Dual fans blowing fuse w/ AC engaged??

[87NAT]

My g-body dual fans setup with the caspers plug n play harness is blowing the 30 amp fuse on one of the relays as soon as the A/C is turned on.(the fuse going straight to 12+ battery connection) I have had the fans for over a year and have never had issues.

It doesnt blow both of them. The fans work as normal without the a/c and are turned on at 160 as per the TT chip. They also come on and work normal when the coolant temp switched is manually grounded. I have not used the a/c in about 5 months and not since the new engine rebuild. The fuse blows immediatly. What could this be? Bad relay? Shorted wire somewhere? I am no electrical guru and this is one that I am not looking forward to tackling. Please give me some basic instructaions as to what wires to check. I have a test light and ohm meter.

 

[VIN7]

Maybe check the plug on the a/c compressor (between the pulley and compressor), look for a resistor if the bare wires on the resistor touch anything it will pop the fuse. If they are exposed just insulate with tape.

Mike

 

[87NAT]

Thnaks Mike...will do.

I was speaking with Allan(SalvageV6) about just disconnecting the pressure switch plug on the A/C since my dual fans run on high all the time and come on at 160 degrees. It could be a quick fix if I cant find the problem. I know down here in Lafayette in the summer the fans will be on 2 minutes after I leave the house and the A/C will get the fan cooling effects even though the switch is not hooked up. What is the opinions on this?

 

[Roger]

I'm afraid I'm unable to help with the problem any more than VIN7.

I definately would not run the ac without the fans. No fan would cause excessive pressures in the ac system. These systems are over 20 years old & PROPER repairs are very costly. Most ac places want to use 134 instead of freon 12. 134 doesn't even work properly on the newer cars & especially not on a system not designed for it.

Again - DO NOT run the ac without the fans. Find & repair the fuse blowing trouble or keep the ac in the OFF position.

 

[87NAT]

I have been reading the service manual. Please follow me on this:

The high pressure switch from the a/c goes to the high and low speed relays as needed per freon pressure. The ECM goes to the low speed and the coolant temp switch on the intake goes to the high speed relay. After testing the coolant switch and knowing the ECM turns on the fans also that tells me right away that BOTH relays work okay. The A/C pressure switch is tied into both wires along with the coolant and ecm wire(high & low). If they are all tied in together and there is a short why would the fuse not blow everytime?

 

[GNVenom]

Which fuse goes out? The "Relays" fuse in the GN fuse panel?

Try disconnecting the clutch connector (flat black two wire connector) and cycle the AC. The compressor won't run, but you should be able to determine whether the clutch is at fault. There is a diode in the clutch connector where, wnen shorted, can take a fuse out immediately. I'd suspect that diode is shorted.

As a quick fix, cut the diode out of the connector. The AC clutch spike will be prevalent, but should run OK.

 

[87NAT]

Which fuse goes out? The "Relays" fuse in the GN fuse panel?

Try disconnecting the clutch connector (flat black two wire connector) and cycle the AC. The compressor won't run, but you should be able to determine whether the clutch is at fault. There is a diode in the clutch connector where, wnen shorted, can take a fuse out immediately. I'd suspect that diode is shorted.

As a quick fix, cut the diode out of the connector. The AC clutch spike will be prevalent, but should run OK.

John, the fuse that is blowing is the 30 amp blue wire fuse on the casper harness going straight to the 12+ battery. Only one of the fuses blow. The connecter to unhook is the one in the front of the compressor with the little u shaped jumper wire on it? Do you want me to unplug this connector or cut that U shaped wire?

LEt me know. And thanks for the quick reply.

Ed

 

[GNVenom]

If you are talking about a "fuselink" that is blowing, that's a different story. The only thing that can open a fuselink is a dead short in the fan itself, or short in the connection. The link protects the wiring in the event of a "crowbar" short, or dead short.

There are three terminals in the connector that interfaces the Caspers harness to the GN fan wiring. A, B and C. A is low speed, B is high speed, and C is ground. If your fuselink opens when the AC is requested, terminal B goes to 12v. which energizes the high speed relay in the Caspers harness. Otherwise, when low speed cooling is requested, terminal A goes to 12v. which closes the low speed relay in the Caspers harness. Both relays are set up to control the fans, either low or high, and each circuit is protected by a fuse link.

With your symptoms, it seems as though the high speed motor windings on one of the fans is shorted. Try disconnecting the individual fan connectors within the fan sub-harness itself, one at a time.

what are you doing to fix the blown fuselink?

 

[87NAT]

My question John is that whether its the a/c requesting the fan or the ECM or the coolant temp switch they all go thru the same factory connector. The coolant switch is high speed and the ecm is low. The fans work with no problems on either of those. One fuselink blows only when the a/c is requesting power...how does the capsers relays know which part is requesting power? It shouldnt make a difference. AM I making sense? I see your point about the fan itself being a culprit but wouldnt it be a problem all the time? ECM + low side a/c compr= low speed relay Coolant temp + high side a/c compr= high side relay

 

[GNVenom]

There should'nt be a difference. If you're saying the fans can be controlled with a HI LO switch, so you can manually turn on low or high, and it works perfectly, then I'm not sure why you're opening a fuselink. The AC request turns on either low or high, depending on line pressure - by way of the line pressure switch on the AC line.

Try running the fans via HI LO switch, first on low, then on high, while touching the fuselink to see if it is heating up. The links should be slightly warm to touch, but not hot. If either one of them are hot, you have a motor problem that just happens to show itself when you turn on the AC. I can't think of any other reason since the fans are essentially controlled by the 3 way connector on your GN wiring harness.

 

[87NAT]

I dont have a manual switch. I was just saying that they are working on both the high and low side automaticaly. The ECM turns them on with no issues and when I ground my coolnat temp switch to test them they turn on with no issues. I will do some testing in the next few days when I get a chance. I agree that there is something wrong past the stock GN wiring.

About 3 months ago I unhooked one 12 volt wire from the relaly to the battery to try to get just one fan to run in the winter time and neither fan would come on. WHy is that. I mean the fans work so well that my car wouldnt heat up. Are the relays tied in together somehow?

 

[salvageV6]

What is the model number of the caspers harness you have?

The only Ramchargers dual fan harness I could find on Caspers Elec. site is a stand alone harness with a Hi/Lo switch.

This obviously isn't what you have so what is the part number on your harness?

What you have and exactly how it's wired is truely necessary to get to the bottom of your problem. The A/C pressure switch wiring is just parallel to the ECM and high speed switch wiring, and should have no additional effect on the fan circuits that are already turning on the factory relays.

If they don't blow fuses with the ECM controlling the fans or by you manually triggering the high speed coolant sensor ground then the A/C switch shouldn't blow any fuses either, on the stock setup or with the added harness.

More information is needed to troubleshoot this.

 

[87NAT]

Allan,

The harness is what came with the g-body parts dual fans. It was a plug n play right into the factory 3 wire harness. The only other connections I had to make were a ground from the caspers harness (I ran to the frame) and the two 12 volt fusible link connections straight to the + battery.


I have been going thru the manual myself and you hit the nail on the head as well as John. The fusible link that is blowing should blow everytime the fans come if there is an issue with the fans themselves. They dont know what source is commanding them to turn on(ECM ,a/c, etc...) I appreciate the time and input you have given to me on this. I will do some testing on this problem in the next few days and let you know what I find.

Thanks again,

Ed

 

[GNRick]

When one of my fans went bad it blew one or both of the 30 amp fuses. Can't remember for sure but I would never buy one of those crap Chrysler reject dual fans again. I have heard good things about the Spal fan and I would buy one of those next time. Someone posted recently that the Chrysler dual fan that came stock on the Intrepid is better than the ones that are sold separately. He suggested that you go to the junk yard and pull one off of a junked Intrepid. Just a thought. I think one of your fans is on its way out if it hasn't already gotten there.

 

[87NAT]

When one of my fans went bad it blew one or both of the 30 amp fuses. Can't remember for sure but I would never buy one of those crap Chrysler reject dual fans again. I have heard good things about the Spal fan and I would buy one of those next time. Someone posted recently that the Chrysler dual fan that came stock on the Intrepid is better than the ones that are sold separately. He suggested that you go to the junk yard and pull one off of a junked Intrepid. Just a thought. I think one of your fans is on its way out if it hasn't already gotten there.

It seems that it could be a fan thats the culprit BUT... It just does not explain how I can drive it for almost an hour (without A/C) and have the fan running great. Then get home and ground the coolant temp switch for 2-3 minutes without blowing the fusible link. THEN if I put the A/C on the fusible link blows instantly?????

I am okay now because its pretty cool out but Louisiana summer is coming and I got to get it fixed before the heat gets here. I'm told old to cruise with the windows down anymore.

 

[87NAT]

Finally got time between work and kids for troubleshooting.

I have determined that when I turn on the a/c the load on the charging system is causing the amp pull on the fans to go up therby blowing the fuse. My fans have ALWAYS dragged my motor down when they cam on...I never really thought much about it because they are strong fans.:redface: Anyway when the a/c is engaged and the fans kick on the voltage goes from 14.2 to 11.1 and the motor lugs down bad. The alternator recovers back up to 14 or so volts but its that initial start that gets that fuse everytime. Could a motor in one of the fans be bad?

I am getting ready to wire up one of the fans on my ashtray switch and keep the other on the low side relay. I figure by separating their start up it will keep the amp draw down. I will also be checking each fan motor resistance when I separate the caspers wiring harness.(Both fans are wired together) Am I doing the right thing or am I puting a band-aid on a bigger problem and just covering it up?

 

[salvageV6]

If you wire one fan to a switch do it through a relay good for 40A minimum and obviously use good wiring and a fused power lead.

I still don't know if you are blowing simple ATC 30A fuses or actual wiring fusible links that part isn't so clear....

If it's a fuse in a fuse holder I'd try a 40A fuse AFTER checking all the wiring for any heat damage or bad connections/crimps to connectors.

IF the alternator recovers after the A/C comes on real quick like in 3-5 seconds that may simply fix the surge problem.

However you could also do some testing with jumper cables or large gauge wiring with clips, from the alternator to battery for the positive feed, and the battery to the motor on a good ground connection.

Again note the voltage when the A/C kicks on after beefing up those connections and note any changes.

What exactly is the type and size of fuse or fusible link that is blowing?

 

[87NAT]

Allan, it is a simple ATC 30amp fuse.

I just drove it with A/C on for 30 minutes no issues. I think its fixed!:smile:
I kept one fan on the low speed relay factory connection and I put the other on my ashtray switch. I am still using both casper relays that came with the kit. Now I can turn on the extra fan when needed.

The fan comes with the a/c as ist supposed to and you cant even tell...no rpm drop...no stumble. When I manually turn the second one on the same thing...no stumble or rpm drop. It looks like that cured the probelm...so far.

Thanks for your help.

Ed

 

[salvageV6]

Sounds like you simply need a delay on the second relay for triggering it.

Here's a circuit below that does that, easy to build, 2 wire install, simply remove the TRIGGER +12 Relay COIL wire, attach the existing wire to the circuits +12 input lead, and the output of the circuit goes to the relay coil +12 terminial that is now bare from the wire you just removed.

A snubber diode should probably be used accross the relay contacts not shown in the diagram below but may already be in your harness from Caspers, that's a visual check thing.

They may have a circuit as well you can buy premade that does this.

Building one is easy and relatively cheap if you can find an NTE transistor dealer, 50K is a potentiometer for adjusting the delay.

 

[87NAT]

I had read about those delays because others were having that rpm drop also. I am going to keep it setup like this for those cold/mild days when I dont need both fans on. It was pretty warm today and one fan with the a/c on kept my temps at 175-180.

I will save the info you sent on the delay if I need it in the future. Thanks again for all the PM's back and forth in the past few weeks helping me troubleshoot.

Ed