So I built my own Fan Relay module...

E

eduncan911

Registered
Fyi, I purchased this car in 2001 with a broke motor. Come to find out when I got it running last year, with insurance, that it has had $9000 in damage!!! CarFax rules, but jez... There are some tail-tail signs, but it was fixed at a Lincoln dealership. So I know it was fixed as best as it could be (it's great).

Ok, my cooling fan stopped working over the winter and I didn't notice it until things got a little warming a few months ago. Car kept getting close to overheating. Saw immediately that the fan wasn't working (explains why the A/C was INOP as well).

A little debugging, I saw no power was being supplied to the fan with the MAX A/C setting set (which should kick any Ford/Lincoln cooling fan on HS or high speed). Saw I had voltage out of the fuse. Only logical conclusion? Bad VCRM (other EVTMs I've used at the dealship calls it an IRCM or CCRM, hehe.. yet a 3rd definition!).

So I orderd the $230 or so piece and installed it. BAM, cooling fan started working again. But I noticed a weird sound and the fan wasn't blowing as hard as one would expect. Ok, may need another motor soon.

While I was doing this, I noticed the cooling fan motor was been replaced with some type of aftermarket one. To make things worse, there was no connector location on the new motor. Just a 3-wire plug (fyi, only two wires are used on these motors. The VCRM controls the speed of the fan with resistors on that one wire). So whoever put this motor in, spliced into the factory 10-AWG wires!! Argh.


Well, two weeks later I notice the car starting to overheat again. Checking, the damn cooling fan isn't working again!

A bit more involved disassembly of the system reveals that the 10-AWG wire coming from the VCRM can't carry the amps that the fan is trying to draw, therefore creating a high load and burned out the VCRM again. Not high enough to blow the fuse, but high enough it seems to kill the VCRM.

I tried replacing the 10-AWG from the VCRM to the fan, still an unusally high draw. Not to mention I am not goign to get ANOTHER VCRM. Most likely the issue is in the harness from the engine compartiment fuse block to the VCRM for the cooling fan. I didn't not fill like yanking that out and replacing it.


So screw it. I found some 30AMP relays (not high for the fan, as it says up to 40AMPs can draw on the motor). So I wired them in paraelle to distribute the load, ran new 10-AWG gauges, and wired the control circuit up to the EEC power (so when the computer is powered, the fan is on HS).

Figured this isn't hurting anything, since the stock thermostat is 195 degrees or so. Wanted to use the Cold Engine Lockout Switch to pwoer the fan only when the motor is warmed up. But in order to have the A/C working (i.e. defrost), you have to have that cooling fan working if you are trying the compressor. Else the high-side can get extremely high in pressure.


Fun fun...
 
RE: So I built my own Fan Relay module...

That looks cool.

But we can't use that for our fans.

There has to be an A/C override input, so when the A/C is on the fan is on HS at all times (that is normal operation for any vehicle, kick the A/C on and the fan goes to HS... No matter how hot or cold outside it is).

Yes, there's an A/C input but the EVTM doesn't show any solid "A/C Is On" circuit. Only a clutch monitoring circuit, which cycles on/off as the clutch is energized/de-energized.

So without an exact A/C source, we can't really use that. I thought about wiring up the blower motor circuit for something like (another doo-dad I thought of making up). But technically that still wouldn't be accurate.

Ford needs a dedicated circuit that is powered when A/C is on, that we can tap into. Right now, whenever you want A/C (Automatic, MAX, Def, etc) the EATC signals the VCRM to turn on the fan. I found that circuit, it's just a ground (which I thought about tapping into as well until I found it's resistor sensative for EATC diagnoising, and I've been down that path WAAY too many times at a dealership.. You leave those alone).


About the motor, it's not the motor drawing too much current (measured at 32AMPs with the new 10 AWG wiring). It's the extra resistance in the stock wiring to the VCRM that's causing more-then-normal load. Which is burning out the VCRM.

Running my own dedicated circuit resolved the issue, and the fan blows up to normal high speed now (was only blowing about 1/2 speed with a full 13V with the stock wiring, and sounded sick). Now that sucker is moving some serious air, and drawing less current. Hence, it's a wiring issue not a motor issue.
 
RE: So I built my own Fan Relay module...

No, the fan STARTS at 1/2 voltage through the VCRM with the AC on.

When I installed a cooling fan bypass for the track, I measured right at 20 amps with the fan motor on high. I'm still suspect of the motor by what you describe. BTW, the VCRM has two wire feeds for the fan for current carrying capacity. I can understand the 32 amp load taking out the VCRM. What current is it running with your dedicated circuit? Are you using the same ground?

I plan to install the controller as part of the over-ride circuit. The way it is now, I hit a switch and force the fan on high speed through a relay bypassing the VCRM. When the car is down to the temperature I want, I simply flip the switch off and the VCRM takes over. With the controller, I plan to basically switch from the VCRM for the street to the programmable controller for the track. }(
 
RE: So I built my own Fan Relay module...

I don't think it is suppose to be 1/2 voltage with A/C on.

I was the Drivability, Electrical and A/C tech at a dealership and the vehicles I tested, when they had a cooling issue, I hit the Max A/C to get full rpms out of the cooling fan. Never worked on a Mark8 before though.

As a matter of fact, my Cobra (the one in the sig ;) ) kicked the fan on high. I know this by my programming the ECU myself, and noticing when the A/C kicks on the speed of the fan (by sound).

Perhaps the Mark VIIIs are different.

No, not using the same ground. All new wiring. It's an aftermarket fan.

New fan @ Autostone: $95 + tax (Tennessee tax is 9.25%!)
New fan @ Dealership: *gulp*

Price of relays, wiring, and supplies for current bypass: $7 (I had everything, including a box of relays).


Hey the temp doesn't move beyond "O" now, which is about 197 degrees from TwEECer's temp reading.

Heat will still work fine as the thermostat doesn't open until 195 or so.

Only annoyance is the sound of the fan on HS at all times. But it's why we have double sealed doors and thick insulation.. So we don't hear it in the car.


Half-speed may work, but I'm not taking any chances. And I've already blown $240 or so on a VCRM that is burned out again.

To hell with it. When the twin turbos go in with the built motor, I don't expect to be using the stock ECU setup anyhoot.
 
RE: So I built my own Fan Relay module...

[div class="dcquote"][strong]Quote[/strong]
I don't think it is suppose to be 1/2 voltage with A/C on.I was the Drivability, Electrical and A/C tech at a dealership and the vehicles I tested, when they had a cooling issue, I hit the Max A/C to get full rpms out of the cooling fan. Never worked on a Mark8 before though.As a matter of fact, my Cobra (the one in the sig ;) ) kicked the fan on high. I know this by my programming the ECU myself, and noticing when the A/C kicks on the speed of the fan (by sound).Perhaps the Mark VIIIs are different.[/div]

They are different. The manual even states so. They start at 1/2 speed with the AC on. Even w/o the AC, stock programming kicks the fan on (low 1/2 speed) at 215 degrees and it shuts back off at 205 degrees. And of course they shut off at 45 mph. The MAX AC trick does verify the fan motor condition however.
 
RE: So I built my own Fan Relay module...

[div class="dcquote"][strong]Quote[/strong]They are different. The manual even states so. They start at 1/2 speed with the AC on. Even w/o the AC, stock programming kicks the fan on (low 1/2 speed) at 215 degrees and it shuts back off at 205 degrees. And of course they shut off at 45 mph. The MAX AC trick does verify the fan motor condition however.
[/div]Yep, that's normal operation for the vehicles I was talking about. You were just much more clear in describing it.

I never found the memory addresses in the binary to adjust the cooling fans, as my Cobra I programmed 188/180 (on/off) for LS and 195/180 (on/off) for HS.

Well, whenever this vehicle gets a serious overhaul I may get yet "another" VCRM and another fan. For now, it's ok.

Something else I noticed during the overheating... Even driving 65mph didn't keep the car cool enough (the temp would creep up if I drop 65mph for a long drive). I had the best expereiences over 75mph, where it finally kept the car cool enough. Restriction of airflow I suppose.

Yep, my fan is running HS even at 100mph. :( I may put on a speed switch I have left over from a GM vehicle. Cut the fan off at 75mph or something.
 
RE: So I built my own Fan Relay module...

[div class="dcquote"][strong]Quote[/strong]
...Something else I noticed during the overheating... Even driving 65mph didn't keep the car cool enough (the temp would creep up if I drop 65mph for a long drive). I had the best expereiences over 75mph, where it finally kept the car cool enough. Restriction of airflow I suppose. Yep, my fan is running HS even at 100mph. :( I may put on a speed switch I have left over from a GM vehicle. Cut the fan off at 75mph or something.
[/div]

I have seen cases where electric fans actually do impede highway cooling(aftermarket replacements). I always surmised that's why the Mark VIII(and others) had a speed limit where the cooling fan shut down. I initially worried about airflow with a set of driving lamps behind the grill, but highway tests proved otherwise on my '93.
 
RE: So I built my own Fan Relay module...

"High speed Test" lol

Btw, I really wanted to make sure things were nice and solid. So on my way home lastnight from about 35 miles away, there's a LOOONG stretch of freeway about 4 lanes wide, and fairly flat.

I was on it hard, around 120 to 130 most of the time.

[kill story]
I also came up in traffic and darted around this early 90's model LT1 Camaro with the t-tops off. I guess he decided that he was better then I, and started riding my ass.

Traffic opened up and I gunned it (yes, with A/C on which the WOT switch kicks off). I wanted to know if I had any "performance" issues with that HS fan on all the time and the A/C system heat soaked.

I guess he was an auto.

I guess he didn't realize he had to be on it hard (no easying in) to catch me.

He was up there around 125mph or so, but never caught my speed (kept fading) and never caught up to me later down the road a few more miles.

Only after I got off on my exit (3 miles later), I was caught at a light and waited.. and waited.. and waited... Light turned green and lord and behold, here comes that Camaro flying down the exit ramp!

At the next light he signals for me to roll down my window, I do. He says, "What in the hell do you have in that thing?! And how fast did you get it up to?! I couldn't keep up!" LOL
[/kill story]

Looking down at the temp, didn't budge past that letter "O". LOL So no, no cooling issues here and the 'driving miss daisy' strategy was fine with A/C in the heat. Last night with the "Smokey and the Bandit" driving, it didn't flinch either.
 
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