87 S running hot, Cooling Fan Issue

[mhariush]

I know there are lots of threads on this already and I am trying to read up on them but I wanted to post in case someone had the same issue and worked it out.

So, my S has been running a bit hot since I got it. I always thought the fans worked, because they (or maybe at least one) turned on after the car was turned off.

Today I did the Clark's Fan relay test. Found that the fan's didn't run on High when jumpered as per the instructions. Swapped the relay with another, now they run high when jumpered.

While doing that I found an issue with the left fan, it wasn't running, only when I jiggled the connector. So I swapped out the fan with another working one. Now they both run when they should.

However, when the car runs, they go on late, and they seem to only go on low speed. Even when the car turns off and the temp gauge is above the middle (halfway between middle and third white line) they only go low speed.

I always thought the low speed was the high speed.

So, now what? Seems like the Relay works, or try with yet another one?

Check the resistors? Could the resistors be preventing it from running on high speed even though they can when jumpered?

Thanks!

UPDATE:
Fans not going on when the car start heating up. Does not kick in when temp goes past the mid mark.

What I've done:
Replaced Thermo Switch in radiator
Replaced both sensor in block
Replaced Fan Relay
Replaced one fan with a bad connection
Replaced Resistors with another set
Cleaned up the corrosion on one resistor wire.

[v2rocket_aka944]

might be the switch in the radiator, the late cars have 3 pins, one of which should be the high temperature (hi speed) switch.

[mhariush]

I forgot to mention: I replaced the Thermo Switch in the radiator with a new one, and also checked the waterpump thermostat. The switch and the thermostat have the same temp rating. Also replaced the two temp sensors in the block.

[v2rocket_aka944]

fans are supposed to run on low speed when car is off.

do they run at high speed when you push the AC snowflake button?

[mhariush]

oh, the other car i have right now, that i will part out runs the fans on high speed when the car is off. the fans run low speed when the ac is on.

[v2rocket_aka944]

try disconnecting the resistors entirely, just connect the wires on either side with another wire...see if they run high speed then?

[pfarah]

Sounds like a connection is on backwards. The fans should run on high when the AC is on and only low if required when the engine is off. Try this, turn the AC on with the engine off and ignition key turned on. Do both fans run high or low? They should run high.

[mhariush]

Double checked now. They fans go on low with the AC on. And low when the engine runs too.

Which connector could be backwards? The connectors on the fan only fit one way.

When I Jump the terminal 1 and 3 on the thermo switch connector, as per Clark's, the fans kick into high.

By the way, according to Clark's "Turn the ignition ON and place the air conditioning switch in the ON position. Both cooling fans should run in slow speed."

http://www.clarks-garage.com/pdf-manual/cool-01.pdf

[v2rocket_aka944]

Fan switch connector backwards? Relay backwards?

[mhariush]

The relay only goes one way. And the fan switch connector too has the plugs positioned so that it can only connect one way.

By the way, I put the old relay on the other (red) car that I've been driving around which usually is way cooler, and now it was as hot as the black car. So the old relay was def bad. the red car now has the one troubled fan from the black car, so it wasn't running as cool as it used to.

I think I'm going to try and swap the resistors...

[87m491]

Always good to check suspect fan resistor wiring.

[mhariush]

I'm checking the wiring. Also have a spare set of resistors, but they're just ceramic, can they fail?

[mhariush]

Just checked the wiring on the resistors. One wire on the second resistor (furthest from the battery) was corroded and really hard to remove. Culprit?

And holy sparks, i need to make it a rule to always disconnect the battery. I removed the resistor bracket and accidentally touched it on the battery terminal and a shower of sparks emitted. Scary.

Could this be the culprit? The fans DO kick into high speed when I jump the terminals though...

How to treat this corroded wire?

[87m491]

Ceramic doesn't just fail, but copper wiring does. Resistor wiring is notorious for rotting.

Originally Posted by mhariush

I'm checking the wiring. Also have a spare set of resistors, but they're just ceramic, can just fail?

[mhariush]

yeah looks like it's only the one wire that's very corroded. But the others don't look great either.

[87m491]

The treatment s replacement. Pull out the glove box and you'll see the other end of the harness. 4 pieces about 10" +- long each should do it.

[mhariush]

fun times

Alright, I'll get in there and replace them. What did you do with yours? Did you just get standard wires from home depot or similar?

[87m491]

Same gauge wire from your favorite supplier, soldered inside the cabin to good end of the harness and spade connecter under the hood. Make sure you somehow label the stub ends so you can reconnect the proper leads first time around.

[mhariush]

I found some good OEM wire. I have a spare harness I've started parting out so I'll use that, and keep the OEM look. Now just have to do the soldering, which I am not a fan of. It's hard...

[mhariush]

So, still working on this issue.

I didn't replace the resistor wires as I was hoping to be able to wait until I eventually remove the dash and replace them properly at that time.

I replaced the resistors with a set from another car that didn't overheat and cleaned up the connectors and the one corroded wire, then put some heat shrink tube on it, and the tip of the others. The corrosion in this wire isn't much worse than my other car and that's running fine...

I tried running the car in idle and the temp started creeping up. When it reached the mid mark, the cooling fans didn't go on. When it went past the mark, the cooling fans still didn't go on.

When I turn on AC the cooling fans go on low speed.

As mentioned above, I have replaced the thermo switch in the radiator, and the two sensors in the block.

What else could prevent the fans from kicking in when they're supposed to?