I purchased a VDO 2" ammeter (30A) and 2" VDO voltmeter from NAPA to install on my 1958 3600, 235 powered NAPCO. The ammeter in the dash gauge assembly works, I wish to have additional gauges. I have searched for details for the best way to install and not found what I think I need. The VDO ammeter does not indicate that it is a gauge that needs a shunt wire. No details about this on the gauge to find out this detail. Does anyone have a simple schematic to install this gauge in a safe and effective manner that will show when the system is charging? I would also greatly value a simple schematic for the voltmeter install. I am also looking for suggestions from the forum for the best tachometer that will connect to the original ignition 235, 6 cylinder.
I figured this would happen. I search like a madman and find nothing. The day after I post an appeal for help, I find exactly what I need from the VDO website. Embarassing; yes. I scanned in the schematics for both meters. The VDO ammeter does NOT require a shunt wire for correct operation
OK, maybe the electrical gurus will correct me. That ammeter schematic looks wrong. If wired that way it would show any power through the fuse box to display in the ammeter as a charge amount. This would be misleading and you really don't want all your loads from the fuse panel to go through the ammeter, only the amps value that is actually charging or discharging the battery. Am I missing something?
Two ammeters? OK, just wire the new one in series with the old one. To do that, just identify the battery wire from the starter to the existing ammeter. Cut this wire and wire the ends to the new ammeter.
I looked at your post in the gallery and see that you have installed an alternator. I'm not sure what happens to a 30A ammeter if more than 30 amps flows through it. Maybe it just pegs at 30A without damage or maybe it blows like a fuse.
Re the schematic. I agree that the back light and fuse should be wired to the same side of the gauge as the ignition.
I found these schematics after a call to the VDO customer service site. I figure its still a GREAT idea to ask questions before install to use others experiences to an advantage. Does anyone have an idea about ammeter capacity (30, 60?) of the stock, in dash,gauge cluster Task Force Series trucks? The stock unit shows charge (maybe 1/4" past zero amps mark) after first start of truck until charge is satisfied. The idea of the second ammeter is to see what this system puts out for amps, as well as voltmeter for charging system performance. This preference of ammeter vs voltmeter was covered in other previous posts.
Mine is a 59, 3200 originally a 235 converted to a 350. My alternator is the basic 10SI capable of about 55-60 amps max. I don't know the spec capacity of the stock ammeter, but mine has functioned well without any 'shunt' for the 6 years or so and thousands of miles that I have been driving it. If the battery is slightly discharged the meter pegs at first when I start the truck, I just let it idle a few seconds until the meter starts to drop back as the battery begins to be charged. Others may have had problems using the stock ammeter, this is my experience.
There is definitely a problem with that schematic VDO provided. The fuse box should be connected to the same side of the ammeter as the alternator if you intend it to indicate charging and discharging amps. The only things that might be connected directly to the battery are high current items seldom used like power seats, trailer brakes controller, or horn, not the light switch or fuse box. If you really intend to actually read the alternator output in amps (not charging amps) just wire the new ammeter in series into the main power wire coming off the alternator.
Not sure you understand ammeter wiring or not. This is just my answer to the post.
1. One side of the ammeter gets battery voltage direct from the battery. 2. The other side gets ALL the loads to read. ALL loads includes the alternator, the fuse panel, ignition switch. The ignition turns on some of the fuses. Other fuses are always hot. Ammeter reads all fused loads. 3. The "Light Switch" you see in the diagram is simply the headlight switch which, as you know, has a gauge light terminal on it for turning on gauge lights/panel lights as one of the functions of the headlight switch. One of those lights is inside the ammeter to illuminate it. They are just showing how to wire the light. They are NOT showing the fuse box attached to the wrong side of the ammeter. The battery is providing power to the starter and chain wired to the ammeter. The battery is also feeding the fuse panel buss bar. 4. The VDO ammeter shunt design does not matter to you. What matters is what the spec of the ammeter says about AMP capacity. Your amps on a 59 truck will not exceed a modern VDO ammeter. If you had a 130 A alternator on a 59 truck with stock accessories, The alternator would never produce 130A because it only produces the necessary demand. (voltage regulator) 5. Be sure your alternator and battery feed wires are big per normal convention. 8ga/10ga 6. That's all there is to this. 7. Very nice rare truck!
Unsolicited advice: You are going WAY overboard. All you need is a voltmeter. An ammeter is NOT necessary. It has multi hot wires on one terminal. All the hot load wires. Your 59 could have had as high as a 50 A generator. The generator may have had a 10%-15% reserve capacity. The original ammeter could read that if necessary.
A voltmeter has one small 12V wire from the ignition switch to one terminal and a ground wire to the other. Simple. All you want to know it is your battery condition/charge rate. A secondary idiot light is a good visual warning indicator. Maybe you have discussed the Ammeter vs Voltmeter. The experts say Voltmeter. GM dropped the ammeter in favor of volt gauges and idiot lights. You are adding gauges like you are monitoring a manned moon shot. It's just a 59 truck. The alternator will last a long time. You will know something is wrong if the idiot light comes on and voltmeter shows discharge at higher than idle. Don't worry so much.
I can't get into the VDO website without saying OK to "cookies" so don't know if the diagrams are legit but they are poorly done, look old fashioned and the nomenclature is very, very unprofessional for an electronics company. I do see that diagram shown on several third party blog sites. I never trust those.
