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Intermittent Interior Heat


Jeff Wilson

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The heat in my car works intermittently with no codes being thrown. When you get in the car it will work other times it doesn't. When driving it will all of sudden start working.

I had a sunroof leak last year, the drivers side floor panel would get all wet. The drivers side sunroof drain tube popped off.

Any help or guidance would be appreciated. It's pretty cold here in Canada, current temperature is -26 Celsius (-14.8 F) with ice crystals.

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I assume you mean that the temperature gets cool and you are not saying that the FAN stops working

The first thing I would do it check the level of your coolant

then I would make sure that your thermostat is not sticking open

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Sorry about the confusion. What I meant to say is that the fan stops working, it works intermittently. Sometimes it will work ok for 1-2 weeks at a time than all of a sudden it quits. Today, the fan wouldn't blow when I started it up, after about 15 mins of driving the fan started working again. The hvac controls light up as if its working but the fan does not blow. No air flow

Edited by Jeff Wilson
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OK this is a common failure, you need to replace your HVAC fan. But first check the plug to make sure its making good connection

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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I Will check to make sure connections are clean and tight. Otherwise how hard is it to replace the fan and what is involved? I thought I read on here before the engine has to be pulled, I hope I am wrong or misunderstood.

No the engine doesnt need to be pulled. Does your year have dog bones at the top of the engine?, some have detached the dog bones and tilted the engine forward to gain access.

Others will chime in on the motor change, I have not had to do it

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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My car does not have the dog bones at the top of the engine.

The 1998 - 2004 Seville chassis provides access to all the HVAC blend door actuators and blower motors from inside the cabin.

If your car was my car, I would put a lot more effort into diagnostics before throwing any parts $$ at the problem. Corroded connectors come to mind as the first possibilty.

Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

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to me: "intermittent" = a loose connection. the fan probably comes on when the right bump is hit.

suggestion:

when it is NOT working, gently tap on the wires & connectors (including ground wires) leading to the fan. Hopefully, you find the sweet spot & get the fan going. ALSO, make sure you have the temp set to 90 degrees to ensure the fan stays on constantly.

I know a bump can also start a jammed armiture in the motor, but an electrical check should be the starting point.

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I would like to change the relay which controls the fan motor. Can someone tell me the number of the relay that controls the fan. I checked the connection at the fan motor it looks to be ok. Any other suggestions as to where I can look for bad or corroded connections. I should mention to it seems this current issue started after my drivers side floor board got wet from my sunroof leak.

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I would like to change the relay which controls the fan motor. Can someone tell me the number of the relay that controls the fan.
There is no relay in the blower motor circuit. You might try removing and inserting (several times) the 30A HVAC BLO fuse in the underseat fuse box.

I checked the connection at the fan motor it looks to be ok. Any other suggestions as to where I can look for bad or corroded connections. I should mention to it seems this current issue started after my drivers side floor board got wet from my sunroof leak.
There is a slim chance you could have a faulty/corroded chassis ground block connection caused by moisture wicking up via the carpeting. Check the chassis ground block connections behind the bottom front door trim at both front doors.

I say slim chance because if a chassis ground block was the problem, I would expect other vehicle systems to be exhibiting problems.

Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

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