Power to fan, not coming on and kick on when CTS is disconnected

[minigts]

Tested two different computers, checked relays and do continuity for all wires connected to the relay and it won't kick on or provide power. I tested it on my 87 Lancer and the fan comes on as soon as you disconnect the plug to the CTS. Car is an 88 CSX T with the SMEC. Thoughts on what to check next?

[wheming]

Sounds weird.
Does the fan come on when the engine temp gets high?

[minigts]

From what he told us, it will not come on. We didn't want to try and get the car hot to test, so we spent time trying to diagnose why the fan wouldn't come on in the basic sense disconnecting the CTS.

[wheming]

When you unplugged the CTS, did the car change at all? When you unplug the CTS and the ecu sees the failed sensor it defaults and it does change the timing and other things. Should have made some kind of operational difference like a brief stumble or something. When the fan comes on, it kicks the AIS, so since it didn't, you might not have seen a change in idle rpm but it still should have defaulted to the failed CTS value. Did the fan relay even click when you unplugged CTS?

Do you have a drb? You can test the fan from actuator tests.
I forget which terminal it is, but grounding a terminal on the relay starts the fan.

You did check the fan to see that it does work if you power with 12v with some test leads directly to battery?

[82 Rampage]

Applying ground directly to the relay it activates and we get 12 volts @ the fan connector. When we unplug the cts the relay never activates. We verified all the wires going in and out of the relay are good with an ohm meter end to end. Verified all grounds going to the smec are good. I'm going back friday with a known good smec.

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[A.J.]

Tested two different computers, checked relays and do continuity for all wires connected to the relay and it won't kick on or provide power. I tested it on my 87 Lancer and the fan comes on as soon as you disconnect the plug to the CTS. Car is an 88 CSX T with the SMEC. Thoughts on what to check next?

Are you getting power to the relay? Fusible link might be blown. If you get power and ground to the fan (by unplugging the CTS) and the fan still won't come on, test the fan by itself. If the fan doesn't work with power and ground jumper wires hooked up the fan is bad. If the fan works you could have a bad fan relay. The relay could provide power, enough to show power on a meter, but once you put a load on the system the contacts in the relay "break" because the contacts are bad when amperage spikes.

[mrchriswray]

the relays are good because i have changed them twice ( i am owner of the car in question). it does not have a rad or coolant in it at the moment so we couldnt run the car long enough for the fans to come on or else the engine would have gone into chernobyl meltdown mode (always not a good plan) we tested the relay by itself and it is good. i have tested the fan with a powerprobe and it is good. (great tool to have by the way. worth every penny.)

[A.J.]

we tested the relay by itself and it is good.

How? I've been burned in the past by only testing a relay for voltage and not load testing the circuit. Are you getting power to the fan through the relay when you unplug the CTS?

[82 Rampage]

It gets zero volts unless you manually ground the relay. We can worry about the fan being good or bad once we even get it to turn the relay on. I think the smec is bad, which I will verify friday.

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[mrchriswray]

Are you getting power to the fan through the relay when you unplug the CTS?

the fan is not coming on when you pull the plug for the CTS.

[82 Rampage]

No

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[black86glhs]

To clarify....You have good power and ground on the signal circuit of the relay, correct?
If you put power to the Batt side of the fan motor, it works, correct?
Have you guys verified the grounds are all good for these circuits?

[82 Rampage]

If we manually ground the relay it works. All the grounds going in to the smec are good. No ground on output of smec to the relay. Verified the ground wire from the smec to the relay is good with an ohm meter.

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[cordes]

Is the fan supposed to come on when you unplug the CTS and the car isn't running? If you flip the key forward and the fuel pump primes, the SMEC is almost certainly good.

[mrchriswray]

Is the fan supposed to come on when you unplug the CTS and the car isn't running?

we tried it on two different cars by pulling the plug on the CTS and the cars wernt running at the time and they both kicked on in both cars

[cordes]

You have tested the continuity between the ground on. The relay and the SMEC right? Have you visually inspected the wires? Perhaps it can't handle even the slightest load even though it tests good continuity wise?

[black86glhs]

If we manually ground the relay it works. All the grounds going in to the smec are good. No ground on output of smec to the relay. Verified the ground wire from the smec to the relay is good with an ohm meter.

Sent from my SM-G920P using TapatalkBeen screwed by that exact statement before and I made it. I have honestly seen 1-2 strands give a continuity reading but won't power the circuit. Saw it on an IAC circuit on a buick. Ran a jumper wire from the connector to the ECM and the idle raised when the a/c was turned on. It may not be it, but running a wire from it to the SMEC would eliminate it.

[cordes]

Been screwed by that exact statement before and I made it. I have honestly seen 1-2 strands give a continuity reading but won't power the circuit. Saw it on an IAC circuit on a buick. Ran a jumper wire from the connector to the ECM and the idle raised when the a/c was turned on. It may not be it, but running a wire from it to the SMEC would eliminate it.

I'm convinced that this is what was causing my old GLHT to cut out at 6PSI.

[82 Rampage]

Did some more testing today. If you manually apply a ground to pin #57 of the smec, the relay activates and the fan runs. This means that the wiring to and from the relay and the fan motor are good. For some reason the smec is not applying ground to pin #57 like it should. We used a known good smec verified on my GLHS still only works as discribed above.

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[A.J.]

There must be a problem with wiring somewhere on the car. Maybe grounds to to SMEC are bad? There's no way two SMECs in a row are bad.

[black86glhs]

Did some more testing today. If you manually apply a ground to pin #57 of the smec, the relay activates and the fan runs. This means that the wiring to and from the relay and the fan motor are good. For some reason the smec is not applying ground to pin #57 like it should. We used a known good smec verified on my GLHS still only works as discribed above.

Sent from my SM-G920P using TapatalkPull all the grounds and clean them. I know it showed good continuity, but it eliminates on thing on the list. Make sure all the connection are good in the connectors. Had a LM that had spread terminals.

[cordes]

So at this point you know for sure it's not grounding through the SMEC. As others have said, clean up the grounds. I'm still at a loss with this whole deal though.

[Force Fed Mopar]

Do you have all your grounds hooked up? Injector rail, cylinder head, trans. Also make sure the ground straps are installed that connect the engine to the body, and make sure the battery negative terminal is grounded to the body also, not just to the engine.

[RattFink]

Did some more testing today. If you manually apply a ground to pin #57 of the smec, the relay activates and the fan runs. This means that the wiring to and from the relay and the fan motor are good. For some reason the smec is not applying ground to pin #57 like it should. We used a known good smec verified on my GLHS still only works as discribed above.

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How are you manually applying the ground? Via back-probing with the smec plugged in still? Or with the smec unplugged? Sounds like the terminals on pin 57 are not making a good connection with the smec, it's the only thing that makes sense at this point.

[82 Rampage]

Back probing with it plugged in, looked @ the pin in the connector, it looks better than all the others around it. Does that connector come apart or the pins just latch down in it?

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[Vigo]

Maybe i am a bit late to this thread to be saying this now but why has noone ever questioned the CTS circuit itself? All it has to do is show some kind of resistance number that is within the huge resistance range of a CTS, and the computer would think it was always hooked up whether it was plugged in or not.

It would be very easy to diagnose this with any kind of scan tool whatsoever. Which, from buying both, i'll tell you that a used scanner that will work on these cars is basically the same price as a spare computer anyway.

If you know how to back 60-way terminals out i would back out one of the CTS circuit wires to cause an open circuit AT the computer and see if it then turns on the fan. That rules out the possibility of the CTS circuit having some sort of high-resistance short that would simulate the CTS being hooked up.

[mrchriswray]

That rules out the possibility of the CTS circuit having some sort of high-resistance short that would simulate the CTS being hooked up.

Could you also pull the cts and take a lighter to it and should it kick the fan on? I know that sounds crazy but would that essentially simulate that the coolant is up to temp and the fan should kick on right?

[Vigo]

Well if the fans not kicking on with it unplugged (infinite resistance) it wouldnt kick on just from heating up the sensor either because all that does is raise its resistance.

[minigts]

Well if the fans not kicking on with it unplugged (infinite resistance) it wouldnt kick on just from heating up the sensor either because all that does is raise its resistance.

Yeah that's the kicker, why isn't it coming on when it's pulled. :-\

Joe, the red piece will come out of the plug and then there is a release for the pin. Aside from unwrapping the wires from the CTS area to the plug, I just can't imagine what is causing the issue. If you guys didn't unwrap that area from the lower harness up to the plug, that would be my next suggestion. I know the CTS wires are tied into the harness in a couple of places and since we checked the wires to the SMEC, that would be the last thing to check, in my opinion. It has to be something simple we're overlooking.

Vigo, you coming to SDAC? :) Franzen is coming, btw.

[Vigo]

I want to, but i'm going to Canada the next weekend so i'm iffy on over committing myself in time and money. I dont think SDAC is ever going to get any closer to me than this, though!

[cordes]

Yeah that's the kicker, why isn't it coming on when it's pulled. :-\

Joe, the red piece will come out of the plug and then there is a release for the pin. Aside from unwrapping the wires from the CTS area to the plug, I just can't imagine what is causing the issue. If you guys didn't unwrap that area from the lower harness up to the plug, that would be my next suggestion. I know the CTS wires are tied into the harness in a couple of places and since we checked the wires to the SMEC, that would be the last thing to check, in my opinion. It has to be something simple we're overlooking.

Vigo, you coming to SDAC? :) Franzen is coming, btw.

https://cdn.meme.am/instances/42723055.jpg

[wheming]

I want to, but i'm going to Canada the next weekend so i'm iffy on over committing myself in time and money. I dont think SDAC is ever going to get any closer to me than this, though!

Well, then that's decided then. Now you are obliged to come!
Be sure to find me, so i can say hi.

[Vigo]

I'll see if i can rope someone into keeping me company for the trip.

[james]

by any chance is it csx-t 315?

[82 Rampage]

Made good progress this evening, got the radiator mounted and the fan works as it should now. The problem was that the speed sensor was unplugged for some crazy reason.

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[Vigo]

Never heard that one before! I'm pretty sure i've had numerous non-working speed sensors in my vehicles and im pretty sure SOME of them were unplugged and i never had this problem. But thanks for the update!

[mrchriswray]

by any chance is it csx-t 315?

this one is csx-t number 303.