Radio cuts out, engine sputters when radiator fan kicks on

[mygalantwasfree]

Hey guys,

So I've fixed the majority of my wiring problems, and I believe I just have this one left. Whenever my radiator fan cuts on, the radio goes dead briefly and I notice an unusual drop in engine rpms, like I had just turned on some power hungry appliance. Once the radiator fan is up to speed, the radio turns back on again and all is well. This happens in cycles, the radio cutout exactly coinciding with the kicking on of the fan.

So I'm guessing that the fan motor is briefly drawing more amps than the 30A circuit (fuse #5 in the engine fuse box) is able to carry. What I find weird about this is that I don't blow any fuses; the radio simply cuts off, and then resumes playing when it comes back on.

Things I've tried:
I switched out the radiator fan relays, but same thing.

Does anyone know how many amps the radiator motor is supposed to draw on startup? I can check mine, but I need a working car's numbers to compare it to.

Thanks for putting up with my endless threads. I hope to have this resolved ASAP. I'm not ready to completely give up on ol' Christine yet. I appreciate all of your help!!!

[lobsterman72]

Not knowing the whole story but... From installing car audio for 10 yrs I would start with a new decent battery. Also check the alternator.
When the cars running you should use a meter on your battery, you should get 14.4v or so. When the fan turns on it will drop but it shouldn't drop below 12v. Most car stereos (unless you have a power hog) will cut out under 11.5v or so, this using your car stereo as a make shift volt meter and provided it is installed properly.
Also a temporary fix may be to increase the idol speed a little. I would still try a decent sized new battery. Don't cheap out get a tiny wallyworld battery.

[mygalantwasfree]

Not knowing the whole story but... From installing car audio for 10 yrs I would start with a new decent battery. Also check the alternator.
When the cars running you should use a meter on your battery, you should get 14.4v or so. When the fan turns on it will drop but it shouldn't drop below 12v. Most car stereos (unless you have a power hog) will cut out under 11.5v or so, this using your car stereo as a make shift volt meter and provided it is installed properly.
Also a temporary fix may be to increase the idol speed a little. I would still try a decent sized new battery. Don't cheap out get a tiny wallyworld battery.

You were absolutely 100% correct about the battery. The previous owner was an idiot and installed a battery that was designed for a truck. This 5 year old truck battery strained the alternator, which wasn't designed to charge such a battery. This is part of the reason why I had to install a new alternator. He also install some sort of "premium racing ground wire", which shorted stuff out (from what he told me). So basically I have electrical problems not because the previous owner was an idiot and wrecked the car, but because he was an idiot and tinkered with an already perfectly-working electrical system. If it ain't broke, don't fix it.

Anywho, the old battery was designed to deliver 880 CCA. It was at 300 CCA when we tested it. The brand new alternator was struggling to charge the battery and was delivering ~13.8V at idle, which is below normal. This is what cued me into either the alternator or battery being at fault. Replaced the battery and now my stereo doesn't cut out!!! Helll yeah I'm guessing that last week's constant 30A shorting out was the final nail in the coffin for that duralast.

All of my electrical problems seem to be solved, at least for the moment anyway (crosses fingers)

[beam514]

was going to say the battery is going out, if it can't handle the initial surge of energy to get the fans started

glad you got it figured out so fast

[mygalantwasfree]

UPDATE:

The new battery made the problem go away for 3 days or so, but now it's back in full force I'm ready to just take a hatchet to the entire wiring harness. If I can't fix this, it's going to kill both my battery and my alternator. I really need to know the current draw on that fan. If the fan checks out and is drawing a normal amount of current, then the stupid harness is at fault and I'll have to do some chopping and splicing modification to put that fan on its own separate circuit.

Anyone know the current draw of their radiator fan?

[w/oarctic7g]

Get a cheap voltmeter and find out the voltage at the battery with car running and no accessories on, then turn on high beams, rear defrost, heater and ac. Probe or scratch battery terminals good so you have an accurate reading, both readings should be over 13.5 volts. I have found the cable ends to be a common issue the original ones even after a good wire brushing are junk so you may want to replace with new ends. It is unlikely that the fans are the problem just the straw that broke the camels back.

[mygalantwasfree]

Get a cheap voltmeter and find out the voltage at the battery with car running and no accessories on, then turn on high beams, rear defrost, heater and ac. Probe or scratch battery terminals good so you have an accurate reading, both readings should be over 13.5 volts. I have found the cable ends to be a common issue the original ones even after a good wire brushing are junk so you may want to replace with new ends. It is unlikely that the fans are the problem just the straw that broke the camels back.

I tested it. I got 14.11V with full current load (full blast blower, defroster, hi beams, etc), and 14.05V with no load. The battery and alternator are brand new, and the battery clamps are clean. I bought the clamps ~3 years ago.

[w/oarctic7g]

You might want to check the underhood fuse box for corrosion and make sure the bolts are tight that hold the terminals to the large fuses I think there is at least 4.

[beam514]

you checked it again recently? I dunno if it will be the same, but my buddy bought a brand new aftermarket alternator and it gave his car sooo many problems. He ended up returning it and then got a used OEM one, which fixed everything.

[mygalantwasfree]

I'll check those bolts here tomorrow. As a temporary fix, I wired up a toggle switch in one of the blank plastic pieces to the left of the cruise control switch on the dashboard. The switch can either open or close the ground circuit going into the fan motor. So my plan is to keep the switch in the "on" position while stationary, and turn it off while moving. That will at least keep the stereo cutouts to a minimum, like when I'm stopped.
There's no reason that fan should have to come on at 45 mph. It cycles on and off no matter how fast I go and it's annoying because every time the fan does cut on, I lose the stereo for a second.

I'm betting on this being either yet another problem with the wiring harness (fan wire leaking current) or the fan motor is burning out and drawing way too many amps. I'm suspecting it's the latter.

[oakrdrs187]

I recommend you check the alternator at this point, since you replaced the battery already. BTW the battery was just old, it didn't kill the old alternator. Alternators are always giving off charge, they can't tell what battery you have they send out DC and the battery stores it, if the cell is dead then it won't. Anyway good call replacing the battery. After you run a test on the alternator, check the cables between battery and alternator, replace if necessary. I can almost assure it's the alternator, because you changed the battery and it was good for three days, after the battery drains because the alternator isn't charging it you're back at square one.... On my buddies 95 Maxima, his alternator would cut in and out, took it to Autozone for testing, passed all ten times we ran it (no joke), replaced it and no more problems.

[whyhon]

I have exact same problem on my Honda Civic FD 2007. Just wanna share how i solved this problem.

The syndrome : Radio cuts out & engine sputters briefly when radiator fan kicks on.

What i has done.
1) Replaced an alternator - problem and syndrome remain the same.
2) All wire connections checked and cleaned - problem and syndrome remain the same.
3) Replaced with a brand new battery - problem solved for 3 days and the syndrome (radio/AC cut off briefly) occur again.
4) Finally, adding a cable from negative terminal of the battery to engine block. Problem solved.

If you faced similar problem, you should try (2) and (4) first before trying the more expensive (1) and (3).