2007 Mustang GT High Speed Fan Not Working

2,697 Views | 6 Replies | Last: 5 yr ago by TexasRebel
aggieforester05
How long do you want to ignore this user?
AG
2007 Mustang GT/CS, 4.6L 3V, 5 speed manual, with 117K, Vortech supercharger (air/water intercooler)

My high speed engine cooling fan is not working. I don't drive this car very often for more than around town errands. I've been chasing a custom tune for my truck for 2.5 months and the last part of a long story is that I've had to send the ECU into SCT to be scanned. So my truck has been dead in the water for the last few days. So I'm currently driving the Mustang to work which is an hour each way by the time I drop off/pickup my daughter from school.

Today on the way to pick her up I did a second to third gear pull on the interstate exit ramp. I've been monitoring engine coolant temps and IAT temps on the car via OBD2 fusion. After the interstate pulls, the engine coolant temps started to creep up. (IATs on this car stay near ambient temperature as long as I'm moving. They only go over 100 degrees if I'm sitting stationary.) The engine coolant temps will not go over 196 when idling and the low speed fan is on. Cruising, I typically see 200 - 208 degrees. After the pull the temps went up to 215 pretty quickly, then slowly creeped up to 228 over the next five minutes or so. After another five I got to the school and the temps were back down to 217. When I left the school, I set at a redlight and they went up to 233. I turned the heater on and cruised between 40 - 55 most of the way home and got them back down to 213. Then I hit slow residential roads and by the time I got in my driveway it was up to 244 (factory temp gauge was almost in red as well). Before I shut it off I got out to look at the fan and it was stationary.

I let it cool awhile and then started it back up and the low speed fan came on and it wouldn't go over 196 degrees.

So my thoughts are that the car is fine until driven hard and the engine temps go up. Then the fan dies completely and it won't cool down.

I looked up the fuses and relays in the owners manual and the pin outs of the relays in my Chilton's manual. I checked the high speed and low speed relays and the starter relay which were all the same part number. The impedance matched on all three and I even swapped the starter relay and high speed fan relay. The starter still worked fine afterward. The fuse was good as well. I'd suspect a wiring or mechanical issue with the fan would cause a low speed issue as well. If there were a problem in the coolant loop, I'd expect the car to overheat while idling or regular driving.

The car has a Vortech H.O. supercharger system installed by me and a custom tune done by Brenspeed. I'm going to call them tomorrow to verify that it's not a tune issue, but it's been running this same tune for almost 4 years with no issues. I do know that the Brenspeed tunes typically turn the fans on at lower temps than stock due to the aggressive timing. I've had zero issues with this car in that time period and the 12K miles since the system was installed, other than the battery.

Any other ideas what the problem could be? I don't need two vehicles down at once! Thanks
TexasRebel
How long do you want to ignore this user?
AG
Fan windings?
Bad brushes?
aggieforester05
How long do you want to ignore this user?
AG
That wouldn't explain why it works fine in the low speed temp range and is completely dead after it hits the high speed temp threshold.
TexasRebel
How long do you want to ignore this user?
AG
Different brushes/windings kick up to high speed.

1agswitchin4lanes
How long do you want to ignore this user?
AG
Did you also check the relay that's mounted on/in the fan shroud at the plug. This is usually the culprit with most fan problems on the 05-09s.

Also, have you used a multimeter and checked voltage at the fan harness at lower temps and then at higher temps?

I've seen cases where at like 180 there's 12V and when the temp creeps up to 195-200, the voltage drops to 2 or 3. If you have this issue, you need to go back and look at the relays and wiring. Pull the relays out and look at the pins in the fuse/relay box and make sure none of them are burned. Sometimes the green/violet wire on the high speed relay (30A) position will burn up.
TexAg1987
How long do you want to ignore this user?
aggieforester05
How long do you want to ignore this user?
AG
Thanks guys, I'm going to do that trouble shooting soon. After some frustration with Fedex I managed to get my ECU for my truck back this AM, so I'm not sweating the Mustang problem for the moment. I did try to just baby the car around this morning and it was doing okay until I got it on the highway, then they started to creep to about 217. I went back to town and surprisingly got it to cool down when I hit city traffic. Got the ECU and parked it for now.
TexasRebel
How long do you want to ignore this user?
AG
Interesting...

The fans don't do anything at highway speed.
Refresh
Page 1 of 1
 
×
subscribe Verify your student status
See Subscription Benefits
Trial only available to users who have never subscribed or participated in a previous trial.