[jethrocf]

I just started my resto with all new everything. The amp gauge is reading -20 to -30 while running. When not running, but key on, it reads 0. What gives? My experience with these gauges is that you get little fluctuation ever, unless something is wrong. It's a 70 with gauges, big block, M&H wiring throughout.

Thanks,

Jeff

 

[Steve S]

-20 -30 is a lot of discharge. Do you have any problem with battery discharge.
If not I suspect the wires to the amp gauge are reversed. Either in the under dash harness or the engine harness.

 

[jethrocf]

Thanks Steve, I just fired up for the first time ever. So I don't know how anything reacts. Do I have a problem with battery discharge? I don't know. What I do know is this from yesterdays post: " I have a 70 with all new M&H wiring. I put power to it yesterday for the first time. I seem to have a hot wire (brown) going in to the regulator with the key in the off position. Shouldn't this be hot only with key in on position? I wasn't ready to start it yet, just checking to see if stuff worked. All new gauge dash harness, forward lamp, and engine. New reg., Alt., the works. Everything else worked; clock, lights, flashers, except the front right did not flash. Haven't checked the bulb yet. Where do I start looking? I have the ignition switch from the Malibu dash, should I try there first?"

Then my next post: I swapped ignition switches with the old one just to find out it apparently mounts differently as the start position is in the lock spot, er, uh, you know what I mean. Anyway, just jacking with wires under there I seem to have fixed the problem of a hot brown. I have a hot orange, but I think thats normal. Turn signal is flashing too!

So something under there could be amiss, but where do I start?

 

[wayner66]

With the key on so that the amp gauge is on but with the engine off, start turning things on, heater blower, parking lights, then headlights, cig lighter, horn. You should see an increasing discharge with each thing turned on if the wiring is correct. If you see an increasing charge, then the wires are reversed on the gauge. Check the condition of the battery. If it is very low and or near dead, then your battery is fully charging with the engine running and a reversed amp hookup would explain what you have described.

 

[Elree Colby]

 

[jethrocf]

Doesn't the amp gauge work off of the circuit board? Meaning there aren't any wires directly connected to the gauge. If so, how could they be reversed?

 

[jethrocf]

All wiring is brand new M&H for the correct application. Alt output is wired to reg as original harness would be. Battery is new, as is alt, reg. and all other parts on car.

 

[jethrocf]

Wayne, you are on to something! I just ran your test, and with each accessory I turned on I got a larger +reading. Now, how do I fix it???

Thanks

 

[wayner66]

Jeff, It sounds like everything is working normally except the amp gauge because there are no other odd electrical symptoms, correct?

Well, the simple answer is to reverse the wires on the amp gauge. I don't know how to do that off the top of my head.

I am fairly well familiar with the electrical system of my 66, and it's operation is similar to all Chevelles, but I don't know much about the details of your 70 harness, such as where the connectors are located. Could two wires be reversed in the connector to the circuit board? I am going to dig around here on TC as I recall a diagram of the amp gauge and charging circuit. I will be back.

 

[wayner66]

Jeff, Do a search for the following phrase (use the search titles only) "69 idiot lights to gauges amp meter." The thread is long, but it is full of info you should find helpful. One of the posts in the thread has a diagram of the charging circuit and the amp gauge.

I think the next step is to find out where the wires to the amp gauge are crossed.

 

[wayner66]

Jeff, I need to sign off for the night, but hate leave you hanging. I would suggest that before ripping into the harness, you might give M&H a call and let them know what you have observed. If their tech support is any good, you might find a solution quite fast through them. Wayne

 

[Steve S]

If it is an aftermarket amp gauge I believe I have seen others post the same problem. The wiring may be correct for the OEM amp gauge but be backwards for the aftermarket gauge. You have three choices to correct the problem, pick the one easiest for you to get to. The gauge connector, reverse wires 3 & 4 OR The bulkhead connector - reverse wires in pins DT & DS OR Engine Harness, reverse wires DT & DS.

 

[1Fast7D]

There was also some replacement PCB boards that were made incorrectly and cause the amp gauge to read backwards. See post here http://www.chevelles.com/forums/showthread.php?t=94825

Reversing the wires Steve S explained will also make the gauge read correctly.

 

[jethrocf]

Thanks to everybody for the info, especially the links to previous posts on the same subject. I talked to M&H tech support, he said he gets this call twice a week. Apparently the gauge is aftermarket, or if not, the PCB is, and one of the two are wired backwards. He said he has talked to the manufacturers and they don't much care that their product is wired wrong. One company sends out a sheet with instructions on how to swap wires at PCB connector to fix problem. Anyway you look at it, it's a PITA. But at least I know my harnesses aren't about to melt!

Thanks, Jeff