- This topic has 11 replies, 5 voices, and was last updated 10 years, 8 months ago by
.
-
Topic
-
When I got my 94 Mustang GT the temp and oil pressure gauge would would stay close to the high limit but not change – so,I figured “Ok, that’s just how they read.” Then after a month or so after checking a bunch of other stuff, both gauges started going to mid-scale and they seemed happy with that. Today, the oil pressure gauge was back to pretty high (like when I first got the car) and the temp gauge climbed near the high limit (also like when I first got the car) but stopped (never went beyond 3/4 – not in red area). The car did not overheat and there is plenty of coolant. I am figuring faulty gauges or faulty sending units or some kind of current transfer from other wiring. When the oil pressure gauge had dropped to mid-range (a month ago)and stayed there, I was thinking oh, well, the oil changes made a difference by getting any gunk out of the engine but now I’m back to where I started. As for the temp gauge, I really have no idea. I’m just glad that it stops moving at a certain point, and continues to run fine. Also, the gauge needles don’t bounce around so I don’t think it’s a loose wire. Any great (but simple to do) ideas?
-
Replies
-
Ah ha! This AM when gauges were reading “hi” (temp and oil pressure) the lights and heat were both on. I took the car out just now and experimented. If the lights and heat are on the gauges for oil pressure and temp read high. But turn off the lights and heat, and the gauges return to “normal” range. It’s got to be parasitic current coming from the other wiring. Not something I plan to fix but (but will watch it for other problems. So I may have discovered my own answer. Well, at least to this issue with this car. 🙂
Look around under the hood for any wires (big or small) that simply bolt to the engine, body or transmission. Each one you find, take it loose and clean the connection with sandpaper. Maybe apply a little grease before reassembling. Don’t try starting the car with any of these wires (grounds) detached.
Thanks. Actually there are a number of wires under the hood that are not part of the original equipment. I think they are mainly for getting power to an aftermarket radio. Also, under the dash there are some wires that probably are also not original to the car. I’ll probably let my mechanic look at those some time – I really know nothing about how to check what goes where as far as under dash wiring is concerned.
Here are some things to look at. I know you did not over heat.
http://www.ericthecarguy.com/faq/what-to-do-when-your-engine-overheats
If the oil pressure sending unit only has 1 wire, it’s a switch and no matter what the oil pressure if there is any will read the same spot. Not saying this is the case, but it is a possibility. Oil pressure would be changed with the temperature.
Now to quote a tech I worked with, this is according to his GM training “Gauges are simply there for the customers amusement.”
I guess a bit of it would depend on what exactly you mean by “high”. are we talking into the red zone.
Both oil pressure gauge and temp gauge had been in the what I call the “worry area.” Not in the red zone but close (say 1 o’clock if 2 o’clock is red). Then after a month or two of ownership (while working on other stuff on the car), they both went to straight up (12 o’clock). The surprise was earlier in the week when they both returned to 1 o’clock – but later experiment it seemed only related to when lights and heater were on. With both off, both gauges slowly returned to 12 o’clock). I’m still betting it parasitic current from other wiring somewhere. I figure my gauges are just more amusing than those in other cars – I enjoyed your tech’s quote 🙂
By any chance do you have an aftermarket stereo installed? If so, check it’s wiring. I’ve seen many botched stereo installs cause problems like this.
Hi Eric – yes. But it was also wired directly to battery (fuse in wire) but I disconnected that when I first got the car (I would hear loud pop when starting the car so I just disconnected it). It reminded me the way I would wire up stereos and CB’s back when I was a teenager. The radio would work and I never burned a car to the ground – otherwise it probably was not done that well.
This is off of the forum.corral.net site (I guess the corral is where they keep Mustangs)
“To expand on the degrading wiring comment. As your grounds start to degrade, the pressure will start to read higher on the gauge. If the grounds start to get too bad or get loose, your oil pressure and temp gauges will both show dangerously high, when in reality, it’s just the resistance of the circuit.”
In addition to the power hook up there are other hook ups for radios such as an extra power wire for the radio memory or clock. They also sometimes get wired into the interior illumination circuit which is where it can connect with and mess with the other components inside the dash. There is also often a lead for a power antenna. These are the connections that often get botched. You might try removing the radio and seeing if you still have the problem. If you don’t, you know where to start looking for the problem.
- You must be logged in to reply to this topic.