gmachinz

The Volvo relays are a pretty stout assembly-rated @ 40A continuous and yes they are 2-speed however, the Mark VIII fans are not a 2-speed fan-the middle terminal is a dummy terminal. If you trace the wiring about 3 feet from the plug you'll see that I side the loom itself the middle wire is cut and taped up. Ford used a primitive type of VSF (variable speed fan) module to step up/down fan speeds based on certain engine criteria such as vss, AC use, coolant temp, etc. The RF24 T-Bird fans ARE dual speed and can be ran by a Volvo relay. The T-Birds used a black plug while Mark VIII fans had white ones. The 2nd design (before Ford discontinued them) Mark VIII fans also received a black plug so identification on the newer ones can be tricky.

Fuse protection for the Mark VIII really depends on how you plan to trigger it. What kind of controller other than a Volvo (which won't work) were you thinking?

dhonnoll

Well That SUX I was told that the Lincoln MarkVii was a 2 speed fan and that was why they were so desireable. Now, this one that I pulled had a yellow wire that someone added to it going somehwere like in the cab or something. I assumed it was a ground and was just going splice it. Do these MarkVii fans pull a lot of air? How can I find out for sure if I have a 2 speed or not? It came with a white plug (wire harness side)

Mod (Ret.)

If it's a two speed fan, there should be three wires (like my Mark Viii fan I'd think); one is ground, one is low speed, the other is high speed.

dhonnoll

3 wires, 1 blue 2 black but according to what I am seeing on google search of fan shroud part number its a variable speed not a 2 speed. So how does this work? Power it on and it comes on full speed?

Mod (Ret.)

Variable speed would indicate to me that a controller is used to vary the current to it. For example, the controller would provide 60% for the A/C activation, or low temp; 100% if the temp rises to a pre-set temperature.

My guess is that the blue wire is the "hot lead, and would connect to the hot lead of a controller. The two black leads would be grounds; one that would get ground for the A/C clutch activation, and one that would get ground from the temp probe/sensor.

Again, just a guess though. On my mark Viii (yep, a true 2 speed), I have three wires; one is black (ground), one is blue and the third is black/red. I think the blue is low and the black/red is high, but I can't remember; I'll have to check my controller wiring to verify which is which.

dhonnoll

Here is what I am thinking. Keep it simple. Since it is a single speed and if I understand it correctly will take positive input from either hot pole and spin the same speed I am thinking input one on the Volvo conteroller trigger "speed 1) which would just be on, then a temp switch in the radiator trigger "speed 2" on the controller which would just be condition 2. Just keep it a single speed fan but with 2 condition inputs. Would that work? I am sure for that 4.2L this fan is more than sufficient.

Mod (Ret.)

If that's how this Mark Vii works, then sure. But first, the person has to identify the blue and two black wire operation.

gmachinz

Simple test is to ground the far lead....then apply power to one lead, then the other-but NOT at the same time-if the speed does not change-its single speed. Lincoln varied the speed using only the high speed + lead and its proprietary VSF control unit. T-Bird were different as were the Crown Vic's. 1993-96 Mark VIII's roughly 4000 cfm. 1997-98 Mark VIII's were about 4500 cfm.

dhonnoll

So again, if I use the Volvo 2 speed controller to not be a 2 speed but rather a 2 condition controller would it work? Will it handle the amount of amps that fan pulls? If I ground a far lead, then make one hot and not the other and later the other hot and not the first will that funtion for my 2 conditions?

gmachinz

Yes....as long as the fan motor is dual speed. And, while the Volvo relay is rated @ 40A, you should still verify max amp draw using an inductive amp probe just to be safe.