How to repair/replace the 2005, 2006, 2007,
2008, 2009 2010 Mustang Bad Hi and Low Speed Fan Relay.
If you have run into a problem with your mustang over heating the problem may be the POOR DESIGN that Ford did for the relay design that controls the cooling fan and its speeds.
Why did this happen: It happens because Ford thought they would save 3 cents and go with a relay and slip connector that is not rated for the amperage that the fan is pulling. Bad Ford!
You could get a new Fuse/Relay panel for under the hood, but my guess is this is going to happen again.
So here is my Fix – a Bosch that is actually rated for 30/40 amps with a connector that is ¼” not 1/16”.
What you will need:
(2) Bosch Relays (spend the extra 2$ and get the real deal.
(2) Relay Sockets (or in my case I got a dual Bosch Relay Socket)
Wire of at least 12 gauge & wire of at least 16 gauge
Red 12 gauge
Green 12 gauge
Red 16 gauge
Blue 16 gauge
Green 16 Gauge
We are going to completely remove the shitty Ford Relays and replace them with a much better Bosch design, that is rated for more amperage and has a terminal that is much stouter.
Here you can see them removed with the damage to the socket. This is thermal damage caused by the terminal that Ford chose to use not being rated for the amperage that needs to flow through the connector. In the case of my car, the low speed did not suffer any damage, but we are just going to move both relays so that I don’t ever have to worry about this again.
This image shows the damage to the Relay Socket Board. You can see from these shot that changing just one of the items: the Relay, the Relay/Fuse Socket Board, or the Wire connector would not have solved the problem as all three are damaged. TOO many connections that are too small FORD. Poor design work!
In the above photo you can see the Relay Control Wires:
The thin Green with Violet Stripe is the Hi Speed control wire (85 on relay Hi Speed) Purple Arrow
The thin Dark Blue is the Lo Speed control wire (85 on relay Lo Speed) Purple Arrow
The 2 Red Wires in one socket are the other side of
the relay control (86 on relays)
Green Arrow
There is no need to cut these wires. Just tap on to them and tape up your work, see below photo:
Green with Violet is the high Speed [Green arrow]
These will need to be cut and butt connected as the picture below shows:
With all those wires connected, you should only have the 12v+ Constant left, shown in the photo below (Green arrow) You will need to put a ring connector on this and connect it to the bolt that you removed in the beginning to disconnect the 12v battery source.