Cooling Fan STILL doesn't turn on at temp

[Chythar]

As you guys may remember, I had another thread troubleshooting my cooling fan. That problem turned out to be shorted wires. However, even though the fuse no longer pops I never did test the fan again. Well, after swapping the dizzy to solve another problem, I decided to let the Stang idle and see if the fan turned on. STILL no luck.

I had an Autoxray code reader hooked up and reading the PIDs; the ECT temperature slowly rose up over several minutes to 208*, and the fan never turned on. I shut the engine off at about 208.5*. A KOEO test does turn the low and high speed fans on, so the computer does have access to the fan and the fan does work at both speeds. My A/C system is discharged so I don't think turning on the A/C will activate the fan.

I'm at a bit of a loss as to what to check. Ideas? This is the last thing to fix on the Cobra clone before I can get it inspected and back on the road.

 

[HISSIN50]

At 208+, does CCRM Pin 14 show 12 volts?

 

[Chythar]

Don't know yet, will have to check. Might be a couple of days before I can. Anything else I can check while the car is warmed up? I should note that neither the low-speed or the high-speed fan turns on either. What are the stock temp settings for the fan again? I forget if 208* on/200* off is for low speed or high speed.

 

[HISSIN50]

Don't know yet, will have to check. Might be a couple of days before I can. Anything else I can check while the car is warmed up? I should note that neither the low-speed or the high-speed fan turns on either. What are the stock temp settings for the fan again? I forget if 208* on/200* off is for low speed or high speed.

You're right for low speed.

High won't come on naturally till about 226* and you probably haven't let it get that hot. When high kicks on, CCRM Pin 14 goes cold and Pin 17 shows continuity to ground.

Dealing with only low for right now:
If Pin 14 shows 12 volts, check CCRM Pins 1 and 2 for 12 volts. If you have that, the issue is between the CCRM and fan.

 

[Chythar]

Oh Hissin, got a quick question. when checking Pin 14, the positive lead on my voltmeter obviously goes on Pin 14. I'm guessing I'll need to stick a pin in the wire for pin 14 to get a connection. For the negative lead, do I connect it to a known ground, or should I test it differently? I feel foolish not knowing what should be simple.

 

[HISSIN50]

You've got it Matt. Just ground the neg lead. I ground mine either on the engine or a bolt at the front clip. If using the engine, watch that you dont get the lead tangled in the alternator, etc.

A safety pin works well for getting through the wiring insulation. If you wrap electrical tape around the pin, sans the very tip and the curved end (so you can put your meter lead on the pin), it helps prevent a short if the pin moves around.

 

[Chythar]

Alright, finally got off my lazy @$$ and ran the test. Pin 14 (dark blue wire) never sees 12 volts at 208* - I get a steady 0.015v (effectively nothing). To double-check my connections (and for my own curiosity), I checked pin 14 during a KOEO test. Pin 14 showed 12v (11.54v, actually) when the low-speed fan turned on and cut out when the high-speed fan kicked in. I believe pin 17 shows continuity to ground when the high-speed fan is on, but that's not really relevant right now.

So, now what? The KOEO test tells me that the wire leading to pin 14 is good and the computer can control the fan. But the computer is not triggering it at 208*. My Autoxray code reader is reading the ECT PID and showing the proper temperature reading as far as I know - I have a laser temp reader, I can always verify the temperature. Is it possible the computer bad? There isn't a chip in the J4J1 computer, but I can always borrow the Moates chip in my green GT, load in a J4J1 program and set the fan settings lower.

 

[HISSIN50]

You might be right about the PCM being at fault. I've seen similar issues where a speed would not activate at a given threshold but could otherwise be commanded to work.

If you do have a spare Moates chip (sounds like you don't), then I'd just do a burn - treat it like a one speed fan, and get the high speed setting down to like on/off 195/187, respectively (for a balanced 180 stat).

 

[Chythar]

I don't have a spare, but the green GT is not being driven - I can pull the chip easily. I've been looking for an excuse to modify the GT's program, so I have one now.

 

[Chythar]

How very interesting. I just opened up a J4J1 definition in EEC Editor, and it reads the low-speed fan on/off at 216*/212*. The high-speed is 228*/220*. Looking at a standard UP40 definition shows low-speed on/off at 208*/204*, but high-speed is also 228*/220*.

Looks like I need to wait until 216* to test.

 

[HISSIN50]

Sorry Matt, I totally missed the Cobra tune. You are right - low speed on a Snake is 216/212. High speed is the same for GT's and Snakes.

A Moates chip was 70 bucks when I got mine. For like 35 and some shipping, you can get a module that lowers the fan thresholds by like 15*F (to accomodate a drop from a 195* stat to a 180* stat). I havent used the latter though. I think I'd rather have a nice tune on the Snake anyhow however.

Sorry again. I had GT on the brain.

 

[Chythar]

SOLVED

As this is a Cobra conversion, the low-speed threshold is 216*, off at 210*; not the 208*/204* I was testing against. The low-speed fan DOES turn on at 216* and off at 210*. I let the Stang idle for a while longer, and the fan cycled on and off several times at the right temperature. In the end, there was no problem with the system; just the wrong testing parameters.

No worries Hissin, we're all used to working with the GT parameters. I'm just glad it was something simple.

So the fix for the original problem (from the last thread) fixed the issue - just shorted wiring. That's quite a relief.

I bought the Moates chip plus the new Jaybird for the GT to burn the chip myself. This was to correct the shift points for the 4R70W gearset, and I lowered the fan temps too. So I know exactly what you are talking about. Maybe I'll pick one up soon, but not now. I'm just happy the Cobra clone is running properly.