Drag when running heat or air
- Thread starter Ghost
- Start date
That's the normal behavior when the AC compressor comes on and steals a few HP. Pull the AC relay from the front fuse block if you want to prove it. How many vehicles have you owned before now?
- Jun 1, 2012
- 932
the roadie said:
5
First car was a real jalopy rusted 57 ford fairlane it was given to me. No AC
Second was a 1989 vw jetta diesel another pos hand me down. No AC
Third was a 1999 vw jetta tranny went bad. AC never worked.
Fourth was a 2007 Chrysler sebring. Never had an issue until it was totalled.
Current vehicle is a 03 trailblazer
RayVoy
Member
- Nov 20, 2011
- 939
Ok, that's probably not the compressor.
The blower motor will run faster (more voltage will be across the motor, instead of the voltage divider resistors); but the additional load on the alternator should not be high enough to load the engine.........hmmm, but maybe it is.
As I'm typing, I'm thinking that between the alt and the battery, the pair should be able to run the blower without any problem, but maybe one of the 3 is defective.
Perhaps the blower motor is not turning freely and causing a larger load, not high enough (yet) to blow the fuse, but enough to overload the alt.
Perhaps the alt is having problems when a demand is applied and overloading the engine.
Perhaps the battery is not provide the storage required and overloading the alt.
The blower motor will run faster (more voltage will be across the motor, instead of the voltage divider resistors); but the additional load on the alternator should not be high enough to load the engine.........hmmm, but maybe it is.
As I'm typing, I'm thinking that between the alt and the battery, the pair should be able to run the blower without any problem, but maybe one of the 3 is defective.
Perhaps the blower motor is not turning freely and causing a larger load, not high enough (yet) to blow the fuse, but enough to overload the alt.
Perhaps the alt is having problems when a demand is applied and overloading the engine.
Perhaps the battery is not provide the storage required and overloading the alt.
The blower fuse is 30A. At 14 V, that's only 420 Watts. Under 2/3 of a horsepower additional load on the alternator.
If losing 2/3 HP is a noticeable drag I'd be shocked.
I bet it's some psychological effect of more wind blowing in your face.
If losing 2/3 HP is a noticeable drag I'd be shocked.
I bet it's some psychological effect of more wind blowing in your face.
- Jun 1, 2012
- 932
the roadie said:The blower fuse is 30A. At 14 V, that's only 420 Watts. Under 2/3 of a horsepower additional load on the alternator.
If losing 2/3 HP is a noticeable drag I'd be shocked.
I bet it's some psychological effect of more wind blowing in your face.
The timing from a freeway on ramp to the freeway without the air running and.blower is great if i take the same.ramp and run the blower my torque is crap feels like im flooring moped:thumbdown:
The more demand you put on your A/C, the more load on the engine. You have 3 hp drains when you crank the A/C to max - the blower (roadie already discussed), the A/C compressor (good for a few hp loss) and the engine fan, cranked to max because you are demanding the most from your A/C (good for a whole bunch more hp).
The engine fan is probably having the biggest effect.
Is there a way to force the A/C compressor off? If so try it then repeat with the fan on high vent instead of high with A/C. I have to ask the last question b/c I'm not a TB driver.
The engine fan is probably having the biggest effect.
Is there a way to force the A/C compressor off? If so try it then repeat with the fan on high vent instead of high with A/C. I have to ask the last question b/c I'm not a TB driver.
- Jun 1, 2012
- 932
deekster_caddy said:
If its any help i never never use my a/c. I do use the blower button to get more air but that's it. I guess i need an E fan. I could tottaly see the oem fan in the front of the engine causing massive hp loss & drag. Ill try what u said little bit later today its still rainy outside
RayVoy
Member
- Nov 20, 2011
- 939
Guys, the OP does not always have the AC compressor running.
He claims it happens with AC, or with heat and only when the blower is on 5. It appears the blower is the problem.
But just to terminate this AC theory..... these engine have all kinds of torque and hp, the AC compressor should not be noticed at 70 mph.
Ghost said:
He claims it happens with AC, or with heat and only when the blower is on 5. It appears the blower is the problem.
But just to terminate this AC theory..... these engine have all kinds of torque and hp, the AC compressor should not be noticed at 70 mph.
Ghost said:
This is certainly a strange occurrence, The only diagnostic stretch I can make for the issue is a serpentine belt that is too long and when the Alternator, Water Pump, A/C Compressor and Power Steering Pump all team up and cause it to slip. This MAY be felt thru the Steering wheel as "Heavy"
Usually the Power Steering is not needed at Highway speeds so I'm not sure why it would be difficult to keep it straight.
The OP has an EXT so if the longer belt is installed, it would be possible to slip.
And the problem doesn't happen at blower speed 3 or 4? There's less than 10A difference between these speeds and 5.
Can you see the voltmeter droop on the dash when you do this?
What happens if all the windows are up, and you press TWO of the window switches to try to raise the windows? This adds 20-30 Amps to the load on the engine, which should definitely droop the voltmeter.
EDIT: How about adding the electrical load of the rear window defogger? What happens then?
Can you see the voltmeter droop on the dash when you do this?
What happens if all the windows are up, and you press TWO of the window switches to try to raise the windows? This adds 20-30 Amps to the load on the engine, which should definitely droop the voltmeter.
EDIT: How about adding the electrical load of the rear window defogger? What happens then?
- Jun 1, 2012
- 932
the roadie said:
No rear window defogger??? Sucks. When pressing two switches everything dims out like the truck is going to stall. If im sitting at a light at night and press two windows switches up even the windows are up rpms drop to almost 500±.
On free way at 70mph and.doing thw same with the switches feels like truck is going to stall lol.
Ghost said:
A couple things to try:
remove the serpentine belt and free-spin the alternator pulley. Does the alternator make grinding noises while spinning?
load-test the alternator. You should not be seeing that much engine drag from the alternator under load, even a high output alternator.
Then:
Check all your grounds and even clean them.
Make sure the battery cables are snug.
Check the main positive cables at their endpoints.
And does the power steering change behavior?Ghost said:
As suggested, load test the alternator and the battery, and I think you said you had a clean throttle body, then suspect a dirty CPAS for not being able to let the engine hold a solid idle.
- Jun 1, 2012
- 932
the roadie said:
No it does not. Uh where is the serpatine belt ? Btw my battery is a ghetto walmart brand and last summer accidental stripped the positive post so i had to cross thread the bolt in. I operate VHF in the truck even at 50w without any dimming problems. I bet if i go buy a megatron interstate battery all these problems will go away(atleast i hope).
Voymom
Member
- Feb 3, 2012
- 2,523
I watched your video, and I have to say I am almost 100% sure it is your battery, my truck would do the same thing. My battery was having a VERY slight issue holding a charge, but other than that it tested out okay. The Battery was from Walmart and was less than 2 years old. I bet all your symptoms go away with a new battery.
Just my 2 cents
Just my 2 cents
Seems like a bad connection or weak output voltage regulator. Remove the alternator and get it tested. A new battery would only serve as a bandage due to its higher reserve capacity when new. And I think AM noise is related to a faulty bridge rectifier.
Ghost said:
That's pretty vague. I would suggest a good alignment and suspension inspection + brake inspection if your vehicle is wandering or pulling on the highway.
Power steering and belt do not correlate well with your description. With the rate that the tires spin on the highway you could have zero power assistance and should still be able to steer fine.
If its possible I would test by removing the belt and quickly getting on the highway up to 65 mph and see if you still have a problem. Just watch the temp guage and put it in neutral and turn off ignition and coast to a stop if needed. Keep your belt and wrench on hand to reinstall it in the field. Possibly a very screwy power steering pump but highly unlikely given your description.
- Jun 1, 2012
- 932
Maybe its just me...no its not the steering pump, power steering works great. I doubt the suspension is going bad. I recently went to a small mom & pop shop and everything checked out ok except my windshield spray was empty 
oh and the exhaust was a little loose
oh and the exhaust was a little looseGet another opinion. Not knocking your mom and pop shop but they should be able to replicate the issue with you and them in the vehicle. If they were at all knowledgeable then they would recommend a fix. If they did but didnt find anything go somewhere more knowledgeable. I would go to a specialist in steering and suspension who can guarantee a fix, not a mom and pop place.