No power to blower motor, no AC no heat

Stereo, security systems, vehicle electronics, and electrical-related discussions
Post Reply
goat69
Posts: 12
Joined: Sat Mar 29, 2014 6:11 am

No power to blower motor, no AC no heat

Post by goat69 »

hey guys.... and gals.. So here's my dilemma. I have no AC and no heat coming out of my vents. The blower motor does not turn on. I've changed the AC blower motor resistor and wire harness as both for fried. I removed and checked the blower motor and did a bench test and it turns on just fine. I then checked the two 10amp fuses under the dash and both checked out fine. Did an ohm test on the relay under the hood and it checked fine. Now what I've noticed is I'm not getting any power to the under dash fuse box, no power to the blower motor and no power found at the relay switch and yes I turned the ignition key to on. HELP! What am I missing?? Thanks all. - Will
User avatar
joatmon
Posts: 10018
Joined: Fri Mar 21, 2003 5:19 am
Location: SMC MD

Re: No power to blower motor, no AC no heat

Post by joatmon »

I saw you post from a couple of years ago said you had a 2006 Vibe

The relay for the blower motor is in a small relay block directly above the glove box. Here's a pic showing the relay block unbolted, and pulled down to show the top (not normally visible), the one marked "Heater" supplies power to the blower motor
P-relays.jpg
P-relays.jpg (54.81 KiB) Viewed 3011 times
Over the course of vibe history, a few people have had the tail relay shown in that pic work loose. So a first step would be to pull the glove box, then reach up on top of that relay block and make sure the relay is fully seated

That Heater relay gets power from the Heater fuse, which is a big 40A block fuse in the under dash fuse panel. If the previous blower motor and wiring harness were fried, that 40A fuse is a probable suspect.
heaterfuse.jpg
heaterfuse.jpg (92 KiB) Viewed 3011 times
Image
goat69
Posts: 12
Joined: Sat Mar 29, 2014 6:11 am

Re: No power to blower motor, no AC no heat

Post by goat69 »

cool... man I sure hope that works will try it out tomorrow Saturday and report back my results . Thank you buddy!
User avatar
joatmon
Posts: 10018
Joined: Fri Mar 21, 2003 5:19 am
Location: SMC MD

Re: No power to blower motor, no AC no heat

Post by joatmon »

I re-read your first and saw this
goat69 wrote: Fri Oct 09, 2020 4:55 pm Now what I've noticed is I'm not getting any power to the under dash fuse box
Are you not getting power to any of the circuits that run through the under dash fuse block, or was it just to the two fuses you checked? If the whole under dash fuse block has no power, then it would be a problem further upstream than what I previously said, but I think you would have posted about a lot of other things instead of just the blower.

I've attached a schematic of the blower circuit for a 1st gen matrix. There are some differences between the vibe and matrix air conditioning systems, but I think the blower motor circuit is the same.

a couple of things to notice from the diagram
The AC fuse only gets power when the heater relay is closed
The coil for the heater relay only gets a ground when the blower speed control switch is not in the off setting
The coil for the heater relay gets 12V from the Gauge fuse, which only gets power when the ignition switch is in run (not ACC)
The blower motor gets 12V from the heater relay.
Ground for the blower motor, comes either directly at the high speed setting, or though various parts of the blower resistor at other speed settings. If the resistor is removed, the blower should still run at the high setting (loss of lower speed settings is good indication of bad resistor)
Attachments
1st gen matrix HVAC blower circuit
1st gen matrix HVAC blower circuit
heaterCircuit.jpg (63.89 KiB) Viewed 2997 times
Image
goat69
Posts: 12
Joined: Sat Mar 29, 2014 6:11 am

Re: No power to blower motor, no AC no heat

Post by goat69 »

Sorry for the delay in getting back to you.. I checked the 40amp fuse and it's good. I'm giving up. Gonna bite the bullet and take it to the shop. ARRGGH...I hate giving away my money when it's probably something so simple that I"m overlooking.
User avatar
joatmon
Posts: 10018
Joined: Fri Mar 21, 2003 5:19 am
Location: SMC MD

Re: No power to blower motor, no AC no heat

Post by joatmon »

continuing this thread instead of the new one at https://forums.genvibe.com/phpBB3/viewt ... 18&t=47743
In that thread, you said
Would a bad heater relay (directly above the glove box) be the cause of no power to the 10amp fuse found by the steering column? I have no power (voltage) going to the 10amp fuse, car on or off, nor am I getting any power to the blower. Before I pull the relay box holding the 3 relays above the glove box, wanted to see if that's a possibility or should I be looking elsewhere for no power. Oh and yes the relay in the engine compartment is good. Thanks.
If the 10A fuse you refer to is the AC fuse, then that's ok if the HEATER relay is not closed.

This diagram shows where there is 12V when the ignition is off. Relative to the blower circuit, it gets to the 100A ALT fuse, the ignition switch, and one side of the ignition relay
I assume all of those are ok, or you would be having a lot of other problems, not just the blower.
12V also gets to and through the Heater fuse, down to the heater relay, but the heater relay is not energized, so it stops there.
The 10A AC fuse is actually grounded at this point
blower-io.jpg
blower-io.jpg (63.04 KiB) Viewed 2787 times

-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
This diagram shows where the same but with the ignition switch set to run (same as when the engine is running, although the engine does not need to actually be running) and the blower speed at OFF
The ignition relay is closed, so now 12V flows through it, powers the GAUGE fuse and gets to the top of the HEATER relay coil. The fan speed is set to off, so the HEATER relay coil is open, not grounded, and the relay says open. The AC fuse is still grounded.
I assume the ignition switch and the GAUGE fuse are ok, or you would be having a lot of other problems
blower-irfo.jpg
blower-irfo.jpg (64.84 KiB) Viewed 2787 times

-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
This diagram shows the same but now fan speed switch set to high
The fan speed switch now sends ground to the HEATER relay coil, the HEATER relay is closed . Now 12V gets to one side of the blower motor and one side of the AC fuse. On speed HIGH, the blower resistor is bypassed and ground is applied to the other side of the blower motor
blower-irfh.jpg
blower-irfh.jpg (66.1 KiB) Viewed 2787 times



-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

So, all that being said, if the fuses are all good and the other source items that would cause other issues are ok, then it seems like the problem could be either the HEATER relay is either bad or loose, or that the fan speed switch is bad or disconnected, or a bad wire somewhere. You said you had to replace the blower resistor wire harness, not sure if that included the wires to the blower motor itself, might be worth checking for a hard ground at the blower motor when the fan speed switch is set to high. If the ignition is off, but the fan speed switch is set to high, you should get a ground on both wires going to the blower motor connector

If you do pull the relay block over the glove box to check out the HEATER relay, there are two obvious bolts that are easy enough to get to, and a third one ludicrously placed on top of the block that bolts it to a horizontal metal pipe. That one is a hassle to get to, and I didn't put it back when I had dropped the relay block. There's also a plastic pin that snaps into the metal pipe, so after you pull the three bolts, it will take some amount of force to pop it free from the pipe
Image
goat69
Posts: 12
Joined: Sat Mar 29, 2014 6:11 am

Re: No power to blower motor, no AC no heat

Post by goat69 »

Thank you joatman.. you're a great asset to this forum!
goat69
Posts: 12
Joined: Sat Mar 29, 2014 6:11 am

Re: No power to blower motor, no AC no heat

Post by goat69 »

Hmmm.. I don't know, but I ordered a new heater relay (the one above the glove box), installed it, turned on the AC and bam it came on. For kicks I put back the old relay and for the life of me I just don't get it. AC and heat now work even with the old relay. I did verify that it wasn't loose earlier but now all seems fine. Mystery to me, but happy I now have AC ready for the summer. Thanks all for your help on this.
Post Reply