Fuel and Temp guages not working

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   I think this is my first post, so be gentle with me guys...err...gals 
I have a 68 Javelin that I'm messing with. I had the instrument cluster out to replace some lights. I also had some alternator issues I was dealing with. I've got those sorted out but now my Fuel and Temp gauges don't work. Looking at the wiring diagram I see they are both fed by the same CVR, so I replaced it.  That didn't fix the problem, so I pulled both of them out and tried to test them using a bench-top power supply. I get nothing. Maybe I'm testing it incorrectly, but that's what I need advice on. I saw an earlier post on this subject and, sure enough I've got the old bi-metal gauges with what look like very delicate windings on them.

My question are: 
1:  Is there a sure fire way to test these gauges to determine weather they're bad? I've looked at the innerds of these things and they sure seem simple enough.  It's hard to imagine what might be wrong with the gauge. Could it be that my replacement CVR is bad? How can I test it?

2: Has anyone replaced these gauges with something more modern? I'd like the car to be as original as possible, but I want a driver. If there's no answer to #1 above, what are my alternatives?

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joew94th Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Fan Joined: Sep/23/2018 Location: Northern CA Status: Offline Points: 14	Post Options Post Reply Quote joew94th Report Post Thanks(0) Quote Reply Topic: Fuel and Temp guages not working Posted: Jan/23/2019 at 9:18pm
	I think this is my first post, so be gentle with me guys...err...gals I have a 68 Javelin that I'm messing with. I had the instrument cluster out to replace some lights. I also had some alternator issues I was dealing with. I've got those sorted out but now my Fuel and Temp gauges don't work. Looking at the wiring diagram I see they are both fed by the same CVR, so I replaced it. That didn't fix the problem, so I pulled both of them out and tried to test them using a bench-top power supply. I get nothing. Maybe I'm testing it incorrectly, but that's what I need advice on. I saw an earlier post on this subject and, sure enough I've got the old bi-metal gauges with what look like very delicate windings on them. My question are: 1: Is there a sure fire way to test these gauges to determine weather they're bad? I've looked at the innerds of these things and they sure seem simple enough. It's hard to imagine what might be wrong with the gauge. Could it be that my replacement CVR is bad? How can I test it? 2: Has anyone replaced these gauges with something more modern? I'd like the car to be as original as possible, but I want a driver. If there's no answer to #1 above, what are my alternatives?

pacerman Members Profile Send Private Message Find Members Posts Add to Buddy List Supporter of TheAMCForum Joined: Jul/03/2007 Location: United States Status: Offline Points: 9057	Post Options Post Reply Quote pacerman Report Post Thanks(0) Quote Reply Posted: Jan/23/2019 at 9:31pm
	Are you sure you have 12 volts to the positive terminal on the instrument cluster (feeding the CVR)? Is the pin which contacts the wiring harness plug firmly seated the circuit board? Do you have continuity between that pin and the downstream circuit? My thinking, since you say you have messed with/removed the cluster to replace some lamps, you may not have things completely corrected or that something in the circuit could have been accidentally damaged.
	Happiness is making something out of nothing.

addic Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Nut Joined: May/01/2008 Location: Kansas City Status: Offline Points: 370	Post Options Post Reply Quote addic Report Post Thanks(0) Quote Reply Posted: Jan/23/2019 at 9:41pm
	make sure nuts on gauge are tight, sometimes they get loose connection
	73 401 Pierre Cardin X P1 73 401 Pierre Cardin X F3 70 X 390 4spd 69 X 401 6 spd 69 AMX 401 auto BSO 73 AMX 401 4speed pc 73 vette 427sb 5spd 73 vette convt.? 08 zx14

Trader Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: May/15/2018 Location: Ontario Status: Offline Points: 6884	Post Options Post Reply Quote Trader Report Post Thanks(0) Quote Reply Posted: Jan/24/2019 at 3:43pm
	You can test each gauge with a usb power supply. At 5 VDC the fuel will go to full and the temp should read high (it's sensor is resistance so the higher the temperature the more resistance). On the back of the cluster is a common voltage regulator (actually a relay circuit cutting in and out to produce approximately 4.5 VDC). If you have 12 VDC to the cluster terminal and the gauges test OK, then it's likely the regulator (3 pin rectangular case). There are several posts on replacement electronic regulators and people building them. Another place to look is the pin on the board, over the years these sometimes work loose and break contact. Just careful re-soldering can fix this. Edited by Trader - Jan/24/2019 at 3:47pm

george w Members Profile Send Private Message Find Members Posts Add to Buddy List Supporter of TheAMCForum Joined: Jan/27/2013 Location: New Jersey Status: Offline Points: 2899	Post Options Post Reply Quote george w Report Post Thanks(0) Quote Reply Posted: Jan/24/2019 at 6:38pm
	The higher the temperature or gas level reading the LOWER the resistance at the sender. Very simple circuits. like addic said, check the pal nuts securing the gauge studs to the PCB. Loosen them and then retighten to snug to clean and to make sure connection is solid. Like Trader said, check the pins on the PCB that engage with the main connector plug. These can get loose and a light cleaning and soldering with rosin core solder will insure a good connection. You could have a bad CVR or oxidized connections there as well. Your problem should be relatively easy to locate and fix. No need to have to deal with aftermarket gauges.
	Long time AMC fan. Ambassador 343, AMX 390, Hornet 360, Spirit 304 and Javelin 390. All but javelin bought new.

Trader Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: May/15/2018 Location: Ontario Status: Offline Points: 6884	Post Options Post Reply Quote Trader Report Post Thanks(0) Quote Reply Posted: Jan/24/2019 at 9:46pm
	Thanks George, got it backwards.

joew94th Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Fan Joined: Sep/23/2018 Location: Northern CA Status: Offline Points: 14	Post Options Post Reply Quote joew94th Report Post Thanks(0) Quote Reply Posted: Jan/26/2019 at 1:30am
	Thanks for the tips everyone. I'm going to be pulling the cluster again within the next 2 months as I'm prepping for a paint job. I'll do some more testing then. I have a variable power supply that can put out 12 volts or 5 volts. I've pulled both gauges out of the cluster and tested them directly using the power supply, but I get nothing. It's hard to imagine the gauges going bad. There's just not much to them. Anyway, thanks again for the tips.

tomj Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jan/27/2010 Location: earth Status: Offline Points: 7544	Post Options Post Reply Quote tomj Report Post Thanks(0) Quote Reply Posted: Jan/27/2019 at 11:28pm
	with the gauges installed in the car, ground the fuel sender, it should read over-FULL. ground the wire at the temperature sender, and the temp gauge should fly to full-scale.
	1960 Rambler Super two-door wagon, OHV auto 1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com