mo650chopper

After I decided to turn it off going up a long hill to see if my instant MPG would change, Turned it back on now it doesn't work. Swapped relay with rear gate latch no change. Can someone tell me how to correctly test the Air Conditioner zener diode? Last hope for cheap repair, Thanks!

843de

Here ya go, had to drag out an old textbook for this, looked through the service manuals and didn't find an input voltage specified for the diode....heck try finding the diode, but I'd guess the input current should be less than 6 volts.

"The testing of zener diodes requires a variable dc power supply. A typical test circuit can be constructed, as shown in figure 4-19. In this circuit, the variable power supply is used to adjust the input voltage to a suitable value for the zener diode being tested. Resistor R1 limits the current through the diode. With the zener diode connected as shown in figure 4-19, no current will flow until the voltage across the diode is equal to the zener voltage. If the diode is connected in the opposite direction, current will flow at a low voltage, usually less than 1 volt. Current flow at a low voltage in both directions indicates that the zener diode is defective."

mo650chopper

I was hopeing it was as easy as I remebered from tech school. Like continuity one way and not the other.

bk94si

check the fuses

843de

Nope zener diodes are pesky critters that have to be tested using a variable power supply, straight diodes won't flow current if they are reverse biased(actually they flow a very small amount, but its insignificant in most instances), but zener's are a different kettle of fish.

larkstar

843de has it right.. but to add a little...When you forward bias a zener diode (+ voltage on the anode) you should get about 0.7 v. The anode is the end with no stripe. The reverse bias voltage will depend on the particular zener voltage of that diode; they are sort of like resistors, they come in a wide range of values. You can usually get the device number off of the diode and find the zener voltage in a semiconductor data book.

working on it

I also turn off the A/C when I need a little "extra" hp; am I risking the loss of my A/C also. I used to have a S-10 2.8l that I rigged a toggle to cut off the compressor for the same reason...but in 18 years of use, it never failed. Should I desist in this practice? I would've also rigged a toggle on the HHR, but was afraid to set off engine codes or something else.

mo650chopper

Checked the "AC" fuse, think it was a 10 amp and it was good.

mo650chopper

I checked and my Compressor clutch isn't locking and running the compressor. It was over a 100 today, only suppose to be mid 90's tomorrow. Probably wi;; check for power at the clutch to determine if that's the problem. Looks like it will be fun to get to. I think what happened to me was just bad luck or timing. It should be able to cycle on / off without an issue as long as there's a bit of time for pressures to equalize.

Lucky

I wounder if something just got freaked out by turning the a/c off and on Im not sure about the hhr but on some gm cars if there is a fault code in the pcm for the a/c system the a/c will not work untill the code is cleared. might want to make a trip to the part store and have the codes read or unhook the battery for a few min.