Check engine light

[91merc]

Does anybody know what this relay under the glovebox on my 85 GM does and why it made the check engine light come on when I replaced the old busted one?

[Arquemann]

The engine light on an '85 comes on from low oil pressure and/or high coolant temperature. It has nothing to do with the engine computer or other "smarter" electronics.
So either you have a wiring gremlin or your engine light didn't get signal properly before.

[91merc]

The engine light on an '85 comes on from low oil pressure and/or high coolant temperature. It has nothing to do with the engine computer or other "smarter" electronics.
So either you have a wiring gremlin or your engine light didn't get signal properly before.

I forgot to mention that I have an 88 cluster that has the yellow “check engine” light in place of the original cluster’s “check oil level” light but my oil level is good so hopefully it’s just the sensor or something

[Arquemann]

'85 engine light doesn't blink on test, but a test light should (if done correctly).
I have no idea how an '88 cluster differs from '85.

[sly]

Unless you took the time to wire the diagnostic light to the correct wire on the diagnostic port, you are still working with a low oil level light that is just labeled wrong. The sensor for that is on the oil pan and I think is normally open (when oil is low, it's open). So if the wire harness to it is damaged or came loose, that would be why the light is now on.

[91merc]

This is the original cluster compared to the one that’s in the car

[Arquemann]

W̶h̶a̶t̶ ̶t̶h̶e̶ ̶h̶e̶c̶k̶,̶ ̶y̶o̶u̶'̶v̶e̶ ̶g̶o̶t̶ ̶2̶ ̶e̶n̶g̶i̶n̶e̶ ̶l̶i̶g̶h̶t̶s̶?̶ ̶T̶h̶e̶ ̶l̶o̶w̶e̶r̶ ̶o̶n̶e̶ ̶i̶s̶ ̶s̶u̶p̶p̶o̶s̶e̶d̶ ̶t̶o̶ ̶b̶e̶ ̶a̶n̶ ̶o̶i̶l̶ ̶l̶i̶g̶h̶t̶ ̶o̶n̶ ̶t̶h̶e̶ ̶o̶l̶d̶ ̶a̶n̶d̶ ̶n̶e̶w̶ ̶c̶l̶u̶s̶t̶e̶r̶s̶.̶
A̶t̶ ̶t̶h̶i̶s̶ ̶p̶o̶i̶n̶t̶ ̶I̶'̶d̶ ̶j̶u̶s̶t̶ ̶c̶h̶e̶c̶k̶ ̶t̶h̶e̶ ̶o̶i̶l̶ ̶l̶e̶v̶e̶l̶ ̶s̶e̶n̶d̶e̶r̶ ̶a̶n̶d̶ ̶w̶i̶r̶i̶n̶g̶.̶

EDIT: That's an '89 cluster by the looks of it.
Probably still check the oil level sender and wiring.

[sly]

So is your car an 85 or is the cluster an 85? If the car is an 85, then check the oil level sensor. If the car is 88-91, that light shouldn't be on constant except when the car is on but not running.

[91merc]

So is your car an 85 or is the cluster an 85? If the car is an 85, then check the oil level sensor. If the car is 88-91, that light shouldn't be on constant except when the car is on but not running.

The car is an 85 with a newer cluster

[slack]

I'd trace the circuit board on the back of the 88 cluster from the check engine light bulb to the connector then do the same on the 85 cluster from the oil light bulb. If they go to the same pin, the check engine light is on because your low oil light is on. Or you could plug the 85 cluster back in and see if the check oil light stays on solid as well.

Like the others said, the oil sensor is on the oil pan. If the sensor seems fine, then some wiring got weird from there to the light.

Just a thought if it's not anything with the oil level sensor...

On my 89 Crown Vic, I went the opposite way as you. I put in an early 80s police speedo in place of my original one. For mine, I used my original backing flex circuit board/plastic housing with the older speedometer's face and guts. Never tried on a grand marquis one before, but maybe you could do the same if the newer cluster's bulb traces don't line up correctly on the connector? (Use the 85 flex circuit/back plastic with the 88's guts and top plastic) Here's a link to the post from back then: http://www.grandmarq.net/vb/forum/te...60#post1065060

[91merc]

Does anybody know what that relay I showed is supposed to be for? Lol

[friskyfrankie]

If you have the wiring diagrams, you can tell what it is for by wire colors and location of the relay.

[sly]

+1 I have no clue. I had an 88, but it didn't have a relay there.

[gadget73]

If thats wired to the check oil light circuit, its the relay for that circuit. I don't have the EVTM handy but there is a relay involved in that system, and I guess you found it. I've never had to look into how all that works beyond the sensor in the pan or damaged wiring to it.

[91merc]

I'd trace the circuit board on the back of the 88 cluster from the check engine light bulb to the connector then do the same on the 85 cluster from the oil light bulb. If they go to the same pin, the check engine light is on because your low oil light is on. Or you could plug the 85 cluster back in and see if the check oil light stays on solid as well.

Like the others said, the oil sensor is on the oil pan. If the sensor seems fine, then some wiring got weird from there to the light.

Just a thought if it's not anything with the oil level sensor...

On my 89 Crown Vic, I went the opposite way as you. I put in an early 80s police speedo in place of my original one. For mine, I used my original backing flex circuit board/plastic housing with the older speedometer's face and guts. Never tried on a grand marquis one before, but maybe you could do the same if the newer cluster's bulb traces don't line up correctly on the connector? (Use the 85 flex circuit/back plastic with the 88's guts and top plastic) Here's a link to the post from back then: http://www.grandmarq.net/vb/forum/te...60#post1065060

well you see, the reason I got the new cluster is because the copper started lifting off the membrane in a lot of places on my 85 cluster and melted in a couple spots too and that’s why I changed it