Help! Swapping relay messed up LCD display

[vdogamr]

Sorry to make a new thread, but my question thread (How test cooling fan) has progressed to a HELP! thread. (Also sorry about the previous title's bad grammar )

So I made several mistakes. I was trying to follow directions about an 84 and not an 88. What I thought was the temperature switch was not. And now I wonder what relay I just replaced. All relays look alike, are they interchangeable?

Anyway, on to the problem. I bought a new relay from the auto parts store and swapped it with the relay I removed from the driverside top of the cooling fan. With my relay connected, my LCD acts like the backlights are blown and random individual LCDs flicker on and off for about 15 seconds until random ones stay on. All hard to see since it isn't backlit. With the relay out, the LCD doesn't come one at all. No backlights, no flickering, nothing.

What does this relay do? Why does it screw with my instrument cluster? All the fuses seem to be fine. Please ;help!


Oh, and I put back the old relay. Same problem. I guess I fried some computer system. Anyone know how much that could cost? This will teach me to remember to disconnect the battery when working on things.

 

[vdogamr]

Quoted from the other thread

I am unsure what relay you replaced.
On my '87 and '89 cars all the relays (fans , fuel pump , TCC ) are by the firewall;on the '90 + cars ,the fan relays are on the radiator shroud by the Drv side headlight.
I have never seen a C4 with a relay on top of the fan; possibly aftermarket

Here is a picture, just in case I am poorly describing its location. But any help on fixing the digital dash would be very apreciated. The car starts but if I did fry some computer system, I don't want to risk driving it.

 

[vdogamr]

Still working

So I have been trying to researh as much as I can. I tried turning on the brights and the indicator did display just fine. All the threads on this forum indicate that my cluster is not grounded. I would assume an easy way to confirm this is to test it at the fuse. Can I just stick a voltmeter in the fuse slots? Is that dangerous? Should I be able to see the faulty ground without removing the battery? How many different grounds will I need to check? :confused

Can lack of grounding cause the random LCD flickering. Once it stops, I usualy have partially lit up digitial numbers and single bars in the analog display. Eventually it all goes very black. It always repeats everytime I set the key to the on position. ;help

 

[XLR8]

Sorry you haven't received a response to your questions before now... everyone must be out driving their Vettes! :L

I can't help with the tech issues but let me see if I can rustle up a member or two that can. Stand by.....

BTW... no apologies necassary! Ask your questions and post away - that's what we're here for!!

Jane Ann

 

[So Bay Vetter]

Have you tried just disconnecting the battery ground for a few minutes then re-connecting? I know it sounds stupid but, simple things first. Also, are you using a factory service manual?

 

[vdogamr]

I have disconnected and reconnected the battery several times. In fact I was trying to get the dash out and had the battery disconnected the whole time. I was unsuccessful in removing the headlight knob. :confused

I don't have the FSM yet. I do have an owner's manual, the Chilton manual, and today the mail should have delived the Haynes manual. I am definitly going to try to find an FSM.

I am assuming the ECM that controls the LCD or the cluster itself is ruined, but I want to see what happens if I fix the backlights.

 

[Toms007]

Well, again I am going to have to defer to someone else on this matter. I believe that the 88s are way different from my 94. I am following your saga and feel terrible that I can not help.

 

[roger longman]

Hi, make sure you undo all screws, including those on the door side. The headlamp knob will just pry off.You may pull it off the trangular metal clip but don't worry, pry that off too and reinsert it into the plastic part prior to reassembly. Roger.

 

[vdogamr]

I got all the screws out. But no matter what I stick in that slot, it just seems I can't get the knob off. Do I push on the metal tab, do I pry on it, or do I use it as leverage in prying the knob?

So an article I read on corvettemagazine said not to use a light tester or a volt meter in the cluster fuse. How can I test if current is getting to the fuse?

I am thinking about taking apart the dash. If nothing else I can clean the contacts, re-solder loose connections, and replace the bulbs with the new low heat bulbs.

I took out the battery looking for a bad ground. But there are so many wires, and I have no idea what I am looking for.

What I don't understand is, if unplugging a bad relay turns off the LCDs then that must mean they are attached to the small current circut running through the relay. To me that doesn't make sense. But I ordered the FSM with Electronic Diagnostic companion.

Does anyone have any recommendations for a Corvette specialist in the greater Seattle area? Form the look of my car, this isn't going to be the first time I have need of one.

 

[Paul Higg]

I too with I could help. Like Tom I have a 94. However, when you swapped out the relay did the part numbers match? I have a lot of experience with relays. You may have swapped one with a relay that will allow more voltage to pass than the original one. In that case you may be looking at a new dash circuit board. If I had the FSM for your model I could look at the wiring diagrams and troubleshoot it in a New York minute, I live for that.

I also feel your pain. But see my next post about the screw that cost me $165 :confused

Paul

 

[gmjunkie]

Sorry you haven't received a response to your questions before now... everyone must be out driving their Vettes! :L


Jane Ann

Yep,I'm in the sunny south wasting fuel in my "American Made" Gas Guzzling Sports Car and Dodging a bunch of Non driving Northern Super Bowl fans!! :L:L:L

Sorry,I'll be back home at my data base in a few days!! Maybe!!

PS. vdogamr,In the mean time Check and Clean EVERY Ground to the Chassis and Engine,EVERY Fusible Link and connection,Every Fuse in the fuse panel!!
You'll have to probly remove the Left Wheel Splash Shields and the Battery Tray to find them all!! And don't forget the grounds on the back of the engine and links on the starter!!

PSS Insert a pick behind the locking tab on the knob and pry the knob off!!

 

[roger longman]

Hi, On my 88 I just pulled off the knob, which left behind the metal clip, which I then removed with pliers. The bulbs are not LCDS OEM are halogen. Roger.

 

[vdogamr]

Hurray!

I am so happy I got the knob off. I haven't actually done any important work afterward or fixed anything yet. But that doesn't make me any less happy. Turns out the fingernail is the best tool for the job. I now begin my journy into unknown electronics.

Also:
When it comes to looking for bad grounds, should I actually unscrew and re-screw the grounds. Or just assume that if they are tight then they are good?

 

[Paul Higg]

Unscrew the ground, look for corrosion on the ground terminal itself, clean it if needs be. Also do the same on the ground stud and nut. Clean them with a brass wire brush as brass is softer than steel. You want a perfect metal to metal connection, nice and clean.

Paul

 

[vdogamr]

However, when you swapped out the relay did the part numbers match? I have a lot of experience with relays. You may have swapped one with a relay that will allow more voltage to pass than the original one.

Thats a good question. I went to the auto parts store and said I needed a cooling fan relay. They said they had one in stock and that there were apparently 2 relays required, but that they were interchangeable. Now again I am not sure that the relay I swapped was a cooling fan relay at all, but I took the one they had and put it in place. It fit just as nicely as the other realy and it had a very similar picture on top with E connected to C, A not connected and D connected to F through the coil. As for numbers, no they were not the same. (I assumed different brands)
The one I put in had 912210 and 018 on it, and the one I replaced had 8060 and 14089936 on it. I tried Googling 912210, but didn't get too much info.

I wish I had more to report, but sometimes life gets in the way of doing car repairs.

 

[Paul Higg]

I think I remember using a site once that cross referenced relays. It was a while ago so I have no idea about the URL.

What's the latest on the dash?

Paul

 

[gmjunkie]

It fit just as nicely as the other realy and it had a very similar picture on top with E connected to C, A not connected and D connected to F through the coil. As for numbers, no they were not the same. (I assumed different brands)
The one I put in had 912210 and 018 on it, and the one I replaced had 8060 and 14089936 on it. I tried Googling 912210, but didn't get too much info.

I wish I had more to report, but sometimes life gets in the way of doing car repairs.

As long as the diagram on the top of each one are the same and go to the same places in the plug,you should be alright!! As far as the relay messing up the dash,the only thing I can think of would a bad ground in the cooling fan circuitry and feeding back through the dash!! As far as the digital dashes go's,they are prone to getting bad connections in the plugs in the back!! On more clusters than I've had to send off for repair, I've just removed,cleaned connections and put them back and that fixed it!!

PS
BAD Grounds make electronics do weird Sh*t!!~!!

 

[rmagee7]

the relay on mine is in front of the brake master cylinder and the curise module,in my manual it does say that it has two relays,and sitting here looking at it does but.......it dont say what months they changed over from the single relay to the dual,it gave me fits when my ecm went south on me. after replacing the ecm and direct wire to ground the fan relay and left it run all the time untill i had enough confidence that the ecm was going to be all right, unhooked the ground wire and everything was just peachy.first off do you have a single fan or is it a dual fan set up they changed so much in such a short time it's kinda hard to keep up with it all.if it;s a single fan i belive you only have one relay.the ecm has control over the fan the only time it dosent is when it fails [the ecm] when it does that the fan wont go into bypass untill i belive the temp gets to 240-250 then it kicks in.it might not be the relay at all. man i feel for ya before i got mine fixed i had stomach cramps all the time but you gotta remember knowledge is power,the more you know the stronger you are good luck!

 

[rmagee7]

junkie man i'm gonna get naild for this cause i've only done it once buut.....how in the world do you start a new thread ???????.......

 

[vdogamr]

I think I remember using a site once that cross referenced relays. It was a while ago so I have no idea about the URL.

What's the latest on the dash?

Paul

Busy at work. My car is at home in the garage with the battery and other pieces on the floor. Saddly waiting for me to get to it. I have a buddy that loves wiring his own circut boards, so I thought I would take my dash to him for some resoldering while I clean some grounds. Probably won't have anything to report till next week. But I am still not sure why there would even be a relay that, once removed, keeps the dash from comming on. If cleaning the cluster's connections and checking the grounds does no good. I will just pay someone to fix it.

P.S.
I have the dual fans.