Quick AC question

txredgt · Jun 18, 2011

Driving home from work today and I had the ac on. I usually just cruize windows down but just washing and polishing the windows I would like to keep them as streakfree as posible, but going up a large steady climb uphill the AC stopped working. After going back to flat ground it turned back on but I am thinking this had to do with a vaccum of some sort? Is it common for it to shut off completely? No air was moving through, hot or cold, but after getting to normal again it was blowing cold air again. Any thoughts?

I have always wondered if every vaccum line was 100% good but being a 10 yr old car I kind of expect it not be. Any things to check?

BlownFiveLiter · Jun 18, 2011

It was probably something related to the throttle position. At WOT the ac will turn off, so for whatever reason it may have triggered the WOT relay.

Skud · Jun 18, 2011

StangGT1995 said:
It was probably something related to the throttle position. At WOT the ac will turn off, so for whatever reason it may have triggered the WOT relay.

Exactly.. I'm pretty sure it will also go off when the car is in "lugging mode".

Riley

BULLITT5228 · Jun 19, 2011

I thought that would only shut the compressor down not the blower motor as well?

wmburns · Jun 19, 2011

+1 on above.

The PCM does not have the circuits needed to turn off the passenger compartment blower.

The PCM does have control of the AC clutch. During WOT, the PCM will turn off the compressor.

For the blower to quit working, there is a loose connection someone. Either in the mode control switch, blower motor itself, or grounding.

The blower is grounded via ground G204. G204 is located behind the center console and it's shared with multiple devices including the radio. G204 is frequently messed up during a radio install.

txredgt · Jun 19, 2011

So is this something that I should be concerned about? Its the 1st time I have seen this problem. Should I start by checking the ground?

Skud · Jun 19, 2011

BULLITT5228 said:
I thought that would only shut the compressor down not the blower motor as well?

Sorry, I misread. It's definitely not normal that the blower quits. The A/C compressor will though during WOT and lugging.

Riley

txredgt · Jun 19, 2011

Thanks for the responses.. I thought it was strange that nothing was blowing at all but I also find it strange that it has only done it in 1 instance so far and it was with a load on the engine. Could be worse, my mom's old chevy product which had the dual climate zone feature in the front, randomly the driver side would blow HOT air and the passenger was still on AC. That was crazy to experience and we never did get it fixed since it was random.

Skud · Jun 19, 2011

Quick question:

Does the blower actually stop blowing? Or does it change from coming out of the dash vents to the floor vents? I ask because that is controlled by vacuum..

Riley

txredgt · Jun 19, 2011

Skud said:
Quick question:

Does the blower actually stop blowing? Or does it change from coming out of the dash vents to the floor vents? I ask because that is controlled by vacuum..

Riley

What I remember was that it stopped blowing. I don't really know if it was blowing on the floor vents because it didn't lsat very long and I was coming back from work so I had pants and not shorts on.. I take that drive everyday that I work so I am going to try to replicate it so that I know what is going on, hopefully that works.

Steve491 · Jun 22, 2011

I had a similar problem with my F150. When I went up a hill (low vacuum) it seemd that the blower quit working because you couldn't feel cold air anymore. Turns out it was a vacuum problem with the HVAC dampers and by default, meaning no vacuum, all the air would come out the defroster ducts. When I let off the gas cold air would come out the dash again. It was a quick fix. A small plastic line to the recirculating damper under the hood had deteriorated and fell apart. I spliced a piece of rubber line in and it's been working fine ever since.

wmburns · Jun 22, 2011

Hey Steve491, that is an excellent point! However, let's expand on it just a little. let's say there is a small vacuum leak in the air damper system. Or the vacuum check value isn't working.

Normally the vacuum check valve along with the vacuum reservoir would keep the damper motors in the selected positions. But when the engine vacuum falls, the vacuum falls too quickly and the dampers change positions.

Get off of WOT and the engine vacuum returns. Dampers return to the selected position (instead of default postion).

Find the vacuum leak, problem solved.

1987stangman · Jun 27, 2011

Not to Hijack this thread but this is the same problem I have been dealing with for 2 years almost. Mine started off in much the same way but now is worse. I have searched for vac leaks in the system but cant find any. It works most of the time but if you get on the pedal hard the blower shuts off -no vent air at all - on A/C or heat and it takes the same to get it back on. Sometimes I can even get in the car to go to work and the blower wont come on for a bit. Come to think of it I did do I radio install about the time it started so I will look for the ground.

bigdog225 · Jun 27, 2011

wmburns said:
+1 on above.

The PCM does not have the circuits needed to turn off the passenger compartment blower.

The PCM does have control of the AC clutch. During WOT, the PCM will turn off the compressor.

For the blower to quit working, there is a loose connection someone. Either in the mode control switch, blower motor itself, or grounding.

The blower is grounded via ground G204. G204 is located behind the center console and it's shared with multiple devices including the radio. G204 is frequently messed up during a radio install.

Not trying to hijack thread but you seem to know quite a bit about the electrical side of stuff. Can you chime in on my thread. Noticed your in Houston. Im in Pearland. Any adivce is appreciated. http://www.stangnet.com/mustang-forums/840883-no-power-ac-clutch-tough-1-a.html

txredgt · Jun 27, 2011

I had another thought on what this could be and I was going to bounce it off guys who know more than me, but could this also be maybe that if the compressor is low on freon shouldn't it cut off so that it doesn't burn the compressor motor? Like a fail-safe not to burn it up?

BULLITT5228 · Jun 27, 2011

The compressor will shut off if real ow on freon, but the blower motor will still work. It was just blow warm air though.

BULLITT5228 · Jun 27, 2011

Posted on my mobile, hopefully yall got what I was thing to say.

BULLITT5228 · Jun 27, 2011

I give up.

txredgt · Jun 27, 2011

No worries I can interpret cell phone jibberish

RoderickGuilbeau · Jun 18, 2012

Steve491 said:
I had a similar problem with my F150. When I went up a hill (low vacuum) it seemd that the blower quit working because you couldn't feel cold air anymore. Turns out it was a vacuum problem with the HVAC dampers and by default, meaning no vacuum, all the air would come out the defroster ducts. When I let off the gas cold air would come out the dash again. It was a quick fix. A small plastic line to the recirculating damper under the hood had deteriorated and fell apart. I spliced a piece of rubber line in and it's been working fine ever since.

Would u happen to know if that applies to a 93 mustang GT ? I'm having the same problem. In park, no matter what the idle,my AC blows cold,but during driving it will stop coming through the vents. Any help would be appreciated in this La. heat !

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