1972 Gremlin Gauges.

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   Hello all,
I recently picked up a 72 Gremlin with a 232. I just got it registered and have several issues.

Alt light keeps flashing on and off while at idle or driving. Stays solid like it should before starting. I checked the voltage at the battery while running and get ~14.5V

Gas gauge does not read. I pulled the connector off of the sending unit and checked voltage to ground and it bounces all over the place. I pulled the instrument cluster to replace and test all bulbs. I put 12V to the fuel gauge and it moves to full so the gauge works fine.

Temp gauge does not work. I do not seem to see a sensor on the engine anywhere. The only sensor I can find is what I assume is oil pressure on passenger side towards the back on the block.

Could I have a bad voltage regulator? The one on the car is a potted unit.

Thanks for any help on these issues.

Jim

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Jimjific Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Apprentice Joined: Jun/03/2022 Location: Albany Status: Offline Points: 38	Post Options Post Reply Quote Jimjific Report Post Thanks(0) Quote Reply Topic: 1972 Gremlin Gauges. Posted: Jul/05/2022 at 9:27am
	Hello all, I recently picked up a 72 Gremlin with a 232. I just got it registered and have several issues. Alt light keeps flashing on and off while at idle or driving. Stays solid like it should before starting. I checked the voltage at the battery while running and get ~14.5V Gas gauge does not read. I pulled the connector off of the sending unit and checked voltage to ground and it bounces all over the place. I pulled the instrument cluster to replace and test all bulbs. I put 12V to the fuel gauge and it moves to full so the gauge works fine. Temp gauge does not work. I do not seem to see a sensor on the engine anywhere. The only sensor I can find is what I assume is oil pressure on passenger side towards the back on the block. Could I have a bad voltage regulator? The one on the car is a potted unit. Thanks for any help on these issues. Jim

BrotherBamc Members Profile Send Private Message Find Members Posts Add to Buddy List Supporter of TheAMCForum Joined: Jan/22/2009 Location: Lewiston Status: Offline Points: 2248	Post Options Post Reply Quote BrotherBamc Report Post Thanks(0) Quote Reply Posted: Jul/05/2022 at 9:10pm
	Sending unit for the water temp should be on the front of the head by the thermostat housing. At least that's where mine used to be on my 258 Fuel gauge is probably the sending unit. They're known to go bad. As far as your alt light, I'd say it might be a short somewhere in the wiring. You're definitely getting good volts to the battery. Ya gotta love these old cars. Good score on the Gremmy..!!
	77 CJ5 360 73 Gremlin 401 4 speed 2006 Dodge Magnum R/T AWD My Garage

tomj Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jan/27/2010 Location: earth Status: Offline Points: 7539	Post Options Post Reply Quote tomj Report Post Thanks(0) Quote Reply Posted: Jul/05/2022 at 11:21pm
	The dash voltage regulator does not put out a steady voltage, it pulsates on/off 12v/0v so you cannot check them with a voltmeter! The simplest test for gauges is to momentarily ground the sensor wire. Gauge should read full scale. Pull wire off; gauge pointer falls off the left edge.
	1960 Rambler Super two-door wagon, OHV auto 1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com

Jimjific Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Apprentice Joined: Jun/03/2022 Location: Albany Status: Offline Points: 38	Post Options Post Reply Quote Jimjific Report Post Thanks(0) Quote Reply Posted: Jul/13/2022 at 8:38am
	An update. I took the gauge cluster out and went through everything and reinstalled. The temp gauge works I just didn't notice the movement. Alt light was off and this morning I went to do it's first "long" trip (about 40 miles round trip to work) and there was dew on the window so I turned on the wipers and they didn't want to park and slowly kept moving when I turned the switch off. Then I noticed the ALT light came back on steady. Gets brighter with RPM. I've never had an old car not park it's wipers. It also looks like the two separate speeds doesn't work. They seem to be the same on both positions. Can the ALT light and wiper issue be related? Seems weird, but electrical is always a pain. A cancelled the trip since I do not want to get stranded. Took the 67 GT Cougar instead. Thanks, Jim 72 232 Gremlin

1948kaiser Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jan/25/2015 Location: south west flor Status: Offline Points: 833	Post Options Post Reply Quote 1948kaiser Report Post Thanks(0) Quote Reply Posted: Jul/13/2022 at 10:17am
	have you cleaned all the connections including the fuze panel under the left side of the dash?

Jimjific Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Apprentice Joined: Jun/03/2022 Location: Albany Status: Offline Points: 38	Post Options Post Reply Quote Jimjific Report Post Thanks(0) Quote Reply Posted: Jul/13/2022 at 12:15pm
	No I have not. I did check all the fuses though for continuity. I will pull them and clean the contacts. Does anyone know if these cars have a resistor or resistor wire? Thank you, Jim

blumontag Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Mar/05/2013 Location: minneapolis Status: Offline Points: 837	Post Options Post Reply Quote blumontag Report Post Thanks(0) Quote Reply Posted: Jul/13/2022 at 1:44pm
	Just a thought... had similar no-park/ incorrect speed situation after messing with my gauge cluster. I had a few unused extra wires in the dash (for seat belt buzzer probably) and I connected one of them instead of the correct wire into one of the ground lugs on back of the cluster switches. (And it was a purple wire, not black, that goes to my wiper pump). Once I got the connections on back of the cluster switches correct, everything worked as it should.
	72 Gremlin X

Jimjific Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Apprentice Joined: Jun/03/2022 Location: Albany Status: Offline Points: 38	Post Options Post Reply Quote Jimjific Report Post Thanks(0) Quote Reply Posted: Jul/13/2022 at 3:35pm
	Hmmm. Interesting. I will have to check this out. I did notice a weird wiring issue. The wire going to the bulb for the "optic" for the wiper and headlight switch was cut and twisted with a brown wire. I didn't know why this would be so I put it back how I found it. That bulb I bench tested does not light up though with the headlight switch like it should. I wonder if that is the brown wire for the wipers. I will have to investigate. Thanks for the thoughts and the diagram. Jim

FSJunkie Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jan/09/2011 Location: Flagstaff, AZ Status: Offline Points: 4742	Post Options Post Reply Quote FSJunkie Report Post Thanks(0) Quote Reply Posted: Jul/14/2022 at 1:50am
	So, first off there are two voltage regulators. One is the main voltage regulator mounted to the inside of the fender that controls the alternator output voltage. 14.5 volts is about right. The second regulator is inside one of the gauges...either the fuel or the temp gauge, I forget which. It's a mechanical regulator with a set of contacts that switch on and off several times per second...14v...0v...14v...0v... averaging to about 7 volts. This is the voltage that the temp and fuel gauges run on. The gauges react slowly enough that they do not pulse with the regulator switching on and off. The alternator light going on and off is most likely caused by a loose connection at the alternator, regulator, or starter relay, or a regulator that is failing. It's a solid-state regulator and they last a very long time, but they can get intermittent. A failure of the regulator for the gauges will cause both the fuel and temp gauges to not work, since the regulator is common to both gauges. The regulator will usually either stick open and the gauges always read cold, or stick closed, and the gauges always read pegged...until they burn out. Then they read cold forever. Full car voltage (14v) for more than a few seconds will burn out the gauges. Gauges that read, but read too low, is usually caused by the sensor going bad, the sensor having a poor ground, or the connector at the sensor making poor contact. Everything must be clean, tight, and free of corrosion. Wipers not parking is usually caused by the park contacts inside the wiper motor sticking because of old grease on the mechanism or a failure of the wiper switch.
	1955 Packard 1966 Marlin 1972 Wagoneer 1973 Ambassador 1977 Hornet 1982 Concord D/L 1984 Eagle Limited

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: Jul/14/2022 at 10:45am
	The wiper switch housing requires a ground. There may be a copper or metal ground jumper behind the dash that the switch shaft passes through. That could be missing.
	Long time AMC fan. Ambassador 343, AMX 390, Hornet 360, Spirit 304 and Javelin 390. All but javelin bought new.