Blowing Blower High Relay

[Hoplite]

Hey Gents,

My truck consistently burns out the blower motor relay (behind glovebox) so that it only has speeds 1-3. Everytime I replace the relay, it typically lasts about a month or so before it goes out again. Has anyone had this issue and fixed it?

Thanks!

Notes on mine:
- I hadn't confirmed it but I'm pretty sure this happens when I leave the fan on high while starting the truck. I don't beleive it's ever done this when the fan wasn't on when starting the truck.
- This has never happened during driving, only seems to stop working (burn out) when starting the truck with fan on high.
- I don't believe it's brand/quality related as I have done AC delco and after market brands with the same effect. I replaced the switch panel on the dash just to be safe and it didn't change anything. (Mine is a 95 so I swapped out to one of the newer (96+) AC declo switch panels that are manufactured for a 95.)
- I do have some sort of grounding issue on the motor that I have never figured out. I eventually ran an individual ground for it to the support "Cross pipe" right above it.

 

[Onizukachan]

Check the two wire connector Near that dash tube support. Mine was bad internally and causing massive current usage, I cut it out and connected the wiring directly.

also make sure the ground tab is connected using a self tapping screw to the mounting plate itself and not stacked onto one of the mounting screws.

 

[Hoplite]

Check the two wire connector Near that dash tube support. Mine was bad internally and causing massive current usage, I cut it out and connected the wiring directly.

also make sure the ground tab is connected using a self tapping screw to the mounting plate itself and not stacked onto one of the mounting screws.

Thank you for sending this. I'll have a look in a bit. To be specific, when you say two wire connector, do you know what this in circuit with? I don't have it in front of me but if I remember right, it's just a single hot wire that goes to the blower.

 

[Onizukachan]

It’s the ground wire for the blower and the power wire for the blower that go thru it.


Look, sort of behind and next to the vent, above the blower wrapped in foam with other harnesses.

sincei did both these I no longer have the fan shutting down when switched to high. I had also installed a new blower motor but discovered the true issue after doing so.

 

[Onizukachan]

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[Orpedcrow]

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Pull the foam rubber cover thingy off of the blower and check the black and purple wire connections also. Make sure the little ground tab is secure and not corroded. Make sure the connections are tight.

 

[Onizukachan]

Great pic @Orpedcrow .
I hope I can explain it better with that visual.
that black ground goes to a “loose” tab that isn’t preinstalled onto the metal blower fan body. should be screwed by itself with a self tapper into a smaller hole next to a mounting hole/screw. Not stacked onto the mounting hole using the mounting holes screw.

that’s what some PO did and which instigated the poor ground connection, resulting in the wiring damage.


that connector on the right is the one that had overheated and let the metal connector inside become loose only making intermittent contact as a result.

 

[Orpedcrow]

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I scratched the black paint off of the blower before installing the brass tab too. Then covered it in diabetic schmoo

 

[Onizukachan]

Dielectric grease… always a good idea.
I smeared it lightly on the back of the tab and head of the selftapper, and made sure the heat shrink crimps we’re full of it when I bypassed that connector.

I forgot that mine was so bad (charred/melty) I wound up cutting the last 4 inches off the blower motor ground cable, putting a new terminal on a piece of 12ga fine strand speaker wire, and then patching that in With a crimp As well. I used dielectric grease on th3 terminal connector, amd made sure it was as tight as I could get it and still get it on to make sure I got maximum connectivity.

 

[Schurkey]

Don't forget to verify the amperage draw of the blower motor.

Very common for the blower motor to pull excess current due to damaged/dry bearings, debris in the squirrel-cage, overheated windings in the motor itself, etc. The excess current draw causes burning of the relay contacts, overheating the wire harness, and so forth.