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Tim Mohr
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2003 Altima - had to remove radiator to replace alternator.

Customer Question

2003 Altima - had to remove radiator to replace alternator. Refilled radiator and bled system. Now when using AC, compressor only engages when cooling fans turn on, and disengages when fans turn off. Tried bleeding system again today but same results. Is it a temperature switch problem?
JA: How many miles are on the car? Have you checked the coolant level?
Customer: 73,000 Yes, goo level good
JA: Are you hoping to fix this yourself? What have you tried so far?
JA: Anything else you think the mechanic should know?
Customer: Tried bleeding system per Jay's recommendation on another thread but cant get AC to stay on without fan running.
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the Nissan Mechanic about your situation and then connect you two.
Submitted: 4 months ago.
Category: Nissan
Expert:  Jay replied 4 months ago.

Hello my name is ***** ***** thank you for your question.

Is the car running hot? If engine temp gets to high, the computer will kick off the compressor since it's a load on the engine.

Let me know

Customer: replied 4 months ago.
No, not running hot according to gauge. About the same as before alternator replacement
Expert:  Jay replied 4 months ago.

You did't touch any AC lines right?

Customer: replied 4 months ago.
no, I didn't
Customer: replied 4 months ago.
are you still there?
Expert:  Jay replied 4 months ago.

sorry, wife was talking to me.

Trying to think what would cause this. If you bleed the coolant system the way I outlined it, you really should not have any issues. Was it doing this before the Alternator? Where did you buy the Alternator?

Customer: replied 4 months ago.
happened after alternator replacement. purchased from local NAPA dealer
Expert:  Jay replied 4 months ago.

Do you have a Volt Meter?

Customer: replied 4 months ago.
but did a load check with tester after replacement and alternator output was in the "good" range
Expert:  Jay replied 4 months ago.

What is the voltage with the vehicle running and head lights on and rear defroster ON?

It is very common for after market Alternators not to work properly. It could be intermittently not charging properly.

Customer: replied 4 months ago.
voltage was +13.5 if I remember correctly, steady output
Expert:  Jay replied 4 months ago.

That is low... It shouldn't be lower than 13.9 volts..

Expert:  Jay replied 4 months ago.

Normally with no loads, it should be 14.3 volts. With loads I would expect to see 13.9 to 14.1 volts.

Customer: replied 4 months ago.
it was closer to 14V now that I think about it.
Expert:  Jay replied 4 months ago.

May want to recheck those voltages.. Once with loads, and once with out. Loads meaning, AC on, Lights and Rear Defroster.

Customer: replied 4 months ago.
I suspect something with cooling system, because like you said when engine is hot it sees AC as a load and kicks it off.
Expert:  Jay replied 4 months ago.

Well you have two systems you need to look at. The charging system and cooling system. If charging system voltage spikes low, the computer will also turn the compressor off

Customer: replied 4 months ago.
ok, can double check voltage. is there anything else I can check on cooling system if output checks out good?
Expert:  Jay replied 4 months ago.

Once you start the car and have it running, check voltages with loads off. Then turn the AC on, Head lights and rear defroster and double check voltage. Once you give me voltages, I will try to think if there is something else we need to check. It's sounding like it's going to be one of the two systems in my mind..

Customer: replied 4 months ago.
Ok, but may be a while. How do I continue the chat, just keep this website open?
Expert:  Jay replied 4 months ago.

If you have to close this, all you need to do is to log back into and go to My Questions to return back to this question.

Customer: replied 4 months ago.
ok, got it. thanks
Expert:  Jay replied 4 months ago.

Your welcome

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