Hi everyone I'm new to the forum but I have owned my Blazer since "97".I recently installed a new engine and trans in it as well as charged my a/c.When I accelarate the air stops blowing from the vents and starts blowing from the floor any ideas on that would be a great help.Also I just installed electric fans and now when I'm sitting at a red light it starts to overheat.I replaced the t-stat and I'm going to do a flush today [fluid looks like mud].The fans flow 2500 cfm and are rated for 250hp with air conditioning I'm to the end of my rope on this one any ideas?

 

As far as the air distribution during acceleration, it sounds like you have a vacuum problem. The HVAC actuators for mode selection are vacuum powered. If the vacuum supply decreases, the system will default into the floor mode. I would look for a vacuum leak somewhere in the system. There are others that have more experience with the vacuum system on these trucks and I'll let them elaborate further.

As far as the coolant temp is concerned, does your fan have high and low speeds? A factory electric fan on most modern vehicles is on high fan at all times that the A/C compressor is active. It sounds like maybe the A/C condensor is giving off too much heat, causing the coolant to overheat. Make sure that the fans are working at their highest speed possible whenever the A/C is on.

 

The fans have only one speed they are pusher fans I wired them as pullers I'm going to try to install them as pushers ands see if that makes any difference.They are flexlite slim fans 2 1/4" thick not really sure they will fit between the rad and cond.As for the vacuum problem I have tried moving the lines around to no avail does anyone have a pic of the vacuum lins for a 97 4wd Blazer?Theres one comming from the trans that I'm not sure where it goes.

 

Dan,
On the 96 Blazer, one line is vacuum source, one is to the actuator under the battery, and the other
is a vent line that runs back up to the rear area of the engine. I am troubleshooting the same problem
now on my 96. I am not sure what is wrong yet. I am waiting on a new transfer case vacuum switch
to replace it and check for transmission fluid in the lines.

[IMG]local://upfiles/3078/9FD24A0F766344828DDDDFD2AF32C455.jpg[/IMG]

 

yup I have the SAME problem on my 95 my blazer came outta Florida and that weather plays HELL on vacuum lines so I went through and replaced all of them under the hood. If you look at that vacuum schematic you'll see there's a check valve right at the main vacuum feed coming off the manifold. Mine's plugged up and I have to go get a new one so I didn't put it back (YET) I'm thinking this is my problem because that valve works in conjunction with the vacuum ball (resivour) that hangs on the underside of the hood. When you are at an idle or low speed the butterfly on the throttle body is partially closed thus the enging is trying to pull air and creating a NICE vacuum. Now you accelerate and that butterfly opens up thus feeding the engine what it wants and bringing the vacuum in the intake down so what would happen here if everything were hooked up and working properly is the check valve would close off and you'd have reserve vacuum in that resivour (ball) that would see you through until you let off the pedal and that butterly closes and you build up a good vacuum again. SOOOOOO I'd first off check those 2 components and that they are in proper working order.. then go from there if it's not resolved and start runnin' down leaks...:P



Just my 2 cents worth
Aqua

 

Well said Aqua teen hungerforce.

napalm dan, you can install a vacuum gauge to see where your at. Plus its fun to watch the needle go bouncy bouncy. Welcome to the forum.

 

ME TOO!!
my 85 stops blowing air out the dash vents going up hill. I fixed a heater switch it was leeking, but still looking for more vac. leeks.

 

I replaced all the vacuum lines and it to care of the air going away.I also back flushed radiator it still gets just above 210* when sitting still @ a redlight.I'm kind of afraid to tow my boat in 100* weather the jury's still out on the electric fans.

 

Rad cap?

 

Dan,
Just a FYI it's not the best idea to hook up an electric motor in reverse..ESPEDCIALLY a fan.. yes you can do it.. and it'll work, BUT... those motors are wound to give you the torque at a specific direction. On the fan note... if you look at that fan... you'll prolly see that the blades are not symetrical. that's cause you have a leading and trailing edge and they're also designed to give you maximum efficiency in a specific direction.... so you're prolly steppin' on your own pecker there TWICE even....