.

That's what I get for just skimming the thread. As far as I know, there is no shunts in the cluster gauges.

[Formulas]

this is the back of volts and fuel i dont have the main cluster avail to look at

[78w72]

Originally Posted by Formulas

this is the back of volts and fuel i dont have the main cluster avail to look at

The issue is with the oil/temp gauge in the main cluster, a resistor on the fuel/volt gauge is unrelated to the main cluster readings.

Main clusters dont have any resistors or voltage regulators.

[Formulas]

Ok so none originally at that spot

pretty sure those circuits could be altered in the same manner but i digress