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Author
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Topic: Why Dont My Gauges Work?
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69 Sportsroof
Gearhead Posts: 2064
From: Valley, Alabama, USA
Registered: Mar 2002
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posted 08-21-2005 01:53 PM
   
I know this is getting old for you guys cause it's certainly getting old for me but my guages dont work. They were working before I had the paint job done but now they dont. I've cleaned the mounting tabs and screws. I've even sanded the back of the cluster where the ground screw goes. I just finished replacing the voltage regulator with the new unit NPD offers and they still dont work. What gives? What am I missing? The lights work so I dont think it's a problem with the new printed circuit. Any help will be greatly appreciated.
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Fastymz
Moderator Posts: 20129
From: Reno Nv USA MEM#1240
Registered: Apr 2001
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posted 08-21-2005 02:32 PM
Did you replace this unit?http://www.mustangsplus.com/Merchant2/merchant.mv?Screen=PROD&Store_Code=MPFMP&Product_Code=00152&Category_Code=Voltage_Regs ------------------
oddly obsessed with big scoops on little Mustangs 65 coupe 351w C4 Big Boss 429 hood scoop,8" 3.40 TracLoc. My Pics
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69 Sportsroof
Gearhead Posts: 2064
From: Valley, Alabama, USA
Registered: Mar 2002
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posted 08-21-2005 03:12 PM
quote:
Originally posted by Fastymz:
Did you replace this unit?
Yep. That's the part I was refering to from NPD. They have a new transistorized unit out that maintains a steady voltage instead of pulses. I'm in the process of going through the grounds now - again.
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Fastymz
Moderator Posts: 20129
From: Reno Nv USA MEM#1240
Registered: Apr 2001
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posted 08-21-2005 03:18 PM
Have you checked for power going to the gauges?------------------
oddly obsessed with big scoops on little Mustangs 65 coupe 351w C4 Big Boss 429 hood scoop,8" 3.40 TracLoc. My Pics
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DidgeyTrucker
Gearhead Posts: 1423
From: Greenbrier, TN USA
Registered: Oct 99
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posted 08-21-2005 07:51 PM
Are you getting voltage going TO the voltage regulator? Did you yank on the wiring harness around the ignition switch? Sounds like a problem between the switch and the regulator. The gauges are grounded through the sending units.Tracy
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69 Sportsroof
Gearhead Posts: 2064
From: Valley, Alabama, USA
Registered: Mar 2002
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posted 08-21-2005 10:18 PM
quote:
Originally posted by Fastymz:
Have you checked for power going to the gauges?
Well, I have power going to the dash lights. I'm using a wiring diagram from a Haynes manual and it shows only one power feed to the instrument cluster. I did find a broken ground wire that went from the alternator to the main voltage regulator mounting screw and that's fixed now but still no go on the gauges.
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DidgeyTrucker
Gearhead Posts: 1423
From: Greenbrier, TN USA
Registered: Oct 99
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posted 08-21-2005 11:06 PM
The power to the dash lights is a totally different feed than power for the gauges.Tracy
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Toronado3800
Gearhead Posts: 986
From: St. Louis, MO
Registered: Jul 2001
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posted 08-22-2005 12:38 AM
I found myself unable to follow the instructions, but with some of the aftermarket gauges I purchased they said I could not use teflon tape to seal the threads because the tape would keep the sending units from grounding.In my car the tape is necessary to keep the sending units from leaking adn they do ground, but maybe, just maybe. I wonder if you can test the ground of your sending units with alligator clips... or by attaching the ground end of a test light to a sending unit and then to the positive battery cable (if that won't fry something)
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69 Sportsroof
Gearhead Posts: 2064
From: Valley, Alabama, USA
Registered: Mar 2002
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posted 08-22-2005 09:12 AM
quote:
Originally posted by DidgeyTrucker:
The power to the dash lights is a totally different feed than power for the gauges.Tracy
Thanks Tracy (and Scoop!). That may be the problem. The power feed I'm talking about connects to the battery side of the solenoid. Is this the power to the guages? I'm going to guess that the lights get their power from the headlight feed?
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69 Sportsroof
Gearhead Posts: 2064
From: Valley, Alabama, USA
Registered: Mar 2002
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posted 08-23-2005 02:00 PM
I had quite a bit of overspray on my solenoid terminal so I replaced it hoping for more positive results. Even put a new end on the wire going to the headlight harness. Still no gauges working. Tracy had mentioned something about the ignition switch. The only thing we did to it was to install a new cylinder. Could that be the culprit? The cylinder doesn't make any electrical contacts but what else could it be? This is really starting to get under my skin.
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Clark
Gearhead Posts: 716
From: Rowlett,Texas
Registered: Aug 99
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posted 08-23-2005 02:55 PM
That ignition switch cylinder can be the problem because the gauges on mine do not work until the key is turned, so it has to be feeding power to the gauge cluster.You also mentioned the headlight wiring at the solenoid make sure it is on the battery side post. Remember to go back through what has been done since the last time they worked and eliminate those first. ------------------
69 393W Sportsroof Deluxe
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shoe
Gearhead Posts: 253
From: midwest
Registered: Feb 2001
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posted 08-23-2005 05:27 PM
I had this problem after restoring my complete 69 car last winter. Here is what after 200 plus hours & every combination of problems were addressed. It stumped 2 different mechanics One an electrical expert.
Ford had problems with the printed circuit panel actually groungind out the guages because the holes thru the plastic circuit panel were too small & if one of the two terminals touches the copper in the printed circuit bingo no guages. I tried repro new circuit panels 12 plus & new constant voltage regulators & 3 or 4 different panels with every combination of different quages from these panels into mine and it still did NOT work till I enlarged the holes and was VERY carefull when spinning on the sheet metal style nuts onto each guage. That was the problem. I talked to several folks at shows & swap meets who had the same problem & this was the solution for them also Hope this helps, Shoe
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69 Sportsroof
Gearhead Posts: 2064
From: Valley, Alabama, USA
Registered: Mar 2002
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posted 08-23-2005 07:21 PM
quote:
Originally posted by shoe:
if one of the two terminals touches the copper in the printed circuit bingo no guages...I enlarged the holes and was VERY carefull when spinning on the sheet metal style nuts onto each guage.
Ok. Now I really am confused. If the copper doesn't contact the terminals, how are they going to work? My printed circuit has plastic that goes past the copper so it prevents them from touching. The nut is what's creating the continuity from the copper in the printed circuit to the terminals (posts) on the gauges. The only thing along those lines that I can see being the problem is if I have the washers in the correct place. Do they go between the printed ciucuit and the cluster or between the printed circuit and the nuts?
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DidgeyTrucker
Gearhead Posts: 1423
From: Greenbrier, TN USA
Registered: Oct 99
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posted 08-23-2005 08:06 PM
OK. You need a voltmeter and some wire. It sounds like you have the cluster out of the car. I don't have a '69 so I don't know the specifics. But I know how gauges work. This applies to fuel, water temp and oil pressure gauges - NOT amp gauges.To check the sending unit:
If the harness is all hooked up, turn on the key and take the wire off the sending unit and touch it to ground. You might have to stick a small screwdriver or wire up into the connector. This should make your gauge go to a full reading. To check the cluster:
Turn on the key and make sure you have 12 volts on one side of the regulator. There should be less on the other side. On one terminal for each gauge you should have this same voltage. If you do, take some wire and connect one end to a good metal ground. Touch the other end to the terminal on the gauge that did not have voltage. This should make your gauge go to a full reading. I'm not sure what washers you're talking about since I've never worked on a '69. Most of the metal on the backside of the cluster will be ground. The printed circuit will be hot or connections to sending units, which need to isolated from ground. If the washers are plastic they are insulating washers and need to be between any metal and the printed circuit. Hope this helps and doesn't confuse. Tracy
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buening
Journeyman Posts: 56
From: Decatur, IL
Registered: Mar 2005
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posted 08-24-2005 01:04 PM
quote:
Originally posted by 69 Sportsroof:
Ok. Now I really am confused. If the copper doesn't contact the terminals, how are they going to work? My printed circuit has plastic that goes past the copper so it prevents them from touching. The nut is what's creating the continuity from the copper in the printed circuit to the terminals (posts) on the gauges. The only thing along those lines that I can see being the problem is if I have the washers in the correct place. Do they go between the printed ciucuit and the cluster or between the printed circuit and the nuts?
In 69 clusters, there was a nut and washer that held the circuit board to the guage post. In 70, they went to a nut with integral washer or basically a one-piece design. Make sure that you have the little gray felt material between the circuit board and the metal housing. This felt material should be rectangular and has two holes, each for the guage post. These felt things slide over the guage posts (one felt per guage) and should fit snug. It will hold the guage in place until you get the printed circuit and nut attached. You also need to make sure that the guages are aligned properly in the metal carrier. Look at the carrier and look at the guages and you'll see what i mean. There are tabs that have to be aligned. Once the guages are aligned, the felt thing slid onto the posts holding the guage in place, then the printed circuit, and then the washer and nut. Also note that there are two grounding bolts. One that attaches the constant voltage regulator to the housing and another at the top right of the center housing when looking at the cluster/printed circuit (or left if looking at the guages when the dash is installed). These provide ground for the printed circuit, but the metal housing needs to be grounded also. This ground comes from the upper two attaching screws that mount the center housing to the lower windshield brace. Either you are not getting any juice to the cluster, the guages are grounding themselves out, or there is no ground. Hope this clarifies some. Also, this power wire to the battery terminal of the solenoid provide power to pretty much everything on the car. If you have dash lights then this wire is doing its job.
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1970 Grabber Blue Mach 1 H-code
1970 Fastback
2003 Torch Red Mustang
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69 Sportsroof
Gearhead Posts: 2064
From: Valley, Alabama, USA
Registered: Mar 2002
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posted 08-28-2005 06:44 PM
With my trusty volt meter I checked for voltage at the plug on the wiring harness. I'm getting 11.89 volts going to the dash with the key 'on' and 13 volts with the engine running. That sounds about perfect. With the cluster plugged in I'm only getting 2.8 volts on the high side of the new solid state vr and nothing on the low side. When I check the resistance on the printed circuit I get .3 ohms from the contact point to the high side of the vr. Any ideas why I'm losing 9 volts between the plug and the vr?
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