Does your Mustang do this?

[black94gt]

I have a question about my 1994 Mustang GT 5.0L. Its all stock with 99,000 miles and 5-speed transmission. The issue is my car loses power when I turn the heater on to defrost or to Mix. It feels like I have my AC on because my car starts to surge and noticeably lose power while cruising. As i'm just driving normally down the freeway holding the throttle steady keeping it at the speed limit 60mph I turn the defroster on to keep my windows from fogging up with the heat dial set all the way to the right in the red. I then immediately feel my car lose power slightly and it faintly surges. This happens while I have it on "defrost" -or- if I have it on "Mix". The only setting where I dont feel any power loss is when its on "Vent" or "Floor".

Is this normal? Or is this a problem?

Pic of my control panel

Pic of my stock engine bay

 

[Green Hornet]

Its normal because it puts a load on the engine. ... unless it wants to die. Then it may need a tune up.

 

[96GT02]

its normal as far as i know, happened of my 04 mach and now my 96 also.

 

[joekd]

Defrost also runs the AC compressor

 

[ttocs]

strange I have never noticed it before.

 

[black94gt]

I did a full tune up with plugs, wires, cap, rotor, coil, air filter, fuel filter about 6 months ago.

Driving around town there is not much noticeable power loss but when im on the freeway with the defroster on it makes the car surge (only a little). I dont like it so I always turn my defrost on just long enough to unfrosted my windows and then switch it over to Floor. Since its normal I wont have to worry about it anymore. THANKS

Anyone know how to make your fan motor (heater blower) quiet? When I have it set on the lowest speed the fan makes a lot of noise at low RPM. My car is 18 years old and starting to make many noises lol

Thanks again for the time everyone!

 

[mygreengt]

fyi, grey font is a little harder to read.

 

[black94gt]

fyi, grey font is a little harder to read.

My Font is "black" I dont see any grey on the thread...?

 

[1997GT4.6]

Can't answer that; never get to use the defroster nor heater here

 

[CC'S95GT]

best thing to do is replace the blower motor itself.

 

[evilcw311]

ac compressor kicks on with defrost and mix!! if you dont like it then u can just pull the plug on your compressor for now, but you will need to remember to hook it back up before spring.

 

[ttocs]

it doesn't happen when you have it set to floor correct? I would suspect something wrong with the blend door leaking and causing a vac leak/problem.

 

[fastbanshee1999]

Completely normal operation. It will mix cold air from the refridgerant system and warm air from the cooling system to defrost the windows when set on defrost. you have nothing to worry about.

 

[black94gt]

Thanks so much! I hear it's supposed to be a really bad winter over here again this year so I need my heater to work properly! I'm probably going to load the trunk up with sand bags. I have alot of experience with snow but if my GT is anything like my 79 olds cutlass in the snow Im in trouble.

 

[Matt94GT]

Defrost also runs the AC compressor

This is mostly why....like mentioned.

 

[Patron022]

My sixxer does this too. Like everyone else said. A/C Compressor.

 

[Twista]

normal. Slight surge like the car is running out of gas.. for a split milli second then it comes back to life.

 

[Steven]

You may have a minor leak in the AC vacuum lines that shows up when you mess with the HVAC system.

 

[12vcity]

My friends have encountered this problem,I think it is normal,The car's power is limited,So ...
Read more http://www.youtube.com/watch?v=7mPeGQHbhc4&feature=mfu_in_order&list=UL
hope it help you.

 

[94GTstanger]

Ok...idk what kind of crack everyone is smoking but your car SHOULD NOT surge when you turn the heater on. Your "mix" or "defrost" controls have nothing to do with the temp of the air coming out of the vents...its controlled by the temp button in the middle. It operates a door and when set all the way to hot it closes off the cold side completely and opens very little the more youmove it to the cold side and when all the way cold is supposed to shut off the hot side completely. You should not be able to feel your car lose power when you turn anything on in your car bc the electrical systems works at milliseconds, much to fast for a person to notice. If its surging or losing power I would look/listen for vacuum leaks. I wouldn't think its an electrical prob since it doesn't do it on any other settings but it could be a short in those two positions somewhere. But it is not a normal operation!!