So I installed a BMW 2 speed fan in my jeep. For sake of understanding the issue assume it is a Tauras fan.

Here is my set up (temporary until I get a continuous load solenoid)

95 XJ 4.0
Stock Amp alt
A/C that blows very cold (important for the issue I am having)

2 speed fan

High Speed:
Ford starter solenoid.
80 amp fuse and 6ga from the solenoid to + Battery
Went with 10ga from solenoid to fan
18ga from selenoid to On-Off-On switch in cab
10ga ground wire attache to plate of solenoid


Low Speed:
40 Amp ford relay
30= 10ga to 12volt threw 40amp fuse
87= 10ga to fan
86= 10ga to ground
85= 18ga to switch in cab
Switch in cab
On- Low speed (40Amp relay)
Off-Power to ignition 12volt
On- High Speed (ford solenoid)


Issue I am having may not even be related to the fan install. I never really ran the A/C before because it would get a little warm.

What is happening now. All issues while sitting at idle
Start it up. let warm up until t-stat opens at 165F turn low speed on. Temp holds for about 5 mins. Turn off fan to let it warm up to about 215F. Turn on high speed. Temp holds for a bit and drops a little, but holds around 210. Turn A/C and temp drops instantly (secondary fan un-plugged completely for now). Air blows cold.
Look at the voltage and it is almost gone. Turn A/C off voltage and temp go up.
Same on either Low or High Speed for voltage droping when A/C is on.

Same results weather blower is on or not.

A/C on with no fan voltage drops to below 9 in the red. I havent pulled any meter readings yet.

I know the Stock Alt is not that powerfull around 117AMP, however it should be able to handle the A/c and 1 fan on low speed.
Any thing pop out at you that could cause these issues?

 

The 2 speed fan is wired completely independently, correct? That's how I read it. I see absolutely no reason why the additional fan would cause a voltage drop.

You're saying the voltage and temp gauges both go up instantly when you turn the AC off?

It doesn't do this at all with the new fan turned off?

Perhaps some interference is screwing with the gauges. First step for me would be testing voltage at the battery and alternator in different situations.

 

It sounds like the load is too large for your battery/alternator. if you run the ac with out the high speed fan on does it drop as much? if you rev it do the gauges respond correctly? I had something similar with a stereo system. I ended up catching the alt on fire and needing to get a HD one.

 

It is killing the bat. It wont start without a jump after voltage drops.

New bat less than 6 mo. Alt same way

Yes when I turn A/C off voltage goes back up and temp starts to rise aswell. Same in reverse if A/C on temp drops and voltage aswell. (I have always seen it go the opposite way lol.)

I cant drive down road to do moving test because I have front end tore apart doing hubs and locker install.

 

is it an instant killing of the battery or if you keep running it? if the latter that makes sense. you could always pull the bat and alt and have them bench tested. if you are running a liquid battery, they are more succeptable to this. a yellow top optima or the duralast equivilent should help though. This deffinately sounds like the same overload issue I had. time to upgrade the charging system

 

I am leaning towards a bad ground short somewhere. It has got to have something to do with the A/C. Its weird that engine temp drops with a/c on. It should go up a little with a/c on. Wonder if compressor pulley could have something do do with it. IDK

 

the temp sensor works off of voltage and a resistance that builds from the temp of the coolant. If you have such a dramatic voltage drop it would directly impact your readings.

 

if I have found out anything about electrical stuff on my jeep, it's that the grounds have to be good and that sounds like a bad ground. But I don't know much about this.

 

I agree. with what you are saying. But the readings wouldn't matter as there is something pulling the actual voltage. It drains the battery too. So something is pulling a crazy amount of power related to the A/C. I am going to go and do some more testing in just a few mins.

Yeh I'm leaning towards ground. In my mind it has to be related to the A/C. I have all new grounds on everything. I just done an engine swap a few months ago.

 

Seems like it would be A/C related since your voltage drops significantly if you turn the A/C on. There is probably a short somewhere. Is it only when the defrost fan kicks on? If you removed the defrost fan and kick your a/c on and didn't isolate the wires, this could be where it is shorted.

 

Humm. I never thought about there. The factory wires that I have disconnected is where I will look next. I have the A/C fan wired to ignition to but unhooked for right now testing purposes. I will check that before I give up. My worst case scenario is to add a second alt where the compressor is now. Then I will have power for days.

 

Does the alternator put out around 14volts? Will the battery pass a load test. Have someone start the car, while you volt meter the battery. Battery voltage should not drop below 10volts.

You have to make certain of these two first. I don't care if both are brand new. You have to comfirm this.

 

Adding a second alt doesn't fix the problem, it will just mask it. You need to find what is sucking down the power and fix it.

 

Would be quite the coincidence if the alternator or battery **** the bed right after the new fan install. But check anyway just to be certain.

 

My last test I noticed the A/C compressor was scalding hot at the pulley. Way hotter than it should be. I am going to figure out where the problem is but feel like it will turn out to be A/C and I will then do a second alt. If it turns out to be simple great. A/C on drains voltage with the electrical fan on or off. Seems to act normal with a/c off and electric fan on. But temp rises a little.
I think Compressor related. Does it on defrost aswell when compressor kicks on. A/C blows cold but there is an issue there. I agree I could be an issue with the factory wires for the A/C fan. I will check that tomorrow.