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Old 11-23-2005, 02:02 PM
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Ted_Z Ted_Z is offline
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Post $15 Ammeter/Voltmeter Retrofit write-up

As discussed in other threads, the stock ammeter in the factory gage cluster can be a fire hazard. As such itís recommended that you bypass it (move both wires connected to the ammeter to the same terminal).

Not having any information about your electrical system can leave you wanting. As such I'm presenting this voltmeter retrofit alternative that most shade-tree mechanics can do.

To start you'll need to remove your gage cluster from your dash. You also need to pick up a Sunpro Voltmeter (CP7985). This specific model voltmeter was chosen because the gage swings the same way as the stock ammeter. (Available at Autozone for ~$15).



Remove the 5 small machine screws from the back of the gage cluster (2 on top, 3 on bottom). You should now be able to remove the gage cluster from the housing assembly.



Remove the two small hex head machine screws (3/16") from the face of the oil/ammeter gage. Then remove the 2 nuts and lock washers from the back of the ammeter gage. Take out the ammeter and set it aside.



The voltmeter will need to be extracted from its original housing in order for it to be installed into the Jeep gage cluster. Carefully pry the trim ring off using a small screwdriver and/or pliers. Remove the two nuts and the paper washer from the back of the gage. Try not to loose any of the parts, as they'll be needed later!



With the voltmeter removed from its case, you'll quickly see how similar it is to the original ammeter in size and shape.



Wouldn't it be great if the voltmeter just dropped right into the original holes? Alas, no luck. While the hole spacing is about right, the new gage sits too high.

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Old 11-23-2005, 02:03 PM
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In order to get the new voltmeter in just the right spot, you will have to make new holes for the voltmeter's posts. This step is the most challenging portion of the retrofit. Take your time and remove a little bit of material at a time. Use the second picture below as a guide.

Remove the 2 nuts holding the oil gage. The oil gage, blue light cover and the support bracket will be free from the circuit board and the other gages. Set the oil gage and light cover aside.

2 of the tiny tabs on the bracket will need to be flattened. I used a round file to elongate the original holes, followed by a 5/16" and an 11/32" drill bit to provide a rounded cut. The bottom of the slot it just over 7/8" from the bottom flat edge of the steel bracket. The voltmeter's posts are also slightly closer together than the ammeters and the new holes are positioned as such. You want to remove enough material to that the plastic shoulder/spacer sits in the bracket like it did in the original voltmeter housing.



The holes in the circuit board will also need to be elongated. Use the bracket as a guide. The traces are just far enough away as not to be cut. These holes are not as critical as the ones in the steel bracket. Only the posts, not the plastic shoulder needs to fit through.



As you're cutting the slots, periodically check your progress by reassembling the oil and voltmeter gages into the cluster. Pay attention to the clearance between the two gages. The new gage will be in the perfect spot when the top of the voltmeter gage clears the housing of the oil gage by 1/16". Use the paper washer, brass nuts and washers to secure the voltmeter. The paper washer does a great job of covering up the elongated holes.



Here's the voltmeter in its new place with the gage cover in place. Donít forget to put the blue dash light cover in place before installing the oil and voltmeter gages for the last time (like I did).



And here is the final result. I cut the "volts" text from the voltmeter bezel and epoxied it over the "AMP" lettering. I also took the time to customize the two indicator lights. Since I have a Dana 20 in my Cherokee "Emergency drive" didn't seem to fit so I replaced it with "4X4". The unused spot got "Batt" to be used with the alternator. The old paint on the red lens was removed with a q-tip and some acetone. The new letters came from a label maker.



[ November 23, 2005, 09:19 PM: Message edited by: Ted_Z ]
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Old 11-23-2005, 02:15 PM
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daym....that looks really good!!! wish i had thought of that before i added some new gauges...
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Old 11-23-2005, 02:56 PM
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U BEECH
u beat me to it..i bought the exact gauge to retro the dash in my 75 4 days ago, that I already discoed the ammeter from...oh i hate you
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Old 11-23-2005, 03:01 PM
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ok now...tell us how you wired it.
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Old 11-23-2005, 03:03 PM
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Excellent post, and good info.
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Old 11-23-2005, 03:05 PM
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The two original wires that went to the ammeter go to the + of the voltmeter.

The - of the voltmeter goes to any ground.

Also install a wire from the output post of the alternator to the battery side of the starter solenoid. This reroutes the high current from the alternator directly to the battery.
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Old 11-23-2005, 04:49 PM
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You're just trying to make me feel bad that I couldn't figure that out myself and had to pay someone else to do it for me! What you've done looks very good. Great write-up
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Old 11-24-2005, 12:57 AM
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good looking work, one big ? do you think that is poossible to do with oil gauge? you know mechanical one. it would be nice to have both in the dash were i could see them.
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Old 11-24-2005, 02:06 AM
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Not sure what you're asking. You want to put a machinical oil gage in place of the stock electrical oil gage?
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Old 11-24-2005, 02:17 AM
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yes, a mech inplace of the stock one in the dash like the volt meter you are doing
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  #12  
Old 11-24-2005, 02:19 AM
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Wow! Now that is slick. Good Job!
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  #13  
Old 11-24-2005, 02:19 AM
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Also on your wireing of the volt meter, if you do it the way you say won't it read even with the key off? as it will come from the battery?
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  #14  
Old 11-24-2005, 02:39 AM
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Yes, the gage will read with the key off. The amount of current that the gage draws is about the same as the memory back up in your radio or the clock. Its a non issue. Plus if you didn't wire it this way you'd have to find a place to put the old ammeter wires is such a way that they wouldn't be at risk of shorting.

I have no idea if a mechanical gage will fit. Please post your findings if you try it.
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Old 11-24-2005, 03:23 AM
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I am impresssed. Thank you for this excellent write up.
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  #16  
Old 11-24-2005, 05:22 AM
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Quote:
Originally posted by steven79:
Also on your wireing of the volt meter, if you do it the way you say won't it read even with the key off? as it will come from the battery?
well what you can do is to connect the 2 OE wires from the back of the ammeter together away from the new voltmeter, and then cover with shrink tube. then connect the + of the voltmeter to a switched source.

but tedz way is simpler
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Old 11-25-2005, 10:15 AM
Joe Guilbeau Joe Guilbeau is offline
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This is not a bad idea, however as mentioned on other posts on this subject matter, it is not nearly critical as some might have you believe.

The reason that this is so is because the Alternator's output is generally sent to the Ammeters Positive post AND to the big splice (generally Wire #12) which also feeds the following:

1. The Fuse Box
2. The Ignition Switch
3. Light Switch/Dome Light
4. Horn

So, this means that the Ammeter is only passing the current that the Battery needs in order to be charged, which is controlled by the Alternator's Regulator.

What IS true, is that if there is a short to ground in the Ammeter circuit then there will be a major problem.

In reality, if the regulator circuit is in good shape and you simply run an ANL fuse inline on the Alternator Output and the return charge line going to the Positive Terminal of the Solenoid you will be perfectly safe.

The ammeter only displays the charge rate of the battery, this is why in normal good running jeeps the alternator reads almost "Zeo" amps.

This is because under normal operating conditions, the battery is recieving just a trickle charge, as the alternator is supplying most of what the vehicle needs in order to run thru the splice and not thru the Ammeter.

When the vehicle just starts up, the ammeter reads a negative charge rate because the battery is supplying amps to the starter (like 200 - 400 amps).

This is why the ammeter initially goes negative, because of the Positive/Negative terminal hook-up of the ammeter in the circuit, The battery is giving up amps, and this dep;etion flow rate is indicated on the ammeter, after the vehicle starts the alternator sez... "...Gee let's give that ole battery some juice...", cause it appears to be somewhat low.

So now the ammeter shows a positive charge for a few moments so the battery can take up the charge that the starter has just depleted.

With a good battery and alternator combo, and a good starter, the charge rate to replenish the alternator should not take but a minute... any longer than this indicates that the battery does not have enough reserve capacity to supply the starting current and voltage that the starter needs, and puts too much of its capacity into the starting process.

Then the ammeter shows a large current transfer to the battery as the alternator attempts to replace the depleted charge.

[ November 25, 2005, 05:23 PM: Message edited by: Joe Guilbeau ]
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  #18  
Old 11-27-2005, 05:03 PM
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I am completely at a loss for words in the quality of the work you did, and if copying someones work is really a form of flattery, then consider yourself flattered. I'm in the area, so if you can point me to a source for the Voltmeter, and save me a little legwork, I'd really appreciate it.
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Old 11-28-2005, 01:04 AM
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I picked the volt meter up at my local Autozone.

You could also get it online from them. Just do a part number search on www.autozone.com for CP7985.
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Old 11-28-2005, 12:40 PM
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Ted_Z,

Thanks for the follow up reply, and sorry for missing it in the original writeup. I was too busy looking at the pictures. Anyways, it's an awsome mod, and so well done it's pretty much invisible to anyone who doesn't know better.
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