Question
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Followup To
Question -
The blower has quit working on high. It was intermittant on high now its dead but only on high - its works on all the lower speeds. I have a generic wiring diagram for 88-00 suburbans and have replaced the switch and the relay but still have same problem. I can feel the relay energize so i know the switch is switching 12v to energize the relay and this removes the res network and is supposed to apply the 50A 12v directly to the fan. I pulled the relay out and can measure 12v coming from the 50A source and I tried to jumper this to the fan wire and the voltage drops to 0 and nothing happens. Also the fuse does not blow so its not shorted. Does the 12v go somewhere else after the 50A fuse before it gets to the relay? I can jumper the resistor source voltage to the same fan wire and it blows which is the same as using the switch on lower speeds. Any ideas?
Answer -
Hi DM,
You seem to have a very good grasp of that circuit.
"I can jumper the resistor source voltage to the same fan wire and it blows which is the same as using the switch on lower speeds." I don't know exactly what you mean there. Where did you jump to?
Have you tried jumping directly from the battery Pos post, to the blower motor? Try it while Hi is selected.
You say "I pulled the relay out and can measure 12v coming from the 50A source and I tried to jumper this to the fan wire and the voltage drops to 0 and nothing happens."
That voltage, if I am not mistaken, comes directly from the battery, so should not drop to zero. Have you swapped fuses, and checked to be sure the fuse is making good contact? Sure there is not a fusible link to that wire? If so, it could be blown, yet the wire coating still look good. While measuring for voltage at that hi relay supply connector, strech the fusible links a little to see if the reading drops.
Seems in the back of my mind that the last time I looked at the circuit diagram for that truck, there are two relays, and both must be closed for Hi, but don't hold me to that..
Van
I jumpered from the red wire at the relay (50A source) to the purple wire at the relay (blower wire).
I have not tried to jumper directly from the batt to the blower yet (High select will not matter doing this)
The fuse checks good with an ohm meter and I have 12v on both sides of the fuse even when the switch is on high.
not sure about a fusable link - I suspect something is wrong between the fuse and the relay since I have 12V at the fuse and 12v then 0V at the relay when swithcing to high.
I'm thinking of trying to open the distribution box under the hood so I can see the connections under the 50A fuse. Not sure how this opens though.
If there is a fusable link where would it be?
Only one relay on a 99. Earlier models had 2.
I won't work on this again until Saturday morning.
AnswerHello DM,
I saw in the GM forum where you got it fixed. Those connections in plastic generally hold ok. It is when the metal connectors get a little loose that heat develops, and melts the plastic.
I have seen fuel pumps do that inside the tank, and on older Dodge pickups, the amp meter in the instrument cluster used the plastic housing as one of the squeeze points for the wire connections. Those studs would carry 85 to 100 amps, and as they got hot, they got looser, then hotter, etc. For sure not a good design, but it was cheap, and worked fine when the battery and everything else was new and tight.
Fixitfox33 and Van, by the way, are one and the same.
Van
