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Tim Mohr
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isuzu trooper: no power to c19 fuse

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no power to c19 fuse
Hi, my name is XXXXX XXXXX motor do you have in this?
Customer: replied 4 years ago.


ok, the C-19 fuse gets its power from the heater/ac relay, have you tried swapping this relay with another?
Customer: replied 4 years ago.

No, I need to know the where the relay is located?

the relay is in the fuse box in the driverside kick panel under the dash, I will post a picture showing its location, you need to swap the heater/ac relay with one of the other relays there and see if you get power to the C-19 with the key on, can you do this?






Customer: replied 4 years ago.

I switched the heater relay with the power window relay and with the key on there is still no power to c19 fuse

Customer: replied 4 years ago.

I tested all four spots where the heater relay plugs into, one spot had 12.7V and one had .72V and the two others and 0V. I tested the other two relays and both had two spots that had 12.7V, and two that had 0V

Customer: replied 4 years ago.

I know the blower system is working. I just tested it by jumping another wire in the fuse box to c19 fuse. What do you think?

ok, then this is going to be the problem, you need 12 volts at 2 of the terminals, one of these terminals gets its power from the starter relay, and one of them gets its power from the 80 amp main fuse, can you first check the main fuse?

Customer: replied 4 years ago.

The 80 amp main fuse is good.

ok, then we need to swap out the starter relay in the same bix as the main fuse, swap it with another relay of the same type, and see if you now have power to the c-19 fuse, if not, check all the terminals of the starter relay and tell me which ones have power,Tim
Customer: replied 4 years ago.

There are six prongs, four on the outside and two in the center. The one in the very center has 12v. The one in the outside center has .72v. All of the other ones have 0v. This was checked with the key on.

ok, stamped on the bottom of the relay, there should be numbers for the terminals, can you tell me the number on the terminal that has only .72 volts?
Customer: replied 4 years ago.

The only numbers on the relay are on the side on a sticker and do not correlate with the prongs. Do I have to take apart the fuse box to look underneath?

you may have to, but first, lets check the white wire with a green stripe at the alternator, this is the wire that supllies voltage through the starter relay for the heater relay, see if it is the one with only .72 volts,Tim


















Customer: replied 4 years ago.

When looking at the alternator, I found that the belt was in pieces. I will change out the belts, but do you think this is the problem or do I need to keep looking?

this probably is not the problem, but it could be a bad alternator, but first check the wire and tell me how many volts you get on the white/green wire?
Customer: replied 4 years ago.

Took me a moment, I had to remove the wheel. The white/green wire has .72v.

in the dash fuse box, do you have 12 volts on the c-10 fuse with the key on?
Customer: replied 4 years ago.

With the key on, the c-10 fuse has 12v.

on both sides? if yes, then turn the key on and see if the battery light on the dash comes on
Customer: replied 4 years ago.

I am not sure I understand. With the fuse pulled, I can test both sides of the fuse housing and one side has 12v and the other side 0v. With the fuse in and the key on, the battery light does come on. Does this answer your question?

ok, this fuse sends power through the light, then off to the white and green wire, can you go back to the heater relay, and check all the terminals with the key on, an dsee if you now have power on at least 2 terminals? I have to close up the shop, but will be home in a about an hour, can we continue this then?
Customer: replied 4 years ago.

With the key on the heater relay has 2 terminals with 0v and one with 12v and the other with .72v. Yes we can continue when you get home.

Customer: replied 4 years ago.

I am watching the email. Did you get the last message about the heater relay terminals?

i am sorry, i had problems with my internet last night at home, if you still have only .72 volts at the heater relay on that terminal, we need to disconnect the whote green wire from the alternator, and then check for a full 12 volts at that terminal, it sounds like the alternator has an internal short and it dropping the coltage on that wire, can you do this?
Customer: replied 4 years ago.

I had the alternator tested, and it tested out fine. I am going to put the new belt on and see what happens. I will let you know.

did you disconnect the white/ green wire from the alternator and see if you have a full 12 volts to that wire?
Customer: replied 4 years ago.

I tested it and it started out at 0.8v, but as I held the tester to it, it randomly fluctuated all over the place and went as high as 11.7v and stayed there.

Did you check this with the wire disconnected from the alternator or with it hooked up?

Customer: replied 4 years ago.

With the wire disconnected.

and back at the heater relay, does that wire also vary from .8 volts to almost 12 volts?
Customer: replied 4 years ago.

With the alternator hooked up, the heater relay has .72v.

with it unhooked, what is the reading at the heater realy?
Customer: replied 4 years ago.

With the alternator unhooked, 12v.

then the diode in the alternator is dropping the voltage, the alternator could have checked out good on the bench, but they usually only check the alternator output, and it can be good, even with a bad diode, I reccommend replacing the alternator,Tim
Tim Mohr and 2 other Car Specialists are ready to help you
Customer: replied 4 years ago.

I called O'Reilly's, which is where I had the alternator tested. They said they use an OTC tester model 4643, which tests the output, rectifier, diodes, and regulator. The OTC tester has a program for specific parameters for that alternator.

What you are not understanding is you have the correct voltage on that wire with the alternator disconnected, so it can only be a problem with the altermator,Tim

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