Oil Pressure Light does not work.

Cougar Community Classic Cougar Community Discussion
1

I have a 72 Cougar. Just dropped in a new motor. My oil psi light never worked so i installed an aftermarket oil psi gauge for peace of mind.

So motor is all good and oil psi is good so I thought I would try to get the oil psi light working.

I was able to reach behind the dash and pull the Oil psi and the brake light bulbs out. At first they read open while in their little holder. I removed the bulbs and they checked fine. I realized the copper contacts on the bulb socket were oxidized. I hit them on the buffing wheel and they shinned right up and measured good with the meter.

I reinstalled them but still no light. I have jumpered the oil psi switch and the brake light psi switch.

I tried to remove the instrument cluster, but I cant figure out how to get it out.

I have the dash pad off and the instrument lens off … Cant figure out how to remove instrument cluster.

Ideas???

2

Where do you have the oil pressure gauge plumbed into the engine? If it’s in the hole where the factory switch was located you will need to install a tee so you can run both the gauge and warning light.

3

That is not the issue. I have an aftermarket transducer installed in the motor. I have a jumper wire in the factory oil psi unit wire to ground. It should illuminate the oil psi bulb.

Also I have jumpered out the brake psi switch and the Brake dash light does not illuminate either.

4

I know this may sound silly but in more than one case I have seen people mistake the water temp sender with the oil pressure sender. In any event you need to unplug the wire you have jumpered and see if you have voltage between the wire and the block. It sounds like you will find zero volts. Next you follow the lead to the connector on the firewall and see if you have voltage there. Then check to see if you have voltage on the ground side of the light bulb socket, then confirm that you are getting voltage at the input side of the socket. You have to keep following the circuit until you find the break.

5

I measured the oil psi (Not the Temp sensor) wire. No voltage.

Also there is no connector on the firewall. Only a wire bundle that goes through the firewall.

Which leads me back to the instrument cluster. I did see on the wiring diagram that both the brake and the oil dash lights share the same power wire. So I suspect a possible broken wire/connection from the fuse box to the cluster. But I cant seem to figure out how to get the cluster out.

Anyone here ever remove the instrument cluster from a 71-73 Cougar?

Thanks for all the replies.

Chris

6

I have a set of 72 shop manuals if you need.

Do you have a good ground from the engine to firewall?

7

Bill, on a Cleveland the water temperature sender and oil pressure switch have different size threads.

8

Yes I have a #16 wire from the back of the head to a stud on the firewall.

If you have a shop manual for a 72 I would be interested in looking at the section on the instrument cluster or dash removal.

My email is topfuel388@gmail.com

Thanks in advance.

Chris

9

Wow!!!

I got the cluster out. FYI if your going to take your cluster out. Do not follow the shop manual. It tells you to unhook the spedo cable from under the dash. No way!!!. I took the dash pad and driver side vent tube off so I could reach in from the top. There is a trick to getting the spedo cable off the back of the cluster ( thank you youtube) and the big connector has 2 release clips one on each side. But its out.

Now for the real troublesooting.

10

The oil indicator lamp compares RUN-only voltage to that of the oil sending unit line. Some models also have a oil indicator proof-out circuit to prove that the bulb is still good, but only when in the CRANK position. So let’s discuss more of how the lamp works. On one side of the lamp, you have RUN-only (or sometimes ACC) voltage. On the other side, you have the sending unit line, which when connected to the sending unit, presents high resistance to ground. The bulb will work when one sees very low resistance at the sending unit or when you ground the sending unit. The proof-out circuit provides that ground signal to the signal line side of the bulb.

If you are truly seeing no bulb illumination when grounding the sending unit wire, then either the wire is broken somewhere between the lamp and the sending unit, or the other side of the lamp has no voltage, or the bulb is bad. Or…your circuit card is bad. I’ll wager its the latter if you have no proof-out signal when cranking.

11

Found it!!

burnt/torn trace on the cluster flexible pcb. right at the connector.

I think I can fix it with some soldering skills.

12

is there a way to post images here. For the next lucky person who has this issue?

13

Told ya!

14

Here is a picture of the culprit. Broken trace on the back of the cluster.

Also as a bonus. I wanted to install LED cluster bulbs in the top of each cluster pod. However they did not work. It turns out that the sockets are wired with the tip as (-) and the body (+).

Since I have the cluster out, the wires for the 4 cluster lights simply screw on to the back of the cluster. If you swap them, then the LEDS will work.

Thanks for all your input.

15

You can easily solder that but if you need one in the future we have at least 10 on hand. Glad you found it!

https://secure.cougarpartscatalog.com/71pcb.html?attribs=83

16

Ok Oil Psi light is fixed!! Thanks for all your help.

While I was at it, I wanted to verify the brake light bulb.

I assumed that it was like the oil psi light, jumper the switch out and it would light the bulb.

That does not appear to be the case. I have 12v on 1 side of the plug but the other side of the plug is not ground. ’

So I consulted the wiring diagram. The one pin is 12v through the “Brake” bulb but the other pin goes to the ignition switch cranking position.

Looks like the other pin gets grounded only while cranking.

How is it supposed to work?? Looks like the switch body itself is the current path.

I was able to ground the 12v side of the plug and the Brake light does light up so all that wiring and the bulb is good.

Let me know your thoughts.

17

OK so I have the brake and oil psi lights working properly.

Now I’m moving on to alternator.

Should the alternator light illuminate when the key is on?? And then turn off once the engine is running???


Mine never lights.

I tried to figure out how it was wired but the wiring diagram that I got from wccc is really confusing for the alt light.

18

Yes, that is how it works. It compares the output of the alternator to the RUN-only voltage coming from the ignition switch. When the key is in ACC, the light should not come on, but when you put it to RUN or CRANK, it should light up until the engine catches.

Some early models of Mustangs/Cougars compare ACC voltage to the alternator voltage, so in that case, turning the key to ACC should light it up. When the car is in CRANK mode, ACC power is turned off to save current/voltage to the starter motor.