Temp Needle Jumping
Thread Starter
Pro
Joined: Jun 2004
Posts: 561
Likes: 1
From: No longer in Heaven
Temp Needle Jumping
My temperature needle has begun jumping uncontrollably. It's a '69 L71, all original, guage has always worked (had car for 3 years) actually all guages work, and recently it has just gone wacky. It will swipe back and forth almost the full path of cold and hot and jump around, and then just drop back to cold (left side of guage) and not show any reading. Then all of a sudden it will start jumping around again.
Any thoughts short of taking it out for repair/replace?
In that 435, I really don't like not knowing what the temp is.
Any thoughts short of taking it out for repair/replace?
In that 435, I really don't like not knowing what the temp is.
Melting Slicks
Joined: May 2002
Posts: 2,716
Likes: 121
From: Sulphur LA
St. Jude Donor '05-'06,'11,'13-'14,'16,'18,'19,'24, '25
check the electrical connection at the sending unit and check the motor ground at the pass side front of the block to the motor mount at the frame.
You can use a multi-meter to check the sender for a steady ohm reading to make sure its good.
If everything checks out good it may be time to get into the dash
Neal
You can use a multi-meter to check the sender for a steady ohm reading to make sure its good.
If everything checks out good it may be time to get into the dash
Neal
Pro
Joined: Jun 2009
Posts: 613
Likes: 3
From: Fleetwood PA
I had the exact same problem in my 68 L71 car. It turn out the temp sender wire had rubbed through and was intermittently grounding. The needle would jump back and forth just like you discribed, then would read right, then back to jumping. I'd start at the sender and work your way back the wire checking for any place it might be split or grounding.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,112
From: Crossville TN
Most likely, the connector at the temp sender is loose or the wire going into it is almost broken off. As mentioned, you have an intermittant signal condition occurring...it's a wiring issue.
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,847
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
I'm going with everyone above, but maybe take it a bit further.
Your wire running to the sending unit is the input wire for the dash unit. If this wire is off the sender the gauge will read cold. If it falls off and grounds out the gauge will read hot.
Your comment about the gauge fluttering and then going cold tells me the wire is still hooked up to the sending unit and there is a break somewhere. More than likely it will break all the way through, fall and ground out. When this happens you'll have a gauge that is pegged and flutters.
So go to the sender and check the wire all the way back to the firewall. I feel sure you'll find your issue.
Willcox
Your wire running to the sending unit is the input wire for the dash unit. If this wire is off the sender the gauge will read cold. If it falls off and grounds out the gauge will read hot.
Your comment about the gauge fluttering and then going cold tells me the wire is still hooked up to the sending unit and there is a break somewhere. More than likely it will break all the way through, fall and ground out. When this happens you'll have a gauge that is pegged and flutters.
So go to the sender and check the wire all the way back to the firewall. I feel sure you'll find your issue.
Willcox
Thread Starter
Pro
Joined: Jun 2004
Posts: 561
Likes: 1
From: No longer in Heaven
I'm going with everyone above, but maybe take it a bit further.
Your wire running to the sending unit is the input wire for the dash unit. If this wire is off the sender the gauge will read cold. If it falls off and grounds out the gauge will read hot.
Your comment about the gauge fluttering and then going cold tells me the wire is still hooked up to the sending unit and there is a break somewhere. More than likely it will break all the way through, fall and ground out. When this happens you'll have a gauge that is pegged and flutters.
So go to the sender and check the wire all the way back to the firewall. I feel sure you'll find your issue.
Willcox
Your wire running to the sending unit is the input wire for the dash unit. If this wire is off the sender the gauge will read cold. If it falls off and grounds out the gauge will read hot.
Your comment about the gauge fluttering and then going cold tells me the wire is still hooked up to the sending unit and there is a break somewhere. More than likely it will break all the way through, fall and ground out. When this happens you'll have a gauge that is pegged and flutters.
So go to the sender and check the wire all the way back to the firewall. I feel sure you'll find your issue.
Willcox
Thanks to all replys. You were all basically right. The connector clamp to the sending unit was loose and must have been moving around from vibration and motion causing intermittant disconnection. I bent it a little bit with a pliers, it slipped on the unit snug and then the guage worked perfectly.
Thanks again to you brilliant members!
