GQ-ROD

When i got my 84 vette the cooling fan comes on all the time when the ignition key is on.

I want to fix this correctly however i will be installing a manual over ride switch in the car once i know the stock temp switch is working correctly.

Tested the relay and it does work as it should

12v blue wire supplies current from ignition switch to relay key on - yes. Key off no current on blue wire fans stop.

12v to dark green/white stripe wire ignition switch on ( grounded )- yes ( means coil is working, fans come on ).

No current at dark green/white wire if not grounded.- works as it should.

12v red wire with fusible link from batt TO relay- yes

12v black/red stripe wire FROM relay TO fan ignition key on - yes

So i've determined the dark green/white stripe wire is shorted to ground somewhere triggering the relay coil to give 12v to the fans, have to follow it to the temp switch on engine to see if it's a bad temp switch which is shorting to ground or if PO had just attached it to ground permanently.

Already bought the eckler's 200 degree temp switch kit ( i know pricey but it's the first thing i bought when i got the car. )

I looked at my fsm wiring diagrams but they are a little hard to follow.

My question is, the relay looks like the original style for this year ( not the later year style. ( pics to follow )

BUT there are 5 wires at the relay harness, i know that the a/c switch is also a ground point for the fans but

One wire at the relay looks like it was cut and taped up not being used is this an extra wire for 12v ?

if not where is it supposed to go? could this be to tie into the a/c high pressure switch ?

I ask because on another simpler wiring diagram posted by other members here, it looks like there should only be 4 wires at the relay total.

green with white stripe wire becomes lt green/blk then splits into tan for a/c switch and brown for eng coolant temp switch.

Thanks!

ccrazor

This is the colored drawing for the 84 from the electrical supplement to the FSM. If you have a ground on the dk grn/white all the time either the temp switch, a/c pressure switch or the wire to one or the other is shorted to ground. Try unplugging the two switches one at a time to narrow down which. Do you have a color for the extra wire, is it part of the original wire harness?? If you go to page 8A-15 of the FSM you will see the location of C100 and C115..

GQ-ROD

The extra wire is coming out of the relay all 5 wires look to be white ( dirty of course from age ).

I'll track down the ac wire as i did not see it so clearly, as well as the connectors and report back.

Thanks!

ccrazor

The location of the a/c switch is shown on page 8A-133 fig. 8a-119..

GQ-ROD

Thank you i was looking at the diagrams in the back of the fsm to trace wires, will test and report back!

GQ-ROD

Thanks, i appreciate the help !!

GQ-ROD

Ok managed to find the brown wire for the temp switch circuit in the lower wiring loom coming out FROM the firewall going up towards the windshield wiper motor area.

Will upload video soon.

I put 12v on this brown wire, ignition off, and the fan came on !!

I thought this was strange since i thought if i put 12v on the brown wire it should not activate relay since this wire is downstream after the relay.

So i'm assuming the coolant temp switch circuit is at fault and grounded, will follow it down to the switch testing as i go to see where exactly it's grounding out.

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I opened the thicker wiring loom going towards the front of the headlamps looking for the TAN wire which should be the ground for the ac pressure switch, i found 2 thick ones and one thin one.

The 2 thick ones had continuity, ignition off,

the thinner tan wire did not have continuity ( not sure why there are 3 or if i have the correct tan wire yet ).

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Pic of an ac switch passenger side close to heater blower motor, don't know if this is the high pressure or low pressure one.

Looked at the compressor and did not see any other switches.

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pic of the relay showing the wire that was taped off

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pic of relay showing all 5 wires

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GQ-ROD

Added this video i took of my progress, it's my first cell phone video upload please don't crucify me!!

http://s485.photobucket.com/albums/r...rcuitvideo.mp4

GQ-ROD

Will have to take a pic of the compressor tomorrow, it's odd i don't see the high pressure ac switch anywhere on the ac lines or compressor.

I did find out the socket that had been jumped is activating the compressor clutch when i apply 12v to it. Weird !!!

On diagram fig 8a-119 page 8a-133 in the fsa it shows on the ac line that socket connecting to the pressure switch the only thing that is there is a shrader valve. perhaps PO removed the valve then jumped the socket for some odd reason?

Also found the cooling fan switch connector it is not connected to the harness at the top over the ac compressor, should it be ??? is this where the ground is shared between the ac pressure switch and the fan temp switch ?

Tested it and shows continuity.

Not sure if the ac had been converted to R134a or not.

Will post pics tomorrow.

ccrazor

First, it appears that your fan relay has been moved by a previous owner, normally it is under the booster which makes it a little hard to get to. No idea what the extra wire is for unless it is joined to the red wire for a 12v supply. The harness you want for the pressure switch is the back one. The socket in the front corner by the head light looks like the socket for the under hood light, you should find another on the other side. You may have to pull the bottom of the breather to find the pressure switch (never had to find it, but like the temp. switch it should be a single wire).. The temperature switch is left of the dipstick.. Fig. 8A-10 page 8A-16. The plug with the red jumper looks like the plug for the high pressure switch, if it has spade connectors on each end of the wire..

GQ-ROD

Thanks so much for your help saved me hours of scratching my head, the hood lights do not come on when i open the hood so great call on that plug.

On that plug that was jumped yes i agree i think that is the high pressure switch plug, i think the PO may have just pulled out the switch and never replaced it though it doesn't make sense why he would jump it.

I'll jack the car up today and take a look, i checked last night and could not see the temp switch between cylinder 6 and 8, i did see a tan wire not brown so i'll check it today and report back.

Thank You !!!!!

GQ-ROD

Ok it just keeps getting better,

jacked the car up, looked for the temp switch next to the oil dipstick between cyl 6 and 8, it's not there !!!!

Looks like the po removed it and put a plug in the block correct me if i'm wrong please. Why on earth would anybody do this when the part is so cheap is beyond me, the same amount of work it takes to do this you might as well do it right the first time !!!

I also did not see the brown wire with the proper connector. Still have to follow the brown wire where it leads from the harness.

There is a TAN wire not brown wire attached to what looks like the top of the exhaust manifold bolt, have not removed it to test it yet.

Did also notice while i was under there that the knock sensor is NOT connected either and no connector to be found, this guy went crazy removing stuff all over !!!! got my work cut out for me.

Will disconnect it, test it, and report back.

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sorry for the blurry pic, difficult to get the camera phone up and close but this is the tan wire barely hanging on for dear life at the manifold bolt.

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you can make out the plug above this tan wire on the block

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GQ-ROD

Tested that tan wire and that's the ground point. Will check the rest the wiring to ensure it's good.

Disconnected wire and fans do not come on.

I won't be able to replace the temp switch until i order the pigtail connectors for it and the knock sensor.

Since i have to drain the coolant i'll change out the thermostat and do everything at once.

Stay tuned. and thank you for all your help i sincerely appreciate it !!!!

GQ-ROD

I finally ordered and got the temp switch kit from ecklers in,

I tried to remove the pipe plug using a 3/8 tip, 1/2 inch square head socket i ordered online.

NO GOOD !!!!!!!

Even with a 3 foot breaker bar it would not budge !!!

So called Corvette Masters and Robby was very nice and promptly answered my email request for a labor quote on removing it.

Same for the new knock sensor i received, no sense me trying to get the old one out, spill coolant then it breaks and i'm toast not being able to move the car and having to try to tap out the threads.

Every car is different so labor price may change which is why i am not listing it here, but if he can remove it the price is very reasonable for removing both. Even he admits they don't always come out easily.

I remembered that old song from the movie the gambler, know when to hold them and know when to fold them, ......I FOLD.

I think it's better to let a pro wrench this plug out since it may need some serious heat and elbow grease to get it out.

I did solder a new pigtail wire to the original tan wire which was grounded to the exhaust header by the PO, this way i can run that wire to the console for the temp switch manual over ride switch i'll be installing.

I'll update when it's done with pics.

84lover

I am having the same problem but I am needing to know if your guage cluster dims. I drove it without the relay connected and cluster didn't dim.
I replaced relay....temp switch....disconnected compressor completely and the fan still runs with key on or off

Hot Rod Roy

Probably won't do much good to ask GQ-ROD about your problem. He hasn't been here for 6 years. Let's go back to your previous post.

84lover

whenever I plugged in the relay it would push the contact in causing it to make a connection which made the fan run all of the time.
take the relay apart and hold the red wire contact to plug it in .