• Welcome Visitor! Please take a few seconds and Register for our forum. Even if you don't want to post, you can still 'Like' and react to posts.

HVAC switch blows fuse but only in some settings


ericbphoto

Overlander in development
TRS Event Staff
TRS Forum Moderator
Supporting Member
U.S. Military - Veteran
TRS 20th Anniversary
VAGABOND
TRS Event Participant
GMRS Radio License
Joined
Feb 7, 2016
Messages
15,214
Reaction score
16,350
Points
113
Age
59
Location
Wellford, SC
Vehicle Year
1993
Make / Model
Ford Ranger
Engine Type
3.0 V6
Engine Size
3.0L
Transmission
Manual
2WD / 4WD
4WD
Total Lift
6"
Tire Size
35"
My credo
In theory, theory and practice are the same. In practice, they are different.
Good job and congratulations.

It sounds like the coil in the relay has failed. After time, the insulation in coils, motor windings and other electrical devices deteriorates and eventually allows the electricity to leak and jump across wires in the coil. This bypasses the rest of the coil of wire and the resistance it contains, thereby creating a low resistance, or "short" circuit which allows excessive current to flow.

The deterioration of Insulation is accelerated by heat, dirt and chemical exposure. So, the engine bay of a vehicle is a bad place for electrical stuff.

Sent from my SM-G920V using Tapatalk
 


marknreimer

New Member
Joined
Jun 22, 2017
Messages
16
Reaction score
0
Points
1
Age
38
Well unfortunetly it looks like my fuse issue has come back. I had no issues for a couple days but yesterday it popped again as soon as I went to set the vent to the first position to the right of OFF, which is dash vent and floor boards.

Last time when I pulled the blower relay, I wouldn't pop a fuse. So I tried that again, but this time the fuse DID pop.

I had also had success by unplugging the AC compressor clutch, so I did that, fuse popped again.

So I unplugged the ac clutch, took out the relay, and unplugged the pigtail at the back of the compressor too. Nothing blew at this point, so I started putting the stuff back together. Then my blower worked again!???

So I left the engine running and wiggled all the connections, shook the wiring harness, tapped on the fuse box, relay, dash controls, everything I could think of to make a short rear its head. Nothing happened, it just kept working.

I came back an hour later and went on a drive. A few minutes in I switch on the floor board vents and POP.

What is going on?? I've tried to isolate the blower circuit, the AC compressor and clutch circut, the relay, sometimes a test comes back as bad, then the next time as good, and so on.

Since I've blown a fuse now with the ac compressor disconnected, and I've also blown a fuse with the blower relay disconnected, does that narrow it down to the dash switch, or some bad wiring between the switch and the vent doors?



Sent from my iPhone using Tapatalk
 

telsar

Member
Joined
Jun 23, 2017
Messages
57
Reaction score
4
Points
8
Location
Houston TX
Vehicle Year
93
Make / Model
ford
Transmission
Manual
Defrost setting turns on the AC compressor.
 

marknreimer

New Member
Joined
Jun 22, 2017
Messages
16
Reaction score
0
Points
1
Age
38
Defrost setting turns on the AC compressor.


Yeah, but I'm blowing it in the floorboard position, which comes before defrost on the dial.

I disconnected my AC pressure switch by the blower since it's tied to the same fuse. Haven't blown it after two short rides. Gonna keep driving for the day and see if it keeps up. Might have a fault in that bit of wiring


Sent from my iPhone using Tapatalk
 

marknreimer

New Member
Joined
Jun 22, 2017
Messages
16
Reaction score
0
Points
1
Age
38
Well it's been a few days now and about a dozen trips without blowing the fuse. So it's safe to say that it's a short in the harness related to the pressure switch on the back of the AC compressor. Time to find the multimeter


Sent from my iPhone using Tapatalk
 

Sponsored Ad


Sponsored Ad

Staff online

Members online

Today's birthdays

Member & Vendor Upgrades

For a small yearly donation, you can support this forum and receive a 'Supporting Member' banner, or become a 'Supporting Vendor' and promote your products here. Click the banner to find out how.

Truck of The Month


Kirby N.
March Truck of The Month

Recently Featured

Want to see your truck here? Share your photos and details in the forum.

Follow TRS On Instagram

TRS Events

25th Anniversary Sponsors

Check Out The TRS Store


Sponsored Ad


Sponsored Ad

Sponsored Ad


Amazon Deals

Top