A/C stops blowing when I come to a stop??

[RaysnCayne]

Hi all,

I had this problem last summer, and after some solid input, a new blower motor seemed to have fixed it back then. https://www.gmsquarebody.com/threads/a-c-only-works-when-driving.43446/

But I'm running into the exact same problem all over again this summer: the cold air (any air) just completely stops coming through the dash vents when I come to a stop (no matter what fan setting I'm on). The A/C compressor/clutch is still doing its thing, just zero cold air coming out the vents inside. I just checked this weekend and it seems like the "new" blower motor is not working - which makes me think there's something else wrong - something causing blower motors to fail prematurely. Would anyone here have any ideas what might cause this?

I guess if replacing a blower motor every June is what it takes to keep my A/C going, that's a sorta small price to pay vs. replacing bigger parts or getting freon topped off. But it seems quite odd a new (hardly-used) blower motor would take a dump that quick.

 

[SquareRoot]

Sounds more like a vacuum issue. First step would be opening the hood (while stopped of course) and see if the blower motor is actually working.

 

[Edelbrock]

To clarify, your saying that the HVAC blower works when you are driving down the road, but then stop working when you come to a stop? Then starts working again when you start driving?

Or are you saying that the A/C stops blowing cold air when at a stop. And the the air from the HVAC gets cold again when you start driving?

Or both?

 

[legopnuematic]

If the blower motor stops/is intermittent, first thing I’d check is the heavy power wire going to the blower motor. The molded connector on the end can get misshapen/shrinks or something where it visually appears to be connected, but it’s actually not seated completely.

My 76 is that way, on occasion it’ll fall off or lose connection. Really need to replace the connector.

Easy enough to check, while running, set the blower on high and wiggle the wire. Should be easy enough to hear if it cuts in and out.

 

[PrairieDrifter]

Assuming air flow stops, is what you mean, sounds like a vacuum issue. I'm guessing 80's truck? There should be a vacuum canister and a check valve on the drivers side under the wiper motor.

Make sure the check valve is working and the tank isn't leaking.

 

[WFO]

Assuming air flow stops, is what you mean, sounds like a vacuum issue. I'm guessing 80's truck? There should be a vacuum canister and a check valve on the drivers side under the wiper motor.

Make sure the check valve is working and the tank isn't leaking.

And not hooked up to ported vacuum.

 

[PrairieDrifter]

And not hooked up to ported vacuum.

That's a great point too! Need manifold vacuum.

He didn't 100% say it was working otherwise, but. Yes ported vacuum would cause this issue.

 

[RaysnCayne]

Thanks all!

Sorry for posting and ghosting. Got busy and then forgot about this post b/c the A/C suddenly works fine again.
Guess it needs a drive or two at the beginning of A/C season to get things loosened up?

To answer the various questions:
1. This is pretty much 100% factory set-up (truck specs are right there in my profile). As far as I know, all A/C vac lines are in place and going where the factory put them in '87. Vacuum ball intact and lines running to a fro. (I'm pretty sure there's a check valve, but not sure if it's 100% functional. I'll have to check on that.)
2. Yes, the A/C works exactly as it should as long as I'm moving/under load, but completely stops blowing any air when I come to a stop.

 

[YakkoWarner]

Thanks all!

Sorry for posting and ghosting. Got busy and then forgot about this post b/c the A/C suddenly works fine again.
Guess it needs a drive or two at the beginning of A/C season to get things loosened up?

To answer the various questions:
1. This is pretty much 100% factory set-up (truck specs are right there in my profile). As far as I know, all A/C vac lines are in place and going where the factory put them in '87. Vacuum ball intact and lines running to a fro. (I'm pretty sure there's a check valve, but not sure if it's 100% functional. I'll have to check on that.)
2. Yes, the A/C works exactly as it should as long as I'm moving/under load, but completely stops blowing any air when I come to a stop.

If the blower is still running but you don't feel any air, check to see if it has shifted to the defogger or floor outlets (or splitting between all 3 which means you don't feel much of anything). I'm guessing a vacuum loss somewhere in the HVAC controls.

 

[Turbo4whl]

Thanks all!

Sorry for posting and ghosting. Got busy and then forgot about this post b/c the A/C suddenly works fine again.
Guess it needs a drive or two at the beginning of A/C season to get things loosened up?

To answer the various questions:
1. This is pretty much 100% factory set-up (truck specs are right there in my profile). As far as I know, all A/C vac lines are in place and going where the factory put them in '87. Vacuum ball intact and lines running to a fro. (I'm pretty sure there's a check valve, but not sure if it's 100% functional. I'll have to check on that.)
2. Yes, the A/C works exactly as it should as long as I'm moving/under load, but completely stops blowing any air when I come to a stop.

On a phone it is hard to see your profile. What year is your truck?