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Discussion Starter #1
Hi all,

66 coupe, 289 auto

I had the gauge cluster out to run a new switched power wire to my new tachometer, and now with it all back together the gauges are acting weird. When I turn the car on, the fuel and oil pressure gauges max out, and then slowly return to 0. The battery voltage gauge is normal, but my temp gauge is disconnected because I have an aftermarket one with actual degrees on it. I also noticed when I put my turn signal on, the signals work fine but the lights on the gauge cluster don't illuminate.

Prior to this all the gauges worked fine. I know for a fact I have gas in the tank and decent oil pressure. I've read that it can be the CVR mounted on the back of the cluster, can they just go bad like that? I took the cluster back off and don't see anything disconnected, no pinched or broken wires, and no missing grounds. I also double checked the nut on the back of the starter switch, it's still nice and tight. Any ideas?
 

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Grounds behind the cluster you mean? or just all the grounds?
the one at the cluster for sure and any other you may have bumped. Do not share the ground between any aftermarket gauges and the dash cluster, run a seperate wire and lug for that. Also check the main chassis ground between the back of the block and the firewall.

Many times after making a small change other issues show up as wires have been jiggled around.

Just so it helps diagnose this issue, all of your gauges are 100% hot at all times (after key on) the sending units including the gas oil and water temp all increase or decrease the ground potential as they change. It is this change in ground that moves the gauges. So a full tank of gas give's a different ground then an empty tank. this is done so that you don't have a "live or hot" wire in the tank or in the water jacket (which could cause increased electrolysis). Which is when negative ground systems US cars have a lot less problem than positive ground system (60's and 70's British cars anyone!)
 

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Agree with above. Bad grounds can cause all kinds of problems with you car. Here is the wiring diagram for your 66. Be sure you check the ground wire from the CVR (constant voltage Regulator) screw to the frame of the car which connects under the steering wheel shaft area. CVR -- wire (57 Black) -- to ground on frame. see jpg. You may want to clean this area with light sandpaper on the CVR and also on the instrument panel so as to make a good ground connection. Also, add "star" type washer and tighten screw may help.


http://averagejoerestoration.com/re...um-diagrams/1966-wiring-diagrams/66inter1.jpg

Hope you get things working right.
Not the average Joe ,but still Joe
Joe
 

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Discussion Starter #7
Checked all the grounds, no problems there. I have continuity between everything, including the grounds for the cluster. I'm leaning towards the CVR still. When I checked voltage on the IGN terminal with key on, I get 12.4 volts. It should drop to 5-6 volts on the output terminal but I get 0 volts. I know the signal on those switch rapidly but I checked with 2 different multimeters and got nothing. I ordered a new Scott Drake solid state one, so we'll see what happens.

I even tried cleaning up the terminals with sandpaper, making sure they were tight, etc. I disconnected the new tach gauge's ground and even the switched power wire and still same results.
 

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Checked all the grounds, no problems there. I have continuity between everything, including the grounds for the cluster. I'm leaning towards the CVR still. When I checked voltage on the IGN terminal with key on, I get 12.4 volts. It should drop to 5-6 volts on the output terminal but I get 0 volts. I know the signal on those switch rapidly but I checked with 2 different multimeters and got nothing. I ordered a new Scott Drake solid state one, so we'll see what happens.
Because the CVR 12V is a pulse averaging 5V, a digital volt meter doesn't work. An analog VM should give you a reading.
 

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Discussion Starter #9
I figured I would update this just for closure, gauges are all working again, it was the CVR after all. I replaced the stock one with a Scott Drake solid state updated one for like $45 from CJ Pony Parts. There are cheaper (~$20) versions, but from the reviews it seems none of them last long if they work at all. Money well spent in my opinion.

Thanks for all the help!
 
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