Climate control blower motor resister/wiring & Vacuum Leak

cal74 · Jun 10, 2018

Just got done tearing down a 99 Mazda B3000 (3.0) (Heads & Gaskets)

Picked this up as a flipper, prior to tearing it down the climate control fan would only work on high and also only in the defrost setting.

I replaced the fan blower motor/resister and the wiring and didn't see any obvious vacuum leaks while tearing it down or putting it back together. Didn't scour the lines, but looked them over fairly decent.

Finally got it back together and the fan is still only working on high and only on defrost.

New wire harness is black, yellow, green, orange/black

Existing wires are red, yellow/red, white/green, and orange/black

I hocked the black to the red, green to the white/green, yellow to the yellow/red, and orange/black to the same.

Something wrong here?

And in regards to the vacuum leak, any ideas? I looked behind the glove box and didn't see anything there. Is there a typical place to look when it's stuck on defrost?

Thanks for any/all help

ericbphoto · Jun 10, 2018

Have you looked at the actual control panel to make sure everything is working there? Defrost is usually the default mode of operation because it's the most important function.

Sent from my SM-G960U using Tapatalk

cal74 · Jun 11, 2018

I looked behind the panel and everything appeared to be in good condition and intact.

ForTheLoveOfMonkeys · Jun 11, 2018

It's the blower motor resistor almost for sure, not likely a vacuum leak. You can check the little black "vacuum ball" underneath the coolant reservoir if you want to be certain.

Odds are good you have either a bad/incomplete connection either from the new splices or you also might want to double check to make sure the harness is seated fully and that the resistor itself is functioning properly, I got a non-OEM part and apparently it's a mixed bag with those across vendors for this part so you may have received a defective one.

I'll look today after work to see if my wiring colors match yours.

cal74 · Jun 11, 2018

Thanks Monkey's

I ordered a new resistor today, hopefully it's here by the end of the week and I can check the ball and replace/retry a different resister.

Let me know about the wires when you're able, thanks

ForTheLoveOfMonkeys · Jun 12, 2018

So mea culpa here... :icon_surprised:

I definitely misread your original post, and I will never again post before 8am when I've had my coffee. The symptoms you're exhibiting, the defrost only, are actually classic signs of vacuum leak. With resistor issues you get only "high speed" setting vs. the "defrost only" so counter to my original post, you need to be looking for a vacuum leak/block.

The most common culprits for this on the 3.0s that I've seen (granted I've never worked on anything older than a 1990) are the black ball I mentioned, as well as the two 'plastic-y' lines that come out of it, one to the back near where the blower resistor is and one that winds back along the passenger side exhaust manifold and behind the engine to somewhere in the intake manifold.

These two lines are where you should start. Trace the shorter one from the black ball to by the blower resistor, feel for any irregularities and don't be afraid to gently bend it a little to see if anything pops loose that otherwise looks good. Take a long look at the interconnections between lines.

If that one passes visual and tactile inspection do the same for the other line (in my truck it's red).

If both come up fine, then look at the black ball beneath the reservoir. Check for cracks or rattles.

If all those check out, then you're looking at a smoke test, see if it's coming out from under the dash or in the engine to help narrow the search. It's easy to perform but I can walk you through a cheap DIY version if it comes to it.

When I experienced this it was not long after I changed my own blower resistor and changed the heads. When I connected everything back up I must not have paid enough attention to where the red vacuum line was and it wound up resting against the passenger side exhaust manifold. Oddly enough this didn't cause a leak, so it passed visual and tactile inspection and the smoke test. Wasn't until I look really closely at one of the interconnects that I saw that it had melted internally causing a blockage. Snipped it out, replaced the interconnect with some small tubing I had on hand, shrink wrapped it well and it's been good for the past 4 months.

Again, I'm sorry I may have lead you astray initially and if you're ever in Baltimore I owe you a beer, but this should hopefully help you get to the bottom of it.

cal74 · Jun 12, 2018

Too muggy out right now, but will start digging around and post what I find out.

New resister should be here this week to swap out the one I just replaced.

cal74 · Jun 13, 2018

Resister was wired incorrectly - Advance auto parts wire/colors were completely off. So that issue is solved.

Took the inner fender off last night, two connections were pretty dry rotted. One on the ball and another on one of the T's. Picked up some replacement line, crossed my fingers and still stuck on defrost. Lines going to hubs aren't the best looking, but don't see anything else obvious and have gone over them fairly well.

I'll pull the HVAC panel later and take a look behind, but from the glove box on they look decent.

cal74 · Jun 13, 2018

Not sure how much of a vacuum pressure I should hear, but the line coming off the ball is blowing and there's a noticeable hiss when disconnected.

Bypassed the line going to the hubs to eliminate that and straight to the line going through the firewall. No change...

There's a tiny bit of pressure when you go to recirculate and given enough time the recirc door will open part way, or if you open it there's enough pressure to keep it open.

Following the black line, there's nothing noticeable wrong.

At a loss, want to get this thing listed but it's kind of driving me nuts.

ForTheLoveOfMonkeys · Jun 14, 2018

At this point I'd suggest smoking it out. Remove the air intake hose coming off the MAF, plug up your throttle body with a glove, condom, or something similar and a rubber band. Get a source for smoke, I built myself a DIY smoker using a bike pump a tupperware container and a vape pen from a gas station works pretty reliably, but a really cheap cigar and a good set of lungs could work. Blow smoke into the vacuum line coming off the brake booster and see where it's coming out. If there are no blockages then it should come out wherever the leak is happening, if not visible from the engine bay then it might be under the dash. If still no dice then you've likely got a block somewhere, probably near a heat source that melted the plastic line.

If the defrost was working well before your repairs, then I'd also suggest taking a look at the connections going through the firewall where you swapped out the blower. Another thing was once I fixed my line it still took about a minute for it to build up enough pressure to divert back from the default position on high settings.

You gotta narrow down the search or you'll drive yourself nuts checking every single vacuum line, not sure about how many of those are on you your year's but on the 98, 99, 2003, I've worked on there's been a lot.

fixizin · Jun 17, 2018

D'oh!...

Related: WHERE do you buy these replacement vac lines? Mine are dry-rotting to uselessness... also need the larger ones that run to the PVHubs... NEVER see them listed on parts sites... asked once at a NAPA, was shown some bulk by-the-foot examples that didn't even look close... :icon_confused:

Denisefwd93 · Jun 17, 2018

fixizin said:
Related: WHERE do you buy these replacement vac lines? Mine are dry-rotting to uselessness... also need the larger ones that run to the PVHubs... NEVER see them listed on parts sites... asked once at a NAPA, was shown some bulk by-the-foot examples that didn't even look close...

Yes you want to use a roll of tubing and fittings made by Dorman who markets through almost all the automotive supply houses and chain stores.

looking for form-fitted original equipment vacuum tubing like that would mean going to a yard or possibly a dealership.

The same hard plastic tubing setups are used on other vehicle engines and trust me they can be even more complicated than they are on the Ranger

Climate control blower motor resister/wiring & Vacuum Leak

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