Ammeter Doesn't Work.
Thread Starter
Safety Car
Joined: Mar 2005
Posts: 4,255
Likes: 82
From: Brampton Ont.
Ammeter Doesn't Work.
Car was stored for 27 years and have since don't a body off. When I finally started the engine I noticed the ammeter didn't work.
I'm not that great at electrical but I did the following.
Installed a new battery as it needed one anyway.
Turned high beams/lights on, fan on high, no change in gauge movement.
Tested voltage at alternator and found it charging at 14.1 volt. I know it's an amp, not a volt gauge.
Replaced existing ammeter with new and still doesn't work.
Any suggestions on troubleshooting.
I'm not that great at electrical but I did the following.
Installed a new battery as it needed one anyway.
Turned high beams/lights on, fan on high, no change in gauge movement.
Tested voltage at alternator and found it charging at 14.1 volt. I know it's an amp, not a volt gauge.
Replaced existing ammeter with new and still doesn't work.
Any suggestions on troubleshooting.
Race Director
Joined: Apr 2009
Posts: 19,294
Likes: 2,753
From: Charlotte NC
You have to verify that the wires that a re going to the ammeter have power on them as they should.....use your wiring diagram and check that out. One wire will be a black wire and the other will be a black wire with a white stripe...if I am not mistaken.
I do not trust the new gauges due to where they are made......but in order for the gauge to work...battery power MUST be on both of the wires that go to the ammeter.
DUB
I do not trust the new gauges due to where they are made......but in order for the gauge to work...battery power MUST be on both of the wires that go to the ammeter.
DUB
Thread Starter
Safety Car
Joined: Mar 2005
Posts: 4,255
Likes: 82
From: Brampton Ont.
Thanks for the reply Dub, I'll have to open the center dash and check for power.
I was hoping there was an easier way in that there was an inline fuse somewhere that I could check first before opening up the center dash.
I was hoping there was an easier way in that there was an inline fuse somewhere that I could check first before opening up the center dash.
Race Director
Joined: Apr 2007
Posts: 11,150
Likes: 890
From: South Western Ontario
The most likely problem is the fusible links on the wires. The ammeter wires both connect to the main red charging/power wires under the hood. I believe on a 75 the black/white wire connection is on the left fender connected just downstream from the alternator and the black wire is connected along the firewall. Both wires should have a fusible link at the end making the connection.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,117
From: Crossville TN
The two signal wires going to the ammeter pass thru the firewall connector. If you separate that connector and find the terminals for those ammeter wires, you can use a penlight battery to make quick contact to the ammeter and see if the needle moves or not. If it does not, there is most likely a problem with the ammeter, itself (unlikely to be the wiring on the interior side). If the needle moves, the meter itself is fine, but there is a problem getting the signal from the engine wiring harness. {Using this test method avoids opening up the gauge cluster area until it is known that the problem lies there.}
If that is the case, the fusible links in that circuit should be checked. [Remember that when a fusible-link fails, the wire will melt inside the insulation; the insulation may be darkened, but it will NOT melt and may appear intact.]
If the links check OK and the car functions fine electrically, there must be a faulty connection or wire in the current sensing wiring.
If that is the case, the fusible links in that circuit should be checked. [Remember that when a fusible-link fails, the wire will melt inside the insulation; the insulation may be darkened, but it will NOT melt and may appear intact.]
If the links check OK and the car functions fine electrically, there must be a faulty connection or wire in the current sensing wiring.
Last edited by 7T1vette; Sep 12, 2017 at 10:31 PM.
