Climate control
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Starting Member
Joined: Sep 2019
Posts: 122
We are almost there.
1) jumper 87A to 30 and see if you get whatever fan speed is selected in the truck.
2) Pull the relay and the 30A hvac fuse in the U/H fuse box back out and measure the resistance again with the ohm setting of 200 and measure between relay socket 87 and the fuse socket hole that does not have voltage
1) jumper 87A to 30 and see if you get whatever fan speed is selected in the truck.
2) Pull the relay and the 30A hvac fuse in the U/H fuse box back out and measure the resistance again with the ohm setting of 200 and measure between relay socket 87 and the fuse socket hole that does not have voltage
1...worked on 3 not 4.
2...without jumper? 1
BF Veteran
Joined: Jan 2007
Posts: 4,628
From: Florida
OK good work on debugging the issue. Here’s what we know: The control in the cabin works, The blower and its wiring and ground work. The resistor network works. Not sure if the relay is OK yet but probably is because its new. When you go to fan speed #4 the power comes from a different path which has failed. Somewhere between the 30A HVAC fuse and the relay, there is too much resistance caused by either a frayed or partially broken wire, corrosion, a bad or loose socket terminal, a bad splice connection or a bad connector under the fuse block. The reason why we know this is that you have 12V on 87 at rest but when you put a load on that power circuit with the blower fan the voltage drops to zero due to a very high resistance in that circuit. Start by following the wire cable run from the relay socket to the U/H fuse block by unraveling the wire loom cover and tape and look for corrosion, breaks, exposed wires etc. The power runs on an orange wire. Well go from there. I have an appointment and will be gone for a few hours. Good luck.
BF Veteran
Joined: Jan 2007
Posts: 4,628
From: Florida
Look to see if there is a power terminal block with screw terminals close to the battery to get your power from. If not then you can connect to the battery post. Go to the auto parts store and buy an inline fuse holder and a 30A fuse. Then get the proper length of red 10 gauge wire along with 3 blue heat shrink butt connectors and a ring terminal with the proper stud hole size for your power connection point. On the back of the relay you need to locate the orange wire that is coming from the U/H fuse block and cut it a few inches behind the relay socket. Be careful because there is at least one more orange wire back there. Let me know if you need help locating the proper wire that goes to relay pin 87. Connect your new power wire to the back of the relay socket at the short orange wire stub and tape off the other end of the orange wire from the U/H fuse block. A few zip ties and you should be good.
George
George
BF Veteran
Joined: Jan 2007
Posts: 4,628
From: Florida
I assume that you mean to tap into an unused fuse position. You would have to use the U/H fuse box for that 30A circuit and I've never had that one up to see the underside so I don't know what you would need. Maybe someone else that has pulled that fuse box can give you some guidance.
George
George
