No luck with the guages

[ETstang 10]

Well - it's going on 3 months and no solution to the inoperable gauges - Temp, Oil & Fuel.

I have gone through the whole explanation and testing from the http://1970mgr.org site.

I have a new PC board (film)

I have replaced the CVR with a DC/DC Converter for 5 volts (the tachman didn't work).

I have checked continuity on all the gauges - and none are Grounded.

I do have proper continuity from the PC board connection point (where the cluster connector plugs in) all the way through the converter to the gauges.

I do have proper continuity from the PC board connection point (where the cluster connector plugs in) from each gauge sending unit to each of the gauge posts.

Using an external power supply, when I apply 4.5 volts to each gauge, I get the gauge to move properly - as if the sending unit was sending the current.

In other words, on the bench it all looks and act like it is supposed to.

So I go the cluster connector and check for voltage on Pin #11 - the one that feeds the CVR - turn on the ignition and I get 12 volts.

 

I plug it all in - screw it down for grounds and turn on the ignition -

No gauge activity

 

I really would prefer to stay stock with the car - it is one of a kind - but????

 

Do I throw 'em all out and go for direct mechanical gauges

 

Solutions Guys, PLEASE

Thx

Dick

[69RavenConv 286]

Wow, good one (or bad one for you, actually). IN theory, it works like this; the car supplies 12V, the CVR (or converter) knocks it down to 5V. The 5V flows thru the gauge, thru the harness, thru the sender, and finally to ground (chassis). The senders are just variable resistance devices the affect the flow of current. The amount of current flowing affects how far the gauge deflects. As long a s the flow is there, you should get results.

 

So, a couple of thoughts. Are you sure the 12V is getting to the PC board? You say it measures good in the connector, but maybe the connector is not making when you plug it in?

 

Is the converter you installed capable of supplying ~2 amps of current? These old gauges are brute force and take a lot of juice. All modern converters limit the current when overloaded, usually by dropping the output voltage (thus dropping the output current too). If the overload level of your converter is rated too low, it will cut out and fold back under (what should be) normal operation.

 

Hmm, this is a long long shot but do you have a good ground at all the senders? Engine block and chassis (fuel tank) connected to battery ground?

 

Finally, have you tried disconnecting all senders but one (one at a time)? Maybe you have one bad sender circuit that's collapsing the power to all 3? Look for a short in a wire to one of the senders. This would kill the 5V and kill all 3 gauges with it.

 

As a last resort, maybe pick up a new cluster at a swap meet? If it works, the cluster/converter was the problem; if it still fails, its a bad wire or sender.

 

Keep us posted, there are others who have electrical problems out there.

[LoneWolf2U 136]

screw it down for grounds ?

 

There is a grounding wire that comes from the pigtail plugin off the panel.

it should be near the main wire loom at the dash brace using a small selftapping screw.

Without this ground attached the panel will not operate guages or lights correctly.

[flight96 14]

I had the same issue. It took me a while to get them working. What I did was....

1. I replaced all the little 'cardboard' backings on the guage posts with rubber pieces. That way they wont breakdown over time.
   
2. I cleaned all the leads from the wire harness that plugs into the cluster circut board. I found that there was a few contacts that were corroded and a few were bent.
   
3. I replaced the engine guage wire harness. This is the one that goes from the firewall to the guages and coil. The old one had cracks in it. Its a cheap and easy replacement.
   

Good luck, I know its a very frustrating thing dealing with electrical. I still have a few small issues with lights......

 

 

 

B&DIMH

[danno 128]

I can understand the frustration, but there is always an explanation. You have some good suggestions already, but I would suggest a couple more ideas. Temporarily connect 3 wires to the voltage regulator you have on the back of the PC board (film). One of the wires should be under the screw where it connects to the housing, this is a ground wire. The other 2 wires should connect to the spring clips on it that are like those on a 9 volt battery.

 

Then install the assembly in your car, turn on the ignition, and measure the voltage on the 2 wires connected to the spring clips. Use the wire connected under the screw as the - input to your voltmeter. You should get +12 volts on one of the wires and the other should be 5 volts for an average. I say 5 volts as an average because it will go up and down in voltage.

 

If you do not get the 5 volts on the output, start by disconnecting the leads going to the temperature and oil sending units. You can do this by unplugging the 3 lead connector under the hood that connects the interior wires to the engine wires. The 3 pin connector is in back of the carb, by where the accelerator cable comes out of the firewall.

 

If you disconnect this and you still do not have +5 volts, you either have a short on the +5 volt line or the voltage regulator is not working. I have heard some of the aftermarket regulators are junk. The OEM products were very robust, a good design.

 

The suggestion from Flight96 about the cardboards under the guage posts is very likely where the problem could be, check that.

 

Good luck, stick with it, and resist the temptation to buy all new gauges.

Danno

[Mike65 475]

Check to make sure the gauge posts are not grounding out on the cluster body, I have heard several instances from some of the guys on www.Vintage-Mustang.com about this.

[ETstang 10]

Got my work cut out for me - really great responses - thank you all.

Couple of points - the gauges are fine and not grounding (although I like "flight 96"'s idea of the rubber mounts) - I can apply current to each one and get the needle to move appropriately. The whole dash assembly does get grounded when it is installed - it uses the mounting screws to be sure there is a good ground to the metal dash framework. And my Dc/Dc converter is properly providing 5 volts to each gauge.

 

This is leading me more and more to the cluster connector that "plugs-in" to the back of the flexible pc circuit board. Gonna try a temp. wire-around to see if that might be it.

 

Thanks again guys - that's part of what makes this Forum really great and fun.

Dick :-)

[danno 128]

Did you test the 5 volt supply with it hooked up in the car and when the gauges are not working? I still think that is the problem, it is the only common item between the 3 gauges that could cause this.

Dan

[jimmystang 13]

Mines a 70 non tach car. The diagrams getting around on the net are 70 tach so the colours are different.

The earth is good if your dash lights work. That is all the earth does, it has nothing to do with the gauges. Make sure the dimmer is turned up to see the lights.

The gauges all earth at their senders. Obviously not the amp meter.

Follow the sender wires in the engine bay and with the ignition on test the wires with a test light. It will flash with the VR working. If you have no power it sounds like a fault at the main PCB plug. Hook the plug up and check with a test light at the posts on each gauge. It sounds like a common supply problem with all 3 not working.

[MAD IN NC 21]

First - I fought the very same problems as flight 96, the cardboard insulators and gauges grounding. If you search on this site you will find a posting and link on how to center and check the gauges.

 

Second - I found out the PC Board/ film was bad with small fracture cracks that would appear/ disappear when touching it. New board Mustang Unlimited for ~$50 fix it.....

[buening 63]

Plug the connector into the back of the gauge cluster and but do not screw the cluster to the dash. Take your multimeter and verify the 12V wire has voltage. Follow that lead wire around the printed circuit and spot check each terminal.

[Boogerschnot 12]

I know it was said before but you do need to ground the PCB using a wire to a screw at the middle of the pcb. And isnt the housing made of plastic or pot metal? so how would it ground to the dash using mounting screws?

 

When I rewired my dash I traced every line in the PCB to be sure that the connector was pinned correctly. The book I had was wrong in reguards to what pin did what.

 

And are you positive that you have the correct PCB for your application or wiring diagram that you are using. It may be wrong, in other words, you may thing that you are plugging it in to the corresponding sensor but you are not. and make sure your connector isnt upside down as you plug it into the board.

 

It doesnt sound like the board/guages are the problem. unless they are not matched up correctly between the male and female plug.

[buening 63]

The CVR is grounded to the metal gauge housing as well as there is a ground screw in the upper corner of the center metal gauge housing. When you bolt the cluster to the dash, screws go through the center metal gauge housing providing a ground path to travel from the metal dash.

 

I seem to remember something about a change from 69 to 70 and there being a difference in harness grounding but it's been too long ago. Maybe others can clarify.