Problem with defrost?

[Mike1990]

I have a 90lx with a 2.3 and have been having an issue with my main defroster since i got the car. The battery and alternator are new as well as other charging system bits, but whenever i turn it on the engine seems to lug pretty bad when the ac is engaged and my battery level drops and raises on and off. Im not to sure what to do to go about fixing this. If anyone has some suggestions or info its greatly appreciated.

 

[wbrockstar]

The biggest problem is the stock alternator.Its only a 75amp unit and once you turn high drawing circuits on,like the defroster,blower moter,ac,headlights, it sucks the juice out big time.A 3G 130amp alternator can resolve the issue and you can find them at Pull- A-Part most of the time.The junkyard hp thread below will list which models have them.There should be some 3G upgrade links online.Someone told me the ac compressor comes on with defrost on,but Ive never verified this.If so,thats the main reason for the draw.The blower motor is high draw circuit too.The other things to check are your grounds.The block to firewall ground is used for the ac clutch,gauges,int/ext lights and the alternator.Grounds should be tight and corrosion free.If this ground is weak,your temp gauge will increase as you turn accessories on like the fan,headlights,etc.Adding an additional 4ga ground cable from the fender apron ground to the block and from the block to the pass side firewall helps too.Make sure the alternator/bolts are tight with no paint between the alternator/bolts/bracket.

 

[Mike1990]

Okay. Ive been considering switching the alternator. Ill look in To checking grounds first just incase and then look into another alternator. thanks!

 

[wbrockstar]

I forgot to post the jy hp link for ya.Click the following link then scroll down to the alternator section.
http://forums.corral.net/forums/5-0...orsepower-summary.html#/topics/1092402?page=1

Just to rule it out,loosen the idler tension pulley and pull the serpentine belt off the ac compressor.Spin the compressor pulley by hand to make sure its not seizing up.Now turn the key on/engine off,turn the ac on & fan on then try spinning the pulley again. It should have some resistance due to the clutch being engaged,but it should be super hard to spin.If it is,the compressor might be on its way out and this could cause an excessive load on the engine and electrical system.
To check your charging system,grab a multimeter.Touch the leads to the battery posts.You should get the following results:
Key off/engine off= 12.5+ v
Key on/engine off= 12.5+ v
Key on/engine on= 13.5-14.7v
Key in start position=` 9.6+ v
When the engine is idling and you turn an accessory on,voltage will temporarily drop,but should climb right back up to normal.
Keep an eye on the ignition switch under the upper trim around your steering column.Its made of plastic/pot metal and tends to separate with age,causing loss of power to the dash warning lamps/
gauges/radio/etc.Stalling,hard starts,no starts,etc are also caused by this switch.The diagram below shows the circuits powered by this switch.

 

[count floyd]

I have a 90lx with a 2.3 and have been having an issue with my main defroster since i got the car. The battery and alternator are new as well as other charging system bits, but whenever i turn it on the engine seems to lug pretty bad when the ac is engaged and my battery level drops and raises on and off. Im not to sure what to do to go about fixing this. If anyone has some suggestions or info its greatly appreciated.

Sounds like the a/c compressor is switching on and off due to line pressure or low line pressure, I think the rpm is dropping due to the compressor, during low rpm your voltage drops, , I would unplug the a/c compressor or the line pressure switch, and see what it does, The ecm should detect low rpm when the ac compressor kicks on and adjust the idle.Maybe for some reason its not picking it up. what are the rpm at idle with the defroster on in gear? (if its an auto transmission) when you turn on the defrost you have the cooling fan the defroster fan the cooling fan and the a/c compressor fuel pump relay on that same line i believe, have you checked the voltage at idle with it on and off?

 

[wbrockstar]

Countfloyd brings up valid points.It also makes me think about the iac valve.The iac valve is bolted to the throttle body.Its used for idle control & the ecm is in charge of it.When the ac compressor is engaged,the iac valve is opened to increase idle speed to compensate for the additional load of the compressor. Make sure its working correctly and not dirty.With the engine idling,if you disconnect the harness from the iac valve,the engine should stall or at least idle down slightly.If not,the valve is dirty or suspect.The valve is opened during many running conditions.Its easy to test.It should have 6-13 ohms when touching multimeter probes to its terminals,with its harness disconnected.Reverse the probes on the terminals and it should read 10,000 ohms or infinite.Now touch one probe to the iac valve body and touch the other probe to each terminal individually.It should read high ohms or infinite.If these tests pass,the electrical portion of the valve is good.

 

[count floyd]

found a diagram
http://1.bp.blogspot.com/-s3KHmps0H...Mustang+1988-1990+2.3L+EEC+Wiring+Diagram.jpg

 

[Mike1990]

Thanks so much for the info and im going to be looking into it soon i replaced the i.a.c so i dont believe its doing much and i havent checked with it on and off but like i said im going to comb through it and check evereything. Thanks so much sor the info its been driving me insane